Need 5E3 Build Troubleshooting Help

Matthews Guitars

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I think you need to gain a better understanding of resistors in circuits.

The voltage drop across the resistor is very important. It tells you what's going on.

If it's grounded on one end, then it will read supply voltage on the supply side and zero volts on the grounded end.
It should not read zero volts on that end if it's not supposed to be at a ground point. If it is, what follows it is a hard short to ground.

You've got a 4.7K resistor that baked due to a shorted tube and it was telling you, very clearly, "The circuit is drawing too much current through me!" It's basically pointing right at the problem. It'll almost always be the device being fed by that resistor, which can draw current.

You need to know how to calculate whether or not a resistor is big enough to handle the current it's going to experience in circuit.



Learning electronics makes troubleshooting infinitely easier when you have a problem with your build.
 

Pete Farrington

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I will redo all the grounding, I just need a plan which I havent found yet.
If there’s no hum there’s no real benefit from that.
It’s only the method by which the chassis gets its safety earth connection that’s being referred to.
ie use a dedicated screw, locking nut and star washer for the lug from the earth wire of the mains cable.
 
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paul-e-mann

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If there’s no hum there’s no real benefit from that.
It’s only the method by which the chassis gets its safety earth connection that’s being referred to.
ie use a dedicated screw, locking nut and star washer for the lug from the earth wire of the mains cable.
I'll do that. The amp is dead quiet.
 

Im247frogs

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This is mine, with a BareKnuckle VHII bridge humbucker in an alder Tele, with the channels jumpered, Master Volume all the way up, bth volumes about 2/3rds up. Mighty crunchy. Granted, I cant really get this with my Strat w noiseless single coils. It does have the lead channel mod, but it still breaks up nicely without it. The marshall preamp values add a much smoother breakup which mixes well w the regular channel. I really may go back to stock, its fatter, warmer, and has much more pick sensitivity.

 

playloud

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This is mine, with a BareKnuckle VHII bridge humbucker in an alder Tele, with the channels jumpered, Master Volume all the way up, bth volumes about 2/3rds up. Mighty crunchy. Granted, I cant really get this with my Strat w noiseless single coils. It does have the lead channel mod, but it still breaks up nicely without it. The marshall preamp values add a much smoother breakup which mixes well w the regular channel. I really may go back to stock, its fatter, warmer, and has much more pick sensitivity.



That sounds cool, and probably makes a good case for the mod - it wouldn't be holding up so well with this much gain otherwise. Otoh, I can see the case for reversing the mods and giving it less input. That edge-of-breakup 5E3 thing is really nice.

What kit?

A bit of a hybrid.

I started with one of these kits, and also ordered a couple of black OC44s that I found on Ebay. I chose the one with the best h_FE (~97 from memory) and ended up replacing the polystyrene input/output coupling caps with modern mica ones from my local electronics shop. I experimented a little with the input value, but settled on the stock value (or modern equivalent, i.e. 4.7nF). I also replaced the 68k resistor with a 200k trim pot in order to bias the transistor.

I also wired this all up in a standard Hammond 1590 enclosure (it was a tight fit!) with a 3PDT footswitch and LED in true bypass.

This article is really excellent: https://www.electrosmash.com/dallas-rangemaster

It's a simple circuit, so easy to 'tune' to your taste. If you have recording software, it's also quite satisfying to record it and inspect the assymetrical waveforms directly (a "poor man's scope" if you will!)
 

paul-e-mann

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This is mine, with a BareKnuckle VHII bridge humbucker in an alder Tele, with the channels jumpered, Master Volume all the way up, bth volumes about 2/3rds up. Mighty crunchy. Granted, I cant really get this with my Strat w noiseless single coils. It does have the lead channel mod, but it still breaks up nicely without it. The marshall preamp values add a much smoother breakup which mixes well w the regular channel. I really may go back to stock, its fatter, warmer, and has much more pick sensitivity.


Does it take OD pedals well? I tend to run amps at edge of breakup and boost with OD. Right now mine without a MV I cant use OD pedals.
 

Im247frogs

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Does it take OD pedals well? I tend to run amps at edge of breakup and boost with OD. Right now mine without a MV I cant use OD peda
Not so much. a boost like an Xotic EP can be helpful, but an actual distortion pedal, it can get ugly pretty fast. The master volume control is pretty essential if you can't crank it to breakup levels, which isn't too loud, but too loud for my apartment building.
The tone control also seems to add a significant amount of gain so it's worth fiddling with.
 

paul-e-mann

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Not so much. a boost like an Xotic EP can be helpful, but an actual distortion pedal, it can get ugly pretty fast. The master volume control is pretty essential if you can't crank it to breakup levels, which isn't too loud, but too loud for my apartment building.
The tone control also seems to add a significant amount of gain so it's worth fiddling with.
Maybe with the MV I'll be able to get enough crunch out of it and I wont need pedals at all, I'm always going for ACDC Zep tones which are fairly low gain.

