# Total Restoration of a 1959 Superlead from 1973



## Matthews Guitars

I'm not sure if this qualifies as building or repair, but for some time now I've been working on a project to completely restore my VERY crusty 1959 Superlead from 1973. 

I'll be adding photos to this topic later but for now, just a quick introduction and rundown.

I bought a rather sad looking Marshall Superlead a couple months back that still had the original filter capacitors in it. Or more properly, after scraping off an amazing amount of filth and grime and dust, I found old capacitors hiding underneath. 

The cabinet isn't in great shape and, now I know, had been recovered at some point. And then immediately sprayed in white enamel on top of that. I tried everything and nothing would take the paint off that wouldn't also wreck the tolex. So eventually I just stripped the cabinet. In doing so that's when I discovered clear evidence that it had been recovered once already . The gold trim line below the small Marshall logo was the wrong size and type and was just glued in on top of the original trim line, and original tolex was still under that trim line. There are damaged spots all around the edges of the cabinet that were patched with filler. It had some unusual plastic corner protectors on every corner, a type I've never seen before or since. The feet, corners, and handle had all been painted brown and I'll have to say that the spray paint work was well done. But all the gold piping and trim was only gold because it had been hand painted with a brush with gold paint. It probably looked pretty good after being freshly painted and put together...but when I got it, it just looked like a mess. 

I'll redo the cabinet myself, when I have time for it. I just decided that for my purposes I'd have Sourmash build me a new cabinet for it. I'm going to hold back on what I got for a later post. It's nice, I'll say that. Sourmash does GOOD work. Highly recommended!

Judging by the amount of dust, dirt, and grease that was stuck hard to the chassis, I'd have to say that this amp must have spent the last 20 years in a garage and a very dusty one at that. 

Both the front and rear gold panels have lots of pitting corrosion on them. That takes a pretty abusive environment to do that. And most of the lettering and legends was worn/weathered off. That actually is what started my project and new venture to create and offer brand new replacement metal panels for JMP metal face Marshalls. A project that is about to put my first production examples in my hands in just a few more days.

At first, I replaced the capacitors and serviced the amp. And I ran it for a while. Got familiar with playing through the beast. Loved it. Will love it again soon.

It had a master volume mod added to it, but added in place of an input jack. I approve, no holes added.

The saving grace of this very dirty old amp was that aside from being positively filthy, it was all original with no irreversible mods done to it. The impedance selector jumper socket was disabled, with the individual transformer taps being assigned to specific output jacks, which were labelled, albeit with a permanent marker. Fine, that's not unreasonable and actually very functional. I'll probably opt to stick with that setup and make a special back panel that is marked to match, thus making it look like a rare factory option that never existed. 

To clean the chassis took nothing less than a scraper to get the gunk off it. And under the gunk I found a few rusty spots and ALL the zinc galvanizing had gone dark grey to black. This was just not going to satisfy me. 

So I made the choice to do the full restoration. 

The chassis has been COMPLETELY stripped out, going so far as to drill out the rivets holding the tube sockets in. 

The chassis has been sanded clean and smooth with just a little bit of rust pitting left on it to bear witness to its history, and it has been re-galvanized and yellow zinc chromated, to original factory specifications. 

The transformers were partially disassembled (covers taken off) to reveal that they'd been serving as roach motels for many years. They got a good cleaning and I had the covers blasted clean and they also got re-galvanized and clear zinc chromated to original specs. 

The transformers were sent off to Mercury Magnetics to be tested, baked out to remove moisture from the coil formers, revarnished, and have their leads replaced with new, leaving generous lead length to allow room for a really good lead dress job. They should be back soon. 

All the small metal parts such as tube clamps and the transformer screws and clamps have also been blasted clean and galvanized to original specs. 

Some of the original brass screws were already broken or broke when I went to remove them due to metal fatigue. All new brass hardware has been obtained to replace them. 

This amp, being a late 1973 build, just missed the days of point to point wiring. It has a first generation ST1 board. It was filthy but not as dirty as the top of the chassis. The board was removed, carefully cleaned, and the capacitors that had been replaced in the past that would originally have been mustard caps were replaced with original mustard caps. (Just five on the board, the rest were still there.) The solder traces were carefully cleaned and resoldered with good flux, and cleaned again. Due to corrosion some traces had to be repaired by bridging wires soldered across those traces. The repairs are sound. 

It's getting all new tube sockets of the original type (NOS examples) and mounting system, with snap rings. I have lots of those in stock. The new preamp tube sockets will be upgraded to ceramic types, and will be riveted in as per original factory style. 

If I have a need to replace any components, every effort will be made to source original types, such as Piher resistors. 

Once the transformers arrive and I get the chassis back from the plater's next Tuesday, the reassembly will commence. 

The goal is to bring this amp as close as possible to being as it was in 1973. I've only made one change, a cosmetic choice, but one that was an available option in 1973. I'll leave that as a surprise when I post photos.


----------



## South Park

It sounds like great job you are doing . Go for it


----------



## Amadeus91

Like a Phoenix she will rise again and roar.
Look forward to your progress and success in breathing new life into her.


----------



## Matthews Guitars

The first four photos show you what I had to start with. I doubt you've seen many Marshalls that had more dirt on them short of salvaging them after a natural disaster like digging them out of a mud slide or a burned nightclub.

The last three show the SAME chassis, transformer covers, and small parts now. 

Actually the chassis was sent back to the plater's because they didn't apply the requested yellow chromate coating, and so I'll have that back in a few days.


----------



## Matthews Guitars

And this is what it will be going into when it's done!


----------



## Matthews Guitars

Here's the chassis, fresh back from regalvanizing with a fresh coat of yellow zinc chromate. 

Note that there are still some small pits visible in the upper surface. I elected to leave those in there as evidence that this is an original restored chassis, and not a reproduction or replica.


----------



## herbvis

Was that pricey?


----------



## Matthews Guitars

I had the chassis redone along with the transformer end bells and most of the small metal parts for 200 dollars. I think that's fair. The parts that were clear chromated had to go in a separate batch. And there is a batch charge for each process requested. So one for yellow chromate, one for clear chromate.

When all the parts arrive (the transformers are at Mercury Magnetics getting tested, baked out, and revarnished, plus new leads) then I begin reassembly. It's going to be fun and will actually qualify as my first full amp build in more than 20 years.


----------



## Guitar-Rocker

Nice touch on the replating, I'm sure it will make reassembly more fun now, and it will definitely look as good as possible


----------



## South Park

Nice job


----------



## neikeel

I must confess that when you started the project I wondered why all the effort. Personally I really like amps that are lightly worn and have a patina to them, I can build new amps all the time. 
However looking at what you started with and where you are going I think it will be a great restoration. I am very familiar with this type of work as for many years I used to restore old motorcycles. 
I hope you are practising your wire lacing technique to get all the runs correct.


----------



## Matthews Guitars

My 2203 is "lightly worn with patina" and I'm cool with it like that. I actually want it to stay just as it is. But the 1959 was the victim of neglect if not outright abuse. And since I have definite plans for it, as a showcase for my restoration metal panels, I want it looking as sharp and fully restored as possible. So I decided that restoration would be appropriate. 

The original cabinet had been recovered at some point in the past...and immediately spray painted white with enamel. Nothing on earth would get that enamel off without ruining the tolex underneath. When I stripped it I found plenty of evidence that it was previously recovered. Such as the original gold string still in its groove and still sitting on top of tolex. The previous guy to mess with it had just cut the tolex off and glued a new string down over the old one. What a hack job. 

I'm not going to say that I won't be offering "frame off" restoration level services, too. 

Between myself and some people I know, we have the capability to restore a heavily hacked, modded, and drilled out Marshall chassis to its original specifications and glory. If someone has a modded '68 Plexi and wishes that its OT transformer window hadn't been hacked out by some maniac with a hole saw or a plasma cutter to fit a Magnavox TV transformer in it, I'm the man to talk to about restoring it to as it was. The damaged area can be cut out and a new section laid in, cut to original transformer cutout specifications, welded, ground flush, finshed to original appearance, and then regalvanize it. It'd look like it never happened. Any hole from small drill holes to transformer cutouts can be made to disappear.

In fact I'm looking for a hacked chassis or two to practice on. Just in case you know someone who has a butchered Marshall that needs to be brought back from the dead.


As for wire dress, I'm a disciple of Dave Reeves (Of Hiwatt fame) and I have a mentor who is a maniac for wire dress. It'll be a fine job.


----------



## Goldfinger

I had two '73 hand-wired JMP Super Lead 100 heads that I purchased for $500.00 each. Selling them was the worst _gear sold_ decision I've ever made.


----------



## Matthews Guitars

It hurts just to read that. But then again, I've heard stories of pawn shops refusing to give more than a hundred bucks for a JMP Marshall, back in the mid 80s. Around the time I bought my first real amp, a Fender Pro Reverb (also a '73 model) for 75 bucks.


----------



## Matthews Guitars

Well, it's apparently going to be several weeks before I get my transformers back from Mercury Magnetics. No problem, there's plenty to attend to in the meantime. I guess I can start on stripping a 1960 cabinet and preparing it for its rebirth in purple levant with gold trim and Bluesbreaker grille cloth.


----------



## Matthews Guitars

Here's the head cabinet along with the freshly redone 1960A cabinet I completed yesterday. Working on the bottom cabinet now.


----------



## MarshallDog

Dam man, this is very interesting and you do some very spot on detailed work...Marshalldog likes that. Where did you and how did you find a place to treat the end bells and the chassis??? The cabs look great!!!!


----------



## Matthews Guitars

There's a plating shop in Pompano Beach, FL, that does hot dip zinc galvanizing and also clear and yellow chromating. (Done after the galvanize dip is done.) They did my work for me. But it's far from the ONLY plating shop around that can do this. Just google for "Galvanizing service" and you'll find lots of hits. There's probably one in your general area. 

Where there is manufacturing of steel products, there is a galvanizer nearby.


----------



## Amadeus91

^^^^Just typed bad ass into google and your name came up as a first hit.^^^^^
Outstanding work.


----------



## Matthews Guitars

I cut two back boards for the cabinets last night, out of 13mm Baltic Birch. I don't like particle board and those original backs are deteriorating anyway. No sense in keeping them. 

The bottom cabinet had a high water mark on it, about three inches up. Speakers are fine. I suspect that water related issue may have led to the glue joint failures. It could at least be a contributing factor, and it's one that sure isn't good for particle board.


----------



## paul-e-mann

Matthews Guitars said:


> I cut two back boards for the cabinets last night, out of 13mm Baltic Birch. I don't like particle board and those original backs are deteriorating anyway. No sense in keeping them.
> 
> The bottom cabinet had a high water mark on it, about three inches up. Speakers are fine. I suspect that water related issue may have led to the glue joint failures. It could at least be a contributing factor, and it's one that sure isn't good for particle board.


Very interesting project, I'm looing forward to the amp rebuild.


----------



## gldtp99

Great project !!!

Here's my '73 Superlead as I first got it:





















I installed a new Metro/Heyboer PT and got everything working properly (parts replaced as needed to work 100%) and put a new logo on the head cab.

Now it's a great sounding, but used looking old Marshall.

Nothing approaching the detailed restoration you're doing.

I salute your skills, attention to detail, and the lengths you're willing to go to in your '73 Superlead project !!!


----------



## Matthews Guitars

Second cabinet's done. Once I put in the handles which arrive tomorrow, and give it a final cleaning.


----------



## Matthews Guitars

A quick before/after on the chassis.

First pic is the chassis in "as received" condition.

Second pic is the same chassis after strip-down, regalvanizing, rechromating, and the start of reassembly.


----------



## Filipe Soares

man... your post made me want to refresh my major... at least new tolex!


----------



## South Park

A restored Marshall like that is a real rare amp.


----------



## Matthews Guitars

I can recover your head cabinet for you if you want. I'm only getting better and better at it!

I have black elephant tolex in stock, plenty for a few heads. And I have purple, and bright blue, and even blue snakeskin as well. Plus I can easily get any pattern that's currently made.


----------



## ampmadscientist

Matthews Guitars said:


> A quick before/after on the chassis.
> 
> First pic is the chassis in "as received" condition.
> 
> Second pic is the same chassis after strip-down, regalvanizing, rechromating, and the start of reassembly.
> 
> View attachment 63151
> View attachment 63152



You did a really nice job on the chassis. It takes a lot of commitment and work to reach that level of restoration.


----------



## Matthews Guitars

OK, wrong amp, I know! This is my 2203, not my 1959, but it now sports one of my first run reproduction back panels. This one features an effects loop occupying the two inward speaker jacks and the added rotary switch is the impedance selector for the remaining two, Which I will mark later with clear Dymo labels with black print. 

I think that I'm going to do a slight print revision and bring the legends along the top edge down a little bit so they have more clearance off the back cover. 

I just need to stamp in the serial number and call it done.


----------



## Matthews Guitars

I was able to acquire a very rare original Marshall NOS front panel for a 1959/1987, and by virtue of having done so, I've been able to substantially improve the accuracy of my artwork. Just in time for the second batch of front panels to be printed, too! (The first batch was expected to have "issues" and I was right about that. I don't intend to sell any from batch 1. Well, maybe at a deep discount if you don't mind a couple of small inaccuracies. But for a highly authentic restoration, you'll want front panels from batch 2 or later.


----------



## Matthews Guitars

Here's a transparency printed with the artwork, laid over and slightly offset, from an original panel. This shows how accurate the artwork is.


----------



## neikeel

That looks really good - I’ll be wanting at least one of those front panels.
Do you think you will be making any 50w rear panels? I had an original one and sold it, now I need one.


----------



## Matthews Guitars

Yes, if I can verify the correct layouts. Since I don't have a 50 watt chassis available to me as of yet, other than one that has been modded a lot, I'm mostly working from photos and measurements I've collected.

If you send me your email address, and a note, I can send you a 100 percent scale pdf of the appropriate file. Print it out at full scale and compare it to your chassis and you can then tell me what's not right about it and what changes need to be made. I'll then respin it and send the updated file. When you say "That's it!" then that version goes to print and punch. 

Want one where all the legends go to eleven? I can do that!


----------



## Mick10

Beautiful work on a great project. You have some rare skill


----------



## Matthews Guitars

Here are the seven types I've sent to print so far. There will be others and I've got revisions done on the front panels. The I and II legends are badly spaced and the font is wrong so that has been corrected. And the input holes on the rocker switch front panel were punched a bit off position. Also fixed for the next print run.


----------



## nkd

Good job, the cabs and chassis look great.


----------



## Matthews Guitars

And I got notice that my transformers are now being shipped back to me. Should have them next week. Reassembly will begin immediately.


----------



## DrAndy

Wow. That is a whole new level of detail. I love it - tremendous restoration.


----------



## Matthews Guitars

I appear to have made a mistake. I entrusted the (re)build of this amp to a friend of mine who's been doing amps for 45 years.

Well, due to issues with his medications that he's been on since just recently, I'm getting incredibly slow work out of him. He's always been slow and methodical but as of right now he's had the amp for literally two and a half weeks and has not yet wired in the transformers! 

I'm running short on time. I plan to have that restored amp on display at the Orlando guitar show on Jan 31, Feb 1 and 2, and that gives me just four days to get it completed, testing, biased, and running. 

I'd planned for HIM to do the work while I try to complete a new built Matthews guitar for the show but it's starting to look like NEITHER will be done in time.

I've abandoned the guitar and will have to take over the amp rebuild myself. 

This kinda sucks.

But on the brighter side, I've got about 75 assorted reproduction Marshall metal front and back plates in stock and ready to sell. 

I'm going to bring that 1959 to the show even if it's a non-running amp for display only. Interested people can still see all the restored metalwork.


----------



## MarshallDog

Matthews Guitars said:


> View attachment 64815
> 
> 
> 
> Here are the seven types I've sent to print so far. There will be others and I've got revisions done on the front panels. The I and II legends are badly spaced and the font is wrong so that has been corrected. And the input holes on the rocker switch front panel were punched a bit off position. Also fixed for the next print run.



Looks really great, good job! I believe you will be selling a lot of those!!


----------



## harleytech

*


----------



## Matthews Guitars

I've added rear panels for Super Bass and Tremolo models plus rears of every type that include the punch for voltage selectors.

I've chosen not do the Bulgin power connector punches at this time. Probably in the next batch I'll add those.

For those who have amps that used to have a non-detachable power cord or a Bulgin socket, which has been changed to an IEC of some sort,
I recommend using the fixed cord version and you file out the hole to fit your specific installation as there obviously is no standardized solution for the socket retrofit. Every person who has done that has figured out his own way of doing it.


----------



## Matthews Guitars

Aside from making a new back cover for the cabinet, the restoration is complete. 

Since I plan to leave the cover off it for the duration of the guitar show i'll be exhibiting at this weekend, to show off the shiny restored chassis,
I'm totally happy to let the back cover wait until later.

Today I spent some time doing a shakedown run on both my Marshalls. Being in the same small room, even with good hearing protection, with a pair of absolutely decked Marshalls is physically tiring. It was really the first time I compared the 1959 to the 2203 side by side. And I don't know which I actually like better. They both sound like Marshalls. The 1959 has a certain clarity to it even when it's at bug smashing volume levels, while the 2203 has a raw richness that's different and yet equally appealing. 

Gain wise, i'ts really not a whole lot different between the two. The 2203 is a bit hotter but not a lot. Neither is high gain by modern standards, nor have had any expectations to the contrary. My Seymour Duncan Pickup Booster pedal provides a nice clean gain boost that easily moves things into smooth overdriven sustained single notes territory and that is quite good enough.

I like them both. I don't have to choose since I plan to keep both. But if someone offers me an excessive price, I might sell one. And use the money to get another and restore it.


----------



## Matthews Guitars




----------



## Filipe Soares

you know that this thread is absolutely pornographic, do you? 

totally amazing!


----------



## MarshallDog

Matthews Guitars said:


> View attachment 66817
> View attachment 66818



Amazing job, looks wonder!


----------



## Matthews Guitars

The photos show me that I need to do a few touchups on the tolex in the corners. No problem, I have some matching acrylic paint that'll clean them right up.