Robinette says the "Lead Channel" mod makes the amp more Marshally and makes it more pedal friendly, do you find this true or no?
 

Im247frogs

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What Rob means (I would imagine) is that’s it’s more pedal friendly compared to the normal circuit of a 5e3.

The stock circuit is prone to bad-sounding “farty” distortion when pushed hard with hi output humbuckers or dirt pedals.

The Marshall style preamp tightens up the low end frequencies and pushes the signal into clipping distortion much more smoothly and can take a bigger signal without farting out.

The rationale behind modding one of the channels is that the bright and normal channel are exactly the same except for the bright channel bright capacitor and tone control, so why not mod one channel? Once you do that, though, it’s a totally different amplifier and you lose a lot of the unique features that make it a 5e3 in the first place.

I did the lead channel mod for the hell of it, and it’s very cool BUT I’m probably going to put it back to stock in the very near future because I have 4 or 5 Marshall or Marshall style builds and if i want that sound I have it. The 5e3 as it is doesn’t sound like any amp I’ve ever owned.
And I can use my a/b/y pedal to plug into it and any one of my other amps:hbang::hbang:
 

paul-e-mann

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What Rob means (I would imagine) is that’s it’s more pedal friendly compared to the normal circuit of a 5e3.

The stock circuit is prone to bad-sounding “farty” distortion when pushed hard with hi output humbuckers or dirt pedals.

The Marshall style preamp tightens up the low end frequencies and pushes the signal into clipping distortion much more smoothly and can take a bigger signal without farting out.

The rationale behind modding one of the channels is that the bright and normal channel are exactly the same except for the bright channel bright capacitor and tone control, so why not mod one channel? Once you do that, though, it’s a totally different amplifier and you lose a lot of the unique features that make it a 5e3 in the first place.

I did the lead channel mod for the hell of it, and it’s very cool BUT I’m probably going to put it back to stock in the very near future because I have 4 or 5 Marshall or Marshall style builds and if i want that sound I have it. The 5e3 as it is doesn’t sound like any amp I’ve ever owned.
And I can use my a/b/y pedal to plug into it and any one of my other amps:hbang::hbang:
I like your aby pedal idea, im gonna have to get me one! :yesway:
 

paul-e-mann

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Every speaker I put in this thing sounds super good, I just got the Jensen C12Q in the mail and its a keeper! Tried a Wharfdale GHS-1230 it sounded great too, creamback 65 and 75 sounded great, greenback great! :yesway:

I carved up an old speaker cab and turned it into a combo cab and its working out well. I'm just waiting on the shielded wire I need to install the PPIMV, slow pokes its gonna take a week to get to me. Meanwhile I'll enjoy the punchy cleans I get out of this thing, it doesnt break up at all at reasonable volume, cranked up to 8 I'm on the verge of break up but its loud but sounds good like early Who, I have plenty more to dial once I get that PPIMV and jumper the channels it will get even louder! :yesway:
 
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paul-e-mann

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I got the PPIMV installed, got rid of the standby and put it in that hole, sounds really good I can get some low crunch at reasonable volume, and it takes boost pedals well, very happy with it. Robinette mentions adding an optional bright cap to the pot but doesnt say what value. I'd like to brighten the tone a bit what bright cap should I use?

mxPEwyc.jpg
 
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Im247frogs

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Bright cap where? Like the Vox cut control?
You should shove a patch cord in from bright 2 to normal 1 for interesting fatness.
Also I was going to ask if you've tried a 12ax7 in V1 instead of the normal spec'd 12aY7 so you get more gain/crunch.

*edit* If you're talking about the vox MV w cut control, that is a Post phase inverter MV mod. Is that what you installed? I did the Pre-PI mv on my 5E3.
 
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paul-e-mann

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Bright cap where? Like the Vox cut control?
You should shove a patch cord in from bright 2 to normal 1 for interesting fatness.
Also I was going to ask if you've tried a 12ax7 in V1 instead of the normal spec'd 12aY7 so you get more gain/crunch.

*edit* If you're talking about the vox MV w cut control, that is a Post phase inverter MV mod. Is that what you installed? I did the Pre-PI mv on my 5E3.
Its a pre pi master. I have 12ax7 in it. Robinette's pre pi master plan mentions optional bright cap but mentions no detail of what and where.
 

paul-e-mann

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Bright caps are connected between the input and output terminals of a pot, hot track end and wiper.
I suggest starting with 100pF, get a couple of values either side, in case you want more or less of an effect.
See the layout below, I assume the .0047uF cap on the tone pot is the bright cap, are you suggesting I replace that cap with 100pF? Is Robinette suggesting I put a bright cap on the master volume pot (master is where the standby used to be)? Currently I have the amp tone turned all the way up for humbuckers and about half way for single coils, I wouldnt mind being able to go a little bit further for humbuckers. You suggest I get a couple values to try, can you tell me what to get and where exactly they go, if you can walk me through this I'm not good with the lingo and what parts are called. Thanks Pete!

J1BEKdZ.jpg
 


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