----------



## stickyfinger

You need a heat gun to get the corners to mold around the roundovers. One slit and work the tolex. 
Personally, that tolex job need a professional touch.


----------



## Matthews Guitars

I got much better as I did more of them. Actually they were super tight when I did them but even though it's only been a few months, I've had some issues with the tolex shrinking. I had to redo the face of the head cabinet because the center slit where the gold string rests had expanded to a quarter inch gap. 

It could be that the contact cement I used causes shrinkage. So I should find a type that doesn't do that.


----------



## neikeel

Also the type of vinyl you use is a factor. Genuine Marshall stuff does not shrink. The orange stuff used on 71 SL resto has shrunk on the string lines on top where it had got very hot.


----------



## Matthews Guitars

A note on the Marshall restoration panels I'm making:

At this time I am only making types for JMP era amps. This means that I am not making ANY front panels that are for the later JCM 800 types, with their full width front panels. All my front panels are 17 inches wide. 

My rear panels are all (at this moment) 25 inches wide for 100 watt models only. I'm finalizing the design work to add rear panels for 50 watt models. 

I plan to offer certain JCM 800 edition front and rear panels in the future. As I get accurate data to allow me to make them I will design them. 

I'm focused on 100 and 50 watt model heads first. I'll branch out to combos and smaller amps as time goes on.

I'm working on getting set up to make plexi edition panels as well. I am searching out a commercial painting shop that will be able to apply the gold metallic back coating on the panels. I have samples of original panels coming to me so I can match the gold paint color as exactly as possible. 

If you have a 1968 Super Lead, Super Bass, or Super Tremolo model in need of a highly authentic reproduction plexi rear panel for it, I will soon be able to provide you with just such a panel, one that will satisfy the most discerning collector/historian.


----------



## proxy

Wow me likey ....


----------



## Matthews Guitars

Just to get all the photos together in one place, for this now completed restoration project, here's the before/after pictures that tell the tale.







(I know, I can stand to improve the head cabinet tolex work a little. That's OK, I can redo it at any time.)

Chassis and hardware are the original parts. Transformers are the original parts. Front and back faceplates are my new reproductions.

Of course it's been recapped. Internal components that were wrong were replaced with period correct types and values. Mods were reversed.


----------



## Ramhead

You did a good job making a vintage amp to looks like a reissue.


----------



## Matthews Guitars

No, I did a good job making a ratty old amp look like it did when it was new. 

If it had been LESS rusty, LESS crusty, and LESS neglected, I'd have done less to it. I don't restore an amp to this level if its starting condition is better.


----------



## Ramhead

Someone on the old "Plexipalace" forum had a great signature : "Keep those things original, boys".
Yeah it was crusty.. so what. It showed its age. You could clean it and keep it original.. now it just looks wrong.


----------



## Matthews Guitars

You are free to do whatever you want with the amps you own. I'll decide which ones I own that will be kept as they are and which are restored.
I'm currently restoring a 1970 Super Lead that was so heavily butchered that there are not less than 86 (yes, eighty six) holes in it that were added or were ground out larger with a dremel. All those holes are being welded over and/or restored to original dimensions and locations. When the work is done there will be no trace of that DAMAGE. 

That's really going to be the proof of concept. To be able to truly reverse the DAMAGE done by hacked-in modifications.

I'm not out to erase the history of amps that have an interesting history. But those that have been abused and neglected and aren't "cool", just "totally ratted out" can be brought back.


----------



## Matthews Guitars

The guts after completion:


----------



## Matthews Guitars

I've sold a small number of my restoration panels to a few individuals so far. 

Feedback on all of them has been great. They love the product. They love having their amps looking sharp and youthful again.


----------



## DaDoc

I'm a vintage amp lover, and I think the restoration job you did on that '73 looks AWESOME! 

Great job!


----------



## Matthews Guitars

If you think that was a lot of work, I'm now doing a restoration on a 1970 Super Lead that was much, much, MUCH worse to start. 

Here's some photos of it "as received". 






There were 86 (Yes, 86) holes added to this chassis that are non-factory, or holes that were badly enlarged by someone with a die grinder.

Those have been welded up and reground and right now this chassis is at the machine shop getting some holes recut.


----------



## neikeel

Matthews Guitars said:


> If you think that was a lot of work, I'm now doing a restoration on a 1970 Super Lead that was much, much, MUCH worse to start.
> 
> Here's some photos of it "as received".
> 
> View attachment 70622
> View attachment 70623
> View attachment 70624
> 
> 
> There were 86 (Yes, 86) holes added to this chassis that are non-factory, or holes that were badly enlarged by someone with a die grinder.
> 
> Those have been welded up and reground and right now this chassis is at the machine shop getting some holes recut.



Looking forwards to an update on this soon


----------



## Matthews Guitars

Me, too. I've got every part ready for it, I'm just waiting for the machine shop to complete their work. Then it comes back to me for final surface finishing and checking,
before going out for galvanizing and chromating. When it comes back I start reassembly.


----------



## ampmadscientist

Matthews Guitars said:


> Me, too. I've got every part ready for it, I'm just waiting for the machine shop to complete their work. Then it comes back to me for final surface finishing and checking,
> before going out for galvanizing and chromating. When it comes back I start reassembly.



What would it be like if it were solid gold plated?


----------



## Matthews Guitars

More expensive! A waste of money I'm not going to part with! I would not see the point in going that far on the chassis that would be hidden inside the head box in normal use. 

If someone wants me to gold plate his Marshall chassis and finish it to absolute perfection, I'll do it...but I'll make thousands in profit and get paid in advance or it won't happen.


----------



## Matthews Guitars

Here are some comparison pics between one of my replica panels for a 2203 (the panel shown has incorrectly sized rectangular rocker switch holes, an error by the sheet metal shop) and a very rare unpunched ORIGINAL 2203 spare panel direct from Marshall. 

This will allow me to get the JMP logo exactly right on my panels and I'll be adding the serial number block on the front panel as another variant for those who want it.


----------



## QLYDEmusic

Matthews Guitars said:


> View attachment 62556
> 
> 
> 
> And this is what it will be going into when it's done!



So Beautiful and it’s going over one of the best amps ever made


----------



## neikeel

I got all excited that we might have build pics!

I’ll have to post my latest instead.........


----------



## Matthews Guitars

Finally, some pretty GOOD photos of the panels. I had to rethink my photograph approach and it worked well. To get even illumination in the sunlight I had to back off so the sun angle varied less across the panels. I ended up standing some distance away and used my monster zoom lens.


----------



## Matthews Guitars




----------



## Matthews Guitars

I want you to know, the panels shown here do not represent my full catalog of panel types. I have others that aren't shown.

Give me the configuration you need and I probably have it.

I have noticed that there's an error on every back panel shown that has selectors for both speaker impedance and line voltage. The line voltage
legend is wrong and will be reprinted to read MAINS as it should.


----------



## neikeel

As promised - one of my Covid-19 recovery week builds whilst we are waiting for Chris's restoration, I had to use a new Valvestorm chassis as I don't have the metal shop that he has access to:












Note the unused extra socket. That will get its own board which will contain its own cascaded preamp that will be activated via the low II channel so you can switch between stock Superbass and 2203 (albeit with SB tone stack and NFB). I made a similar one for my son but used 6550s in his, it works fantastically well, hence this build using EL34s. Basically using a lot of spares I had lying around, the LCRs are from a bundle I have. They fully reform to spec within a couple of hours. 
As you would expect it is classic Superbass. Loud and punchy but crunches and gets dirty as you turn it up on the dial.


----------



## coolidge56

Matthews Guitars said:


> If you think that was a lot of work, I'm now doing a restoration on a 1970 Super Lead that was much, much, MUCH worse to start.
> 
> Here's some photos of it "as received".
> 
> View attachment 70622
> View attachment 70623
> View attachment 70624
> 
> 
> There were 86 (Yes, 86) holes added to this chassis that are non-factory, or holes that were badly enlarged by someone with a die grinder.
> 
> Those have been welded up and reground and right now this chassis is at the machine shop getting some holes recut.



Oh good lord!


----------



## Matthews Guitars

That '70 chassis is now on the way to get a fresh zinc galvanize and yellow chromate job. A few more days and then I can get down to the business of rebuilding the amp.

Neikeel, that is a fine looking machine there. Love it!


And now for my next trick, I'd LOVE to get connected to the ORIGINAL source of Marshall's metal face gold anodized panels, if they still make the same exact product. That'd allow my front and back panels to become even more authentic and correct.


----------



## Matthews Guitars

I've decided to do something utterly bizarre, with the '74 Super Lead I picked up that will become my one 80s modded Marshall.

It's going to become a reversed colors purple and gold head. 

You've seen purple Marshalls before.





I found that I can get GOLD tolex. I have some on order. 

I make my own front and back panels. 

So, this head will be done with purple panels with gold lettering, in a gold tolex plexi headshell, with purple piping and trim.

It'll be kind of unique.


----------



## Matthews Guitars

Some of my original parts got lost while out for galvanizing. All six capacitor clamps, to be precise. Anybody got any "vintage" cap clamps for an old JMP that I can buy?

I have a couple other little parts coming and then the reassembly begins in earnest. 

On the repro panel side of things, I've made arrangements to start making the most popular models with screen printed artwork rather than digital printing, but the less
popular types will continue to be digitally printed because the cost of setting up silk screens and getting the screening done is significantly more. Once the screens are
done and ready for production, it still costs me more than double the per-unit price to get them digitally printed. 

And I'm always looking for an aluminum brush finished, gold anodized material that is more exactly like the stuff Marshall used during the 70s. The quest for a higher level
of authenticity will not end until my products are indistinguishable from the originals aside from their new condition.


----------



## Matthews Guitars

The missing parts turned up, thankfully. Once they're back from plating, reassembly really begins.


----------



## Olli Harkoma

Very nice work. I would have myself a -71 JMP Super Lead that I would like to restore. Original power socket and mains voltage selector missing.


----------



## Matthews Guitars

That one looks like it's been close to a fire! On reverb there's a guy who's selling a power transformer that's probably what you'd need. It's a 70s transformer, but may not be a '71. The correct transformer clamp brackets are available from valvestorm. For replacement front and rear metal panels, you go to ME. I make them. 

If you want to do the full deep metal restoration on the chassis including welding up the extra holes and punches, I can assist. I have a shop that does that work for a very fair price. The expensive part is the assembly and disassembly. 

I haven't gotten around to rebuilding my '70 yet, but actually it turns out that it's a '69. I'm acquiring a few more vintage correct parts for it before starting the reassembly. 

I want ONE of my Marshalls to be the full blown California 80s modded Marshall. Arredondo or Cameron Atomica mods. (Probably Atomica.) I'm undecided whether the '69
will become the mod platform or if I'll re-mod my '74 which was modded before I got it, and has lots of extra well placed, nicely done holes and an added preamp tube, but frankly as mods go, it's really not good at all.


----------



## dragonvalve

Wow. This is fine attention to detail!

Was looking for what to do with touching up the back mesh panel on my 2555SL and found this thread.

The plating on the mesh panel is not bad just fading in some areas and getting cloudy in others. I just touched up some very minor rust around the screw areas with rust converter and a Q-tip.

Looks like the plating done on the MG rebuilds, chassis and other metal parts is much better than the factory.


----------



## neikeel

Last entry was September. 
Chris must be due an update!!!


----------



## Matthews Guitars

Yes, it's time for an update. But first things first. Neikeel, is that one of my back panels on your Valvestorm build? If so, I need to alter the location of the legend on the power receptacle so that the Bulgin connector doesn't cover it up. 

I needed to wait until I found what I believed to be the most correct preamp tube sockets for this amp that I could get. And FINALLY, just a few days ago, I got them. EBY TS102 9 pin shield base, center contact, true NOS. Got a bunch of them. 

Because the preamp tube sockets were literally the first thing Marshall put in the chassis, and riveted them in, I did exactly the same thing so the NOS preamp sockets are now installed and I'm installing the original Amphenol octal sockets. (After making sure all the contacts have good grip.) 

I'm having a lazy evening but I plan to get the transformers, capacitors, and sockets mounted by the weekend.


----------



## Matthews Guitars

Caps are installed, transformers are installed, , and my new set of brass shaft, brass bushing CTS pots just arrived, which will go right in tonight. And that'll mark the point where I can start to think about wiring the board into the amp. It's not going quickly. I'm in no hurry. I want it to just be RIGHT the first time I turn it on.


----------



## neikeel

Matthews Guitars said:


> Yes, it's time for an update. But first things first. Neikeel, is that one of my back panels on your Valvestorm build? If so, I need to alter the location of the legend on the power receptacle so that the Bulgin connector doesn't cover it up.



Sorry, I missed that - no it is not one of yours. I've had it for years (can't remember where I got it from, same as the original spacing IIRC!


----------



## dragonvalve

Me excited to see the results!


----------



## Matthews Guitars

I could use a little assistance. Help in getting some really good clear photos of an unmolested example that dates from, apparently, 1969, which has an upright power transformer, which has the additional tag board near the fuse holders, which has a dark brown main board with solder turrets, which is not a grid perforated board. 

Photos of such an amp would help me to get the power supply sorted out properly as I rebuild it. 

The amp as I got it came with a large solid state rectifier pack. I'm not quite certain that it's even correct for this amp.


----------



## neikeel

The earliest 69 amps had either a set of diodes on a chassis mounted dedicated board or, slightly later a diode block on the chassis. These all had perfd ‘short’ circuit boards. The later more fabric dark boards with snubbers and diode block are characteristically 1970 (before the cream colours boards).


----------



## Matthews Guitars

Update with photos. 

Chassis parts mostly assembled to it. still researching the nuances of power supply wiring for this one. Yes, this has the full wave bridge rectifier diode block on the chassis, but apparently that mounting hole got accidentally welded over during chassis reweld and repair so I'll just have to relocate and redrill the hole. The least of my problems!

To start off, let's look at what I started with. And what it has become. Just a few photos out of many I took.


----------



## Matthews Guitars

As you can see it's never ever going to be a perfect representative of a '68 or '69 plexi but it's a far cry from the shotgun victim it was when I got it. 

Evidence that it was originally a true plexi: Under the metal panels it came with (the back one was aluminum treadplate!) there was glue residue with gold paint still on it. 

I realized that the guys at the sheet metal shop were overzealous when doing the fills and covered up the extra hole (leftover from the GZ34 rectifier socket punch that remained from earlier days) next to the one filter cap next to the transformer. I COULD repunch that hole but I'll probably just put the steel cover disc in place and call it good. 

Neither the PT nor the OT is original. It had...some random transformers...on it when I got it. But, hey, the choke was original, along with one resistor on the main board! 

The OT is a Merren, the PT is a Dagnall (Or is it Drake?) DET-4145H. I think that's a bit too new for this year build, but what the heck, it'll run. I can always seek out a more correct one later. 

You'll note that I've installed (Riveted, like factory) the fourth preamp tube socket. All the preamp tube sockets are vintage era correct, true NOS EBY 9 pin shield base sockets exactly like I've seen in some Marshalls of the late 60s-early 70s era. Lacking any more detailed information on "period correct" sockets, they seemed to be by far the most appropriate choice. Plus I've got about 50 more of them...why not put some to use?

The fourth preamp tube will be used. I plan to build this as a "factory hot rod", as if Marshall had decided that more gain was the right thing to do back in '68. Looking for a very "brown" modded plexi sound, but without adding extra controls, switches, pots, jacks, etc to the build. 

I intend to reuse the leftover DIN jack location (For a tremolo switch) for the footswitch for basic channel switching. (Gain boost switched in.) 

This chassis in its original form was a bit of a hodgepodge. Six holes up front for your usual presence, bass, mid, treble, and 2 volumes, but the rest of the chassis was punched for a tremolo unit. Tremolo footswitch jack punch in back. Punched for four preamp tubes, and for a GZ34 rectifier socket beside the power transformer, and also beside that one lone filter capacitor in that corner.

I attempted to preserve all ORIGINAL holes in the chassis and have the after-the-fact holes welded up and covered over. Some of those were missed, some original holes got covered. Oh well. No big deal. I can redrill and repunch what was covered by mistake and I'm not going to worry about added holes that didn't get covered.


----------



## Matthews Guitars

Wiring up the chassis is about finished. I need to populate the board with all my NOS components and then it'll be ready to wire in. 

Unfortunately the original full wave bridge rectifier failed. I went to solder a lead to it and the terminal just popped out. No fixing that. 

I replaced it with a perfectly good substitute but I'd rather obtain an exact match original if possible.


----------



## Matthews Guitars

I have to say, I'm really looking forward to getting this amp together and running. But the question is, considering what I started with, and what's going into it, to what extent is it going to be a "true" Plexi? As long as it sounds right, can I call it that? Its originality is limited to the choke, the chassis, and both the phenolic boards in it, minus the components. Nearly all the components going in are true NOS originals of the right types (but maybe not always the right date codes) and the transformers are a new Merren OT and a good Dagnall T4145 PT which is considered to be a great choice for a plexi. 

It's basically a new build using NOS parts and original hardware. (SOME original hardware.) 

I've made one intentional construction change to it. Since I'm not bothering to include a death cap on the extra terminal board near the fuse holders, I've elected to repurpose that board as the primary voltage selector section. The amp never had a mains voltage selector so why not? It's neater and more useful than just leaving the unused primary taps hanging loose. And switching voltages will be as simple as moving the jumper from the 120 tap lug to whatever one you need.


----------



## Matthews Guitars

Actually I found some Superbass photos at amparchives which tells me that my choice to assign that small turret board to voltage selector duties is actually correct. I've found so few photos that showed this clearly. None until now, actually. 

But I have to be careful when using Superbass photos as there are some differences. I need to be really sure that I'm working from the CORRECT photos to get the parts layout on the board correct. 

Here's the board type I'm working with and will be reworking mine to match. Not counting the rectifier board beside it.


----------



## Matthews Guitars

A few update photos, and my workbench, which I try to keep clean, orderly, and functional, even though the rest of the garage is borderline "EPA Superfund Site". 

I'm looking for a CORRECT layout for this specific board and amp variant. Going by photos found on the amparchives and other sites, I keep finding differences. Different value resistors, different capacitor values....I need the truth. I never had an authentic reference for this amp, given the state it was in when I got it.


----------



## neikeel

Ah, you need to swap the 68k grid turret to where the hole for the wire is sitting over it loosely now (the angle goes to the right to make space for the 0.68uF/2k7 RK combo) ie both pairs of 68k should be same length. 
Do you intentionally want both plate resistors in pi at 100k. If you need an 82k Iskra just let me know. I probably have 47k iskra


----------



## Matthews Guitars

Can you give me directions? I'm not yet THAT familiar with the layout.


----------



## Matthews Guitars

Do you mean, the point at which the two 68K grid resistors meet, on the left side of the board? Move the turret one hole over and one hole down? Is that correct?

I think I can spare pulling a turret off the input power selector board. I believe it has an unused turret, maybe even two, that can be surgically transplanted.


----------



## Matthews Guitars

I have to admit, it's getting a bit frustrating trying to use board photos as build references. Because there are so many little variations between even similar boards.

I'm seeing boards like mine where even they have certain things that are different from one to the next. Such as, for example, the location on the board where the first two 68K input resistors meet in one turret. I've found at least three different board photos of boards that look essentially like mine, but all have the common terminal between those two resistors placed in different turrets.

Capacitors change from board to board as well.


----------



## cooljuk

Matthews Guitars said:


> I could use a little assistance. Help in getting some really good clear photos of an unmolested example that dates from, apparently, 1969, which has an upright power transformer, which has the additional tag board near the fuse holders, which has a dark brown main board with solder turrets, which is not a grid perforated board.



Do you still need these photos? I have good clear photos of at least four amps that check every one of those boxes in my reference library. If you do, email me and I'll reply with the photos. info@re-wind.net


----------



## Matthews Guitars

Her's the board as it sits now. ALMOST done. There are a few parts still to be added.


Do you see any errors? I know, the first cathode bypass cap is wrong. I'll deal witih that later.


----------



## TAZIN

The end of the first pair of 68K resistors; near the 820R resistor, where the Green grid wire attaches need to be moved to the other solder eyelet. Right now it's setup like a Super Bass.
Also, you have two 8K2/1watt B+ dropping resistors in series rather than a 10K/1watt & a 8K2/1watt.
Additionally, that 100K carbon comp plate resistor needs to be an 82K.


----------



## neikeel

TAZIN said:


> The end of the first pair of 68K resistors; near the 820R resistor, where the Green grid wire attaches need to be moved to the other solder eyelet. Right now it's setup like a Super Bass.
> Also, you have two 8K2/1watt B+ dropping resistors in series rather than a 10K/1watt & a 8K2/1watt.
> Additionally, that 100K carbon comp plate resistor needs to be an 82K.



LOL - see post #94


----------



## TAZIN

neikeel said:


> LOL - see post #94



You got me that time!..lol..


----------



## Matthews Guitars

Hmm...I guess I need an 8.2k resistor in place of that extra 10K. Love to get the right one. Off to check ebay!

I also need to see if I can find those red bypass capacitors that I don't have yet.


----------



## TAZIN

Matthews Guitars said:


> Hmm...I guess I need an 8.2k resistor in place of that extra 10K. Love to get the right one. Off to check ebay!
> 
> I also need to see if I can find those red bypass capacitors that I don't have yet.



For the 500pF caps Marshall used both the ceramic 'Dog bone' type and the mica type (typically 560pF) thru 1969 although the 'Dog bone' type became more prevalent as you work your way through 1969.


----------



## Matthews Guitars

Got any idea where to get enough of those red dog bone caps for me to finish this out? Brand? Type? 

As for that 100K resistor in place of the 82K...that was what was in place on one of the board photos I worked from. I've since put in an 82K, which I was surprised to discover that I have plenty of. I'm slowly building a stock of all resistor and capacitor values I'm likely to encounter in amp repair work. But of course, very little of that stock is vintage/NOS.


----------



## TAZIN

I rarely see those Lemco red dog bone caps available in the 500pF value...Those could take awhile to find.


----------



## neikeel

TAZIN said:


> I rarely see those Lemco red dog bone caps available in the 500pF value...Those could take awhile to find.



I had a big bag of 470pF pretty much used up. They had wide tolerances most measured over 500pF. 
I’ll have an extended rummage at w/e.


----------



## Matthews Guitars

I've got some really good 470 pf caps to use but when I find a proper red dogbone, I'll swap it in. Not going to let THAT keep me from running the amp!

The board is complete, the chassis is fully pre-wired, time to start inserting the brain in the skull. 

Just one more question comes to mind: I plan to run this with KT66 tubes. What's the desired value of the bias range setting resistor next to the variable resistor?


----------



## TAZIN

neikeel said:


> I had a big bag of 470pF pretty much used up. They had wide tolerances most measured over 500pF.
> I’ll have an extended rummage at w/e.



Interesting since the tubular ceramic caps are known for close tolerances and holding those tolerances for a long time.


----------



## stickyfinger

The 470p dogbones I picked up a few years ago were 20% tolerance. Unmarked and measured all over the place. Marshall used the 10% tolerance ones. Wonder what the typical measurement of those actually were.


----------



## Matthews Guitars

Since I've never found photos and/or wiring diagrams that are completely applicable to this version 1959 as of yet, which would show certain details I'm not seeing in any of them, I've got a few last minute wire connection questions that I need to find the answers for in order to complete this.

I need to know the connection points for both choke wires. I know one connection is a positive terminal of one of the filter caps. I need to identify where on the board the other one terminates.

Same for the red lead coming from the HT fuse holder. The tip. 

And, the yellow wire that jumps to all octal sockets. 

Once I have those connection points verified, I can start thinking about connecting it to my variac and start low voltage testing.


----------



## neikeel

Simple place to wire one end of choke to the common HT turret in the corner of the board. That gets a feed from the HT fuse, mains filter cap, center tap of the OT and the choke ‘in’. 
The other end of the choke goes to the same turret on the board as the screens hook up point (which in turn feeds the pi via the two series 8k2+10k 1w droppers.


----------



## neikeel




----------



## Matthews Guitars

Thanks. Image not working....?


----------



## Dogs of Doom

Matthews Guitars said:


> Thanks. Image not working....?


link:
https://t1.daumcdn.net/cfile/tistory/110A424F4ECF27F61C

also attached, it's a pdf


----------



## TAZIN

Dogs of Doom said:


> link:
> https://t1.daumcdn.net/cfile/tistory/110A424F4ECF27F61C
> 
> also attached, it's a pdf



Kinda similar to what Marshall did but not quite right.


----------



## neikeel

@TAZIN 
I wanted to indicate how the HT supply hooks up and the screen supply in relation to the choke, which is, I believe is how Marshall did it - or do you mean something else


----------



## TAZIN

neikeel said:


> @TAZIN
> I wanted to indicate how the HT supply hooks up and the screen supply in relation to the choke, which is, I believe is how Marshall did it - or do you mean something else



Sorry about that...What I should have said was that for his version of the '69 Super Lead Marshall was still using the '68 wiring layout.


----------



## TAZIN

One end of the choke gets soldered to the first B+ 10K/1watt dropping resistor along with the Yellow wire that feeds the grids on the octal sockets. The other end of the choke; along with the White OT center tap wire, go into a sleeve that gets soldered to one side of the Standby switch. The other end of the Standby switch gets a Red wire from the H.T. Fuse. At the H.T. Fuse typically you've got three Red wires. One Red wire goes to the output of the bridge rectifier and solders to one of the lugs on the H.T. Fuse. The other H.T. Fuse solder lug gets two Red wires one of which goes to the Standby switch (mentioned earlier) and the other Red wire goes to the mains filter cap located underneath the Standby switch.
In reference to the attached photo. The Yellow rectangle shows the Standby switch with the White OT center tap wire twisted together with one of the Black wires from the Choke. On the other side of the Standby switch you've got one of the Red wires (the one with the red circle around it) which comes from the one solder lug of the H.T. Fuse. The other Red wire hooked up to the same solder lug on the H.T. Fuse (a blue circle around it) goes to the mains Filter cap located beneath the Standby switch (circled in green).
The violet rectangle show where the other Black choke wire attaches along with the Yellow grid wire to feed the octal sockets.
NOTE: Normally the White OT center tap wire & the Black Choke wire that go to the Standby switch are usually run an a protective sleeve.
NOTE NOTE: I wrote this rather quickly so hopefully I didn't make any mistakes.....


----------



## TAZIN

Oops..Forgot to mention that a lot of these '69 amps have the mains filter caps in parallel with the H.T. Fuse. This means you've only have two Red wires at the H.T Fuse instead of three. One of the Red wires comes from the output of the bridge rectifier which solders to one of the lugs on the H.T. Fuse holder and the other solder lug gets a Red wire that runs to the one side of the Standby switch. The mains filter caps are fed from an additional Red wire which is soldered to the output of the bridge rectifier along with the Red wire that feeds the H.T. Fuse.


----------



## Matthews Guitars

It's together. It's running. I was very pleased that I had no current spikes or blown fuses or burning parts smells as I brought it up slowly on my Variac.

It's functioning as an amplifier.

But that's not to accuse it of functioning PROPERLY. It definitely has some issues for me to work through.


I found one resistor that was the wrong value...a full decade off. A 150K 1 percent resistor is NOT the same as a 15.0K resistor, though they can look very similar!

Despite that, the bias circuit is running about 100 volt range to the tubes and that's AFTER changing out that miscreant resistor. So....there's something funny there.

The tubes are biased so cold that they're heavily distorting. That goes along with the behavior I describe in the next paragraph, as the power tubes are well into cutoff, apparently. 

The volume control ALMOST acts like an on-off switch. I'm feeding the amp from my audio signal generator so I don't have to do double duty as a
guitar hero and a tech at the same time. 1 KHz signal going in, and when I just touched the bias pot, BAM, it got so loud that both my ears clamped down instantly. That's with the volume knob down just over 1. 

And what's with that 452 volt measurement on the high plate of the cathode follower? (V2) The voltage divider chain of resistors seems to not be doing a heck of a lot. That implies a high circuit impedance. Well, it's quite possible that the tube in V2 may be Russian with a spiral filament in which case it's toast by now. I should check that...TOMORROW. I've done enough for one day!

I'm happy about where things are now. I didn't expect it to just run right as soon as I said it's done. But that it actually makes sound that's vaguely like the input signal, and that it has no shortage of LOUD, these are very encouraging things! 


Tomorrow I'll start taking notes on voltages all over the amp and recheck my work and be sure to verify component values. 

I'm fairly confident that there are no wiring errors. But that remains to be proven.

I did reuse some original "vintage" Cliff jacks for the inputs. Only input 2 works right now so I suspect I've got a bad jack. I have more. But I do want to use originals if they're still good. Just to show that I made an effort to retain some semblance of period correctness and originality in parts usage.


----------



## Matthews Guitars

I figured what the heck, I can mark out the voltages. This is where the voltages are as of now.


----------



## neikeel

@TAZIN that is the way my 68 was wired (with red waxed sleeving). 
The dpst ac switching is the better way to do it, same as simultaneous live/neutral on the mains as Chris will know. 
I guess it is how pure you want o be. 
Those voltages = amp with no load and outputs in.


----------



## Matthews Guitars

The amp was running with speaker connected and an input signal via signal generator at the time those voltages were measured. Volume turned all the way down.


----------



## Matthews Guitars

Incidentally in the process of comparing my '73 to this '69 to complete the wiring of the '69, I discovered something about my '73 that I'd missed when I rebuilt it, which was that it had an added flying resistor going to the cathode of V2. So rather than running an 820 ohm resistor to the cathode, it was actually running 2K. (The factory original resistor still on the board is a 1K maroon bodied piece. (Iskra or Piher? Which is red, again?) I gather that's a common deviation from the schematic, subbing the 1K for the 820.

The result is the amp was down on gain and I always have felt that it was a bit on the clean side, but it does early AC/DC tones very well. 

I removed the extra resistor and...daddy's HOME! It's definitely got more guts now, and sounds like I really had expected a Superlead to sound like. Very happy with that. With my drive pedal I can get a pretty good mild crunch before the volume is on 2. That may be a bit hotter than stock, but that'd be because I replaced V1A and V1B plate resistors with 150Ks a while back looking for a bit more push. I really like it just the way it is now, though, so I don't intend to revert that mod although I've saved the original resistors and they're safely taped to the inside of the chassis. 

As of this moment I've done nothing more to the '69 than to very carefully recheck the bias supply circuit and wiring. And I'm not seeing any problem in the wiring but I'm getting too much voltage. I've got 90 volts AC from the PT bias tap going into the 27K resistor and on to the reverse biased diode. After that point the voltage is 111 volts DC and varies hardly at all through the full travel of the 25K trim pot which is hooked up correctly as a rheostat. I've verified 25K worth of reistance value change across the circuit when running the pot across its full range.


----------



## Matthews Guitars

I solved the bias problem. Which was related to the fact that I am rebuilding an amp with limited documentation for the build procedures, and I stuck strictly with what I had for documentation. 

At no point in any photographs or diagrams that I am aware I have, was the bias circuit ground wire visible. 

So...it was an ungrounded bias circuit. I've since grounded it and now it's working properly. 

More testing to come right after I post this message....


----------



## TAZIN

Matthews Guitars said:


> Incidentally in the process of comparing my '73 to this '69 to complete the wiring of the '69, I discovered something about my '73 that I'd missed when I rebuilt it, which was that it had an added flying resistor going to the cathode of V2. So rather than running an 820 ohm resistor to the cathode, it was actually running 2K. (The factory original resistor still on the board is a 1K maroon bodied piece. (Iskra or Piher? Which is red, again?) I gather that's a common deviation from the schematic, subbing the 1K for the 820.
> 
> The result is the amp was down on gain and I always have felt that it was a bit on the clean side, but it does early AC/DC tones very well.
> 
> I removed the extra resistor and...daddy's HOME! It's definitely got more guts now, and sounds like I really had expected a Superlead to sound like. Very happy with that. With my drive pedal I can get a pretty good mild crunch before the volume is on 2. That may be a bit hotter than stock, but that'd be because I replaced V1A and V1B plate resistors with 150Ks a while back looking for a bit more push. I really like it just the way it is now, though, so I don't intend to revert that mod although I've saved the original resistors and they're safely taped to the inside of the chassis.
> 
> As of this moment I've done nothing more to the '69 than to very carefully recheck the bias supply circuit and wiring. And I'm not seeing any problem in the wiring but I'm getting too much voltage. I've got 90 volts AC from the PT bias tap going into the 27K resistor and on to the reverse biased diode. After that point the voltage is 111 volts DC and varies hardly at all through the full travel of the 25K trim pot which is hooked up correctly as a rheostat. I've verified 25K worth of reistance value change across the circuit when running the pot across its full range.



The V2a cathode resistor should be a 1K. The red colored resistors are Piher's.


----------



## TAZIN

Matthews Guitars said:


> I solved the bias problem. Which was related to the fact that I am rebuilding an amp with limited documentation for the build procedures, and I stuck strictly with what I had for documentation.
> 
> At no point in any photographs or diagrams that I am aware I have, was the bias circuit ground wire visible.
> 
> So...it was an ungrounded bias circuit. I've since grounded it and now it's working properly.
> 
> More testing to come right after I post this message....



This is why you should work with a schematic in conjunction with photos when rebuilding a specific era amp.
Now that the bias has been straightened out have the voltages throughout the amp changed?


----------



## Matthews Guitars

Yes, after I sorted out a connection issue with the choke as well! It's coming close to being a proper amp.

I was working off the schematic as well, to solve any questions that came up, but I just missed the bias ground entirely. 

I'm ALMOST there. I have to go out and get a 15K resistor (one value I'm out of) and then hopefully I can make it run right. 

My plan for this one is to run KT66 power tubes so I will probably have to juggle the value of the fixed resistor in series with the bias pot.

I have an original RS slider pot for true authenticity, one that's actually NOS in its original little carton, but when I saw what a cheap piece of junk it was, I decided to just go with a regular Stackpole 25K variable instead.


----------



## Matthews Guitars

I've got this amp mostly sorted out now but another bias related problem has come up. I'm not getting any current reading across the bias sense resistors on the power tube sockets, and I've got all resistors in the bias supply at spec values. The supply is properly grounded, supply voltage is in the right range and adjustable, but it's not actually biasing the tubes properly. Input voltage to the circuit is steady and indicating a reasonable current draw (based on the voltage drop under load) and the 47K bias resistor in series with the bias trim pot is showing up to a 42 volt drop across that resistor. Bias voltage range (not current, just voltage) ranges from about 36 to 55 volts as measured at the 220K resistors at the bias feed points. It's like the current capability of the bias supply is too low, yet the drive current to the circuit doesn't seem to be excessive based on the stability of the bias tap voltage off the PT. 


Running the bias adjustment trim pot across its full range does substantially affect the audio level of the output. So the bias, such as it is, is keeping the tubes very close to full cutoff. 

It's a weird puzzle that I look forward to solving.


----------



## Matthews Guitars

I'm trying to work out a discrepancy between the documentation I've found and how my other amps are built. Something's funky here.

Looking at my unmolested 2203 for reference, to try to understand what's the wiring issue I'm possibly facing, here's what I'm seeing:

Looking at the voltage divider ladder, the 8.2K feeding the 10K, at the top of it, it's fed by a blue wire from a capacitor which in turn comes from the fused HT voltage right off the rectifier. At the bottom of the lower resistor, the 10K, in the ladder, it's connected to...the power tube plates, one lead of the choke, and also off to one of the two series filter capacitor pairs.

The other end of the choke goes to a tie point that connects only to the white center tap of the output transformer, and the HV via the same HT fuse holder on the other lead. So this is fed from the HV thru the fuse.


Now looking at all the board documentation (photos) I've found so far, none of them show an isolated tie point for one wire of the choke, the center tap of the output transformer, and the HV. 

I'm interpreting what I'm seeing as, instead, those wires are also tied together with the blue wire at the top of the voltage divider. And I don't think that's right. I don't think that the HV, the plate supply, the top of the voltage divider ladder, the center tap of the OT, and one lead from the choke should all share one connection, not when it's not done like that in a similar Marshall. 

The thing is...there's not even an isolated eyelet on the 69's perf board in what I'd assume to be the right spot for that. There is an unused eyelet in the corner near the bias diode, but no photos I've seen have that eyelet used for that function.

I'm just trying to make sure that the amp is wired correctly to its original pattern. Which requires a little more information than I have.


----------



## Matthews Guitars

Adding further to the confusion, I'm finding different photos of different 1969 era boards showing different locations for the same wires. Such as the yellow plate voltage wire, or the red supply wire, which may be found on either the speaker jack side OR the controls side of the board. Color codes aren't consistent, either.


----------



## Guitar-Rocker

May I ask what you are calling the "plate supply" ? And the top of the voltage divider ( is that the B+ run towards the preamp) maybe should be on the down stream side of the choke?

I'm interpreting what I'm seeing as, instead, those wires are also tied together with the blue wire at the top of the voltage divider. And I don't think that's right. I don't think that the HV, the plate supply, the top of the voltage divider ladder, the center tap of the OT, and one lead from the choke should all share one connection, not when it's not done like that in a similar Marshall.


----------



## Matthews Guitars

Screen supply. I think I have it now. 


I'll try to explain. 

As I see it....and please confirm if I'm right, and correct me if I'm wrong...I've spent some time tracking this down and trying to match it up to both diagrams and schematics, and I THINK I have it now...

First, point of view is as seen with the amp controls in front closest to you.

Ignoring the filter capacitor that's hidden under the main board, the other five consist of capacitors for three functions.

The one under the fuses is for the pi filter and goes to the top of the 10K-8.2K totem pole next to the bias circuit. BLUE wire.

The two caps in series closest to the rectifier block is the main filter. It connects to the positive terminal of the rectifier block, thru the HT fuse. RED wire.
It is the main high voltage tap.

The two caps in series with the 56K dropping resistors on them are the screen filters. They connect to two points:
1: The bottom of the 10K-8.2K totem pole.
2: Direct to the screen resistors on pin 6 of the power tube sockets.
YELLOW wire.







The choke should connect to the bottom of the 10K-8.2K totem pole.

Now for the part I need confirmation of.

We have three wires to tie together now. I don't know where they were tied on the board originally but I can repurpose the spare lug in the
upper right hand of the board next to the bias diode.

Those three wires should be....as I see it...the other choke wire, the white center tap of the output transformer, and the mains supply via the tip connection of the HT fuseholder.
These three are not connected to any OTHER points. And this connection is where...I don't know where on the board it should be. Remember, I'm trying to put everything
where it would have originally been on this board.

Is this correct?


----------



## Trouble

yes, the 3 wires connect here on the corner turret. 

B+ fuse, choke, center tap


----------



## Matthews Guitars

Good deal. Thanks.


----------



## TAZIN

What wire is this (see Green arrow)? I hope it isn't one of the Choke wires?


----------



## Matthews Guitars

Yes that's a choke wire BUT it wasn't soldered there when the amp was running. That was when I was still figuring it out.

The last advice I got helped a lot. The amp is now working normally EXCEPT for a fairly loud hum that comes in as the tubes warm up, and is not affected by volume control settings. Pulling up the leads of the phase inverter coupling caps makes the hum reduce in volume but not go away comipletely. Pulling the cathode follower tube does not affect the hum. Pulling the phase inverter tube makes the amp silent.

The hum's sound is not affected by any control. 

I've been checking all my grounds and so far, nothing is standing out. Every ground on the schematic reads at zero ohms according to my meter, after checking my meter's own zero.


----------



## Trouble

Good catch,I didn't see that till you mentioned it.

I think this jumper may be feeding the wrong end.


----------



## Trouble

3 wires on top 

Choke, cap, and Pin 6 power tubes


----------



## Matthews Guitars

Here's the board as it is NOW. Working, but the amp hums. Loud enough that something is wrong. Hum does not change level in response to volume or tone control moviements.

Aside from the hum, the amp works properly, all inputs, and sounds right.

I am aware that one .68 uF mustard cap is not placed on the board. Reportedly, adding that cap eliminates the woody tonality that I'm after, so for now I'll leave it off in the absence of any compelling reason to add it. It's not the cause of the hum.


----------



## Matthews Guitars

Disconnecting the negative feedback wire (purple) from the impedance selector switch greatly reduces but does not entirely eliminate the hum.

Could the physical orientation of the output transformer (or power transformer, for that matter) cause hum? If I turn either around 180 degrees, might that help? (They are oriented normally as per the way other 1959s are made. I was very careful about that.)


----------



## Trouble

Still need to move the jumper


----------



## Trouble




----------



## Trouble




----------



## Trouble

see how the jumper goes to blue wire not 3 wire junction?


----------



## Matthews Guitars

Look at the photo on post 92 on page 5. It clearly shows the jumper going to the top (picture orientation top) of the bias, not to the top of the totem pole. (10K and 8.2K resistors)





This is THAT photo, from a working amp that isn't mine.

Your red board is apparently not identical in layout to my original '69 board. Its jumper configuration is different.

The schematic shows that there is a connection from the bias supply at the junction of the 18K and 47K resistors to the center feed point of the two 220K resistors. That matches this photo, and my current configuration on my board.

If I moved the jumper as you suggest. I'd be feeding part of the bias supply voltage to the plates of the phase inverter if I moved the other jumper off that connection. If I married the two, it'd blow up the bias supply with a hefty 300+ volts backfeeding to the bias supply from that plate supply. That would probably cost me a power transformer as I'm sure the 90 volt bias tap wouldn't react well to such abuse.

If the board isn't the SAME, the advice on making changes to it is probably not safe to follow.


----------



## Trouble

I was looking at the layout Neikeel posted in 113. That is also the way I have seen them. Which post is the schematic in?


----------



## Matthews Guitars

Marshall Unicord print dated 70-6-11, July 70. Readily found by Google search for "Marshall 1959 schematic". All other similar Marshall schematics show the same arrangement. That, of course, IS the bias feed to the power tubes.

The .pdf referenced by Neikeel and yourself on post 113 is not accurate to this board spec.


----------



## Matthews Guitars

I'm really hesitant to just start grounding stuff without being SURE it's the right thing to do, but at the moment, my speaker connections and output transformer output leads are all NOT grounded. They're floating. Shouldn't I be grounding one of these connections to the chassis?

That's another thing I've been unable to verify from photos. 

I spent a lot of money on that nice Merren OT. I don't want to ground it and kill it out of ignorance.


----------



## Matthews Guitars

Never mind...dupe post.


----------



## Matthews Guitars

If you look carefully, SOME of the '69 boards have the 2 resistor totem pole turned upside down in relation to mine. And that includes reversing the position of ALL the associated connections to the totem pole. This explains MOST of the differences between the diagram posted earlier and what's on my board and the reference board I posted. 

The diagram posted earlier more closely follows the OTHER layout with the inverted totem pole.


----------



## neikeel

If you leave that bus wire to the PI plates as it is you must move the other wires. The blue wire to the PI filter cap goes on the controls end of the 8k2/10k and the choke, screens wires the other end. At the moment your screens/pi are getting power feed/and power filtration in wrong order - hence the hum.


----------



## Trouble

As Neikeel said you can keep the jumper as is but you have to invert the wires at the end of the resistors. 

It sounds like you realized this in post 152.


----------



## TAZIN

Part of the problem is that your mixing two slightly different wiring styles ('69 & '70) which is causing confusion.


----------



## Seanxk




----------



## Matthews Guitars

That did it! It's running well. There is a little bit of unwanted distortion but I can trace that down.


----------



## Matthews Guitars

Almost there! I'm scoping the amp out and it seems to be doing fine. I'm picking up some stray electrical noise due to the lack of shielding, and I also need to go back and do a full wire dress job and make it neat which will help. 

Just one odd thing is happening: Despite my bias supply being steady, sometimes I'm not getting any reading across the 1 ohm resistors to ground on pins 1 and 8 on the power tube sockets. And other times I do. I should be reading 1 millivolt per milliamp. So, for 35 mA, I should be reading 35 mV. 

Sometimes I get that reading. Sometimes I get a reading of 0 mA but the amp is running OK. And when I get a reading of 0 mA, I'm STILL reading 45 or so volts on the bias resistors. It's like the resistors are turning into 0 ohm resistors at random. 

Yet...with no bias current drawn, the tubes should have bright red plates. But they aren't red plating at all and output appears normal.

Here's my voltage chart that's current as of now. The photo is out of date, I've swapped the screen feed since this photo was made, so keep it in mind. Line voltage was 120.0 volts.

See any serious issues? 

I'm seeing some WAY high voltages here. Need to figure that out.


----------



## neikeel

You are not dropping enough resistance after your screens
If you have 473v of HT on plates of output tubes then screens should be about 470v, then after the droppers I would expect 200v on the plates of your PI.
Your choke will have a DCR of 100ohms or so but the two resistors of =18k will drop things down but the output tubes drawing current should drop things more. The fact that you are only getting intermittent bias suggests that there is a problem with bias circuit. 
I run my output tube ground directly back to the output tube grounds (same place as the common wire of the OT (output jacks) is wired to.
I cannot see but I also wonder if the bias pot is wired correctly (two lugs need to be joined to make it a rheostat as opposed to a pot.


----------



## Matthews Guitars

Yes, the bias pot is wired as a rheostat. Wiper terminal shorted to one leg. 

The choke (which I believe to be original to this chassis) reads about 5 Henrys and I have another choke I could use which reads 8 Henrys. 

The bias voltage will appear on the red and green wires and on the 5.6K resistors going to each tube. Even when I can't read any bias current across the 1 ohm resistors, I still see the bias voltage at those points.


----------



## Matthews Guitars

I'm going to drop that 10K to 8.2K. Because I have it. That should lower the voltages somewhat.


----------



## Guitar-Rocker

If you drop the 10k to a 8.2k, the resistance is less and the voltage increases


----------



## Matthews Guitars

I realize that, and I expected it. I wanted to get a sense of how much a resistance change varies the voltage,
which will let me calculate current draw by the voltage drop as well.

There's something really funky going on with the bias. The circuit is working. It IS grounded. I can vary the voltage at the 5.6K resistors by a fair amount. (38 to 50 volts, roughly.) But the power tubes don't seem to be drawing any current. 

So, experimentally, changing the resistor values in the totem pole will change the screen grid voltage. We control bias via the control grid, but the screen grid plays a role as well. You can't ignore it. 

And I'm wondering if something about the screen grid voltage is keeping the tube from drawing bias current. I have a certain amount of audio power but without cranking the amp I'll never know how much. I do think that the tubes are only partially on. If I run the bias pot from one end of travel to another, I see a SMALL change in screen current, but it's a matter of just about 2 MV. However this does change the level of any residual hum.

If the tubes are barely conducting, it stands to reason that the voltage dividers won't work correctly. They need a load in order to start seeing any real voltage drops.


----------



## Matthews Guitars

....and it helps to connect the plate supply voltage for the phase inverter to the correct spot! I ended up having to move that jumper anyway, which I had hoped to avoid doing. Now instead of an X on those jumpers, they're two parallel diagonals. I had to move it from the bottom to the top of the totem pole. 

That solved my voltage issues. Now all the voltages are right where they're supposed to be according to the schematic. 

But the bias system still isn't working right. I can control the bias voltage but the read bias current is still down between 0 and 2 mA.


----------



## Trouble

Matthews Guitars said:


> The circuit is working. It IS grounded. I can vary the voltage at the 5.6K resistors by a fair amount. (38 to 50 volts, roughly.) .


 -38 to -50?


----------



## Matthews Guitars

Eventually I figured it out. I've got everything working properly now. 

It was all related to that mess around the PI cap, the screen cap, and the associated wiring. At one point I had the screen tied to the low voltage side of the totem pole so it was running at 330 volts with a 470 volt plate. Moving that screen feed to the high side of the totem pole solved THAT. And making sure that the phase inverter plates are fed from the low voltage side of the totem pole was equally important. 

Now for the wire dressing and cleanup. And I'm going to redo the filament string because it's kind of sloppy. I can do better. 

I turned the PT around late last night so the wires all come out of the holes they're supposed to. I hadn't realized until yesterday that it was installed 180 degrees off. It'll be a clean wiring job after I've got everything trimmed and dressed.


----------



## Matthews Guitars

I have to say, I've learned a LOT from this rebuild. When I rebuilt the '73 Superlead, it went together very smoothly as it didn't vary from readily available documents at all, being an early ST1 board type. As a result, I didn't really learn all that much about how the amp really works. 

But this one was super educational.

I now can point to any component in the amp and know what it is, where it is in the schematic, and its function. That doesn't mean I know every little nuance of it, but at least there are no BIG mysteries.

I've ordered up a new '69 spec headshell for it from Sourmash. And I'm now working on getting my first batch of real plexi reproduction panels made. (Actually they're lexan polycarbonate, which is stronger.) 

I plan to play it for a while and explore its tonal range thoroughly before I do any mods to it and put that extra tube socket to work.


----------



## Matthews Guitars

It's done. Leads trimmed and dressed, tested and played up to and including full volume. Sound is similar enough to my '73 that I don't think there are any significant bugs in it.

The channel 1 volume doesn't go down quite to zero. Not sure if that's due to the volume pot or not. But it still gets quiet enough that it's not an issue under any conceivable circumstances.


----------



## Matthews Guitars

I meant to ask this some time ago. But forgot. 

Being as this is a '69 Superlead, equipped with a grommeted power cord and no mains voltage selector, what power tube type would it have most likely been equipped with originally? KT-66 or EL-34? 

My supply voltage is right around 470 volts with 120 volts AC input power. All voltages are well within specifications as per the print.


----------



## Matthews Guitars

I need another old ratted out Marshall to restore! Someone find me one! The rattier, the better!


----------



## Matthews Guitars

The photos:


----------



## neikeel

Matthews Guitars said:


> what power tube type would it have most likely been equipped with originally? KT-66 or EL-34? .




For 50 and 100w
El34 were stock, typically Mullards
KT66 stopped early 67
6550 late 70s early 80s in USA - better confirm that last bit!


----------



## Matthews Guitars

A hint of what's to come....I'm starting to make plexi replica panels now to complement my metalface panels. 

My samples were cut with incorrect hole sizes but that doesn't keep me from testing the gold paint and the printing. 

Yes, this is the wrong font. I know. But I'm just doing tests for now. I do have the right font, and since everything else is going according to plan, I'm starting plexi panel production in a week or two at most. 

I'm using Lexan polycarbonate. Which is several times stronger than plexiglas.


----------



## Matthews Guitars

Quick question.

The .68 Mustard cap bypassing the 820 ohm resistor on V2....some amps have it, some don't.

Tonally speaking, what's the difference? 

Should this '69 lead spec amp have that cap or not?


----------



## neikeel

Matthews Guitars said:


> Quick question.
> 
> The .68 Mustard cap bypassing the 820 ohm resistor on V2....some amps have it, some don't.
> 
> Tonally speaking, what's the difference?
> 
> Should this '69 lead spec amp have that cap or not?



Probably yes with an 820R cathode resistor and 47k/8ohm NFB

Later amps used 1k cathode resistor but no cap and 100k/4ohm NFB


----------



## Matthews Guitars

Tonally speaking, how is it going to alter the sound or response of the amp?

I'm also seeing that SOME amps stack a 10K resistor and an 8.2K resistor in the totem pole, while others stack two 8.2Ks. I'm not sure which is more
correct for this amp, either. I am getting 468 volts at the plates and the KT66s are biased to 70 percent value. Whatever that is. I confess I don't remember exactly
but I think it was 32 mA per tube.

The tonal goal is, basically, "vintage brown", a true Plexi tonality.


----------



## stickyfinger

Curious as what mA you measure on the coupling caps for V1 an tonestack.


----------



## Matthews Guitars

Next time I have the chassis out of the box I'll take measurements. 

The current box is unshielded. I've got a new one coming from Sourmash for it. That one's shielded and I'm hoping that'll cut down on the residual noise. There is some white noise present even with the volumes all the way off. It's very low in level but it's there. It is most affected by the positions of Volume I and Volume II. And a little bit of 60/120 Hz hum is present as well. I may have to check some coupling caps for leakage. Volume II (bright channel)'s volume pot is a bit scratch though all pots are brand new. Maybe there's a little DC on there due to a leaky coupling cap. All things to check next time I've got it on the bench.


----------



## neikeel

Matthews Guitars said:


> Tonally speaking, how is it going to alter the sound or response of the amp?[?quote]
> 
> Upper mid boost (people have used a bigger cap like 300uF electro but IMO gives you mush, Friedman uses a 680nF and a largish electro in parallel there and if you had a hack amp to play with you could put in a 3 way switch, none, 680nF and say 100uF options.
> 
> 
> 
> Matthews Guitars said:
> 
> 
> 
> I'm also seeing that SOME amps stack a 10K resistor and an 8.2K resistor in the totem pole, while others stack two 8.2Ks. I'm not sure which is more
> correct for this amp, either.
> 
> 
> 
> The higher the value of those two resistors the lower the voltages downstream from PI to preamp, the 10k/8k2 is commonly used on amps with 490 on octal anodes. 8k2/8k2 is a 50w value with 420v on octal anodes. Depends on how brown you want your preamp. Bigger resistors= lower preamp voltage = less headroom and vice versa but at these values the differences are pretty minor.
> 
> 
> 
> Matthews Guitars said:
> 
> 
> 
> I am getting 468 volts at the plates and the KT66s are biased to 70 percent value. Whatever that is. I confess I don't remember exactly, but I think it was 32 mA per tube.
> The tonal goal is, basically, "vintage brown", a true Plexi tonality.
> 
> Click to expand...
Click to expand...


----------



## stickyfinger

Scratchy pots indicate DC likely. Unlikely that the Mustards are bad unless you damaged them soldering. I've used well over 100 NOS Mustards and never had a leaky cap.
If you have mA on the Mustards you need to pull the lead and measure the actual turret for a leaky board as was my thought behind my first question.


----------



## Matthews Guitars

I finally found these photos. This is of the '69 chassis after getting all the extra and damaged holes welded up.


----------

