Starting a 2204 Build

[BenTobith]

Looking great so far! I am contemplating building one of these if I can make it out alive from my upcoming Hiwatt build.

Does anyone know if you can do a 2204 inside of a 24" wide Marshall head cabinet? Wasn't sure if they'd fit in those smaller box head cabinets, or if they require the 29" wide ones?

 

[ledvedder]

For the life of me, I can't figure this thing out. Maybe I bit off more than I could chew. I tried to do this "Neil Special" 2in1 1987/1959. All I'm getting in 2 of the inputs is a hum that gets louder as I increase the MV. In the channel II low input, I get some sound, but it's barely there with the hum.

 

[playloud]

For the life of me, I can't figure this thing out. Maybe I bit off more than I could chew. I tried to do this "Neil Special" 2in1 1987/1959. All I'm getting in 2 of the inputs is a hum that gets louder as I increase the MV. In the channel II low input, I get some sound, but it's barely there with the hum.

Have you checked your input resistances? Could be dumping audio to ground due to incorrect wiring. https://robrobinette.com/Tube_Guitar_Amp_Troubleshooting.htm#No_Guitar_Audio

After checking that, I would skip to this: https://robrobinette.com/Tube_Guitar_Amp_Troubleshooting.htm#Bad_Guitar_Audio

 

[neikeel]

Let's go through this, the wiring should be pretty clear.
Do you have the jacks grounded properly and of the correct (original spec) shorting variety?
With nothing plugged in and volumes down what do you get?
Decent detailed pics and we will get you there (if I have to pull one open and take pics (mine is the normal lead dress tho')

 

[ledvedder]

Let's go through this, the wiring should be pretty clear.
Do you have the jacks grounded properly and of the correct (original spec) shorting variety?
With nothing plugged in and volumes down what do you get?
Decent detailed pics and we will get you there (if I have to pull one open and take pics (mine is the normal lead dress tho')

With nothing plugged in and volumes down, there is no noise. When raising the MV, it's starts to hum and hiss. The hiss noise does change with the tone controls and preamp gain. I've pulled the the input jacks and preamp gain pot once and went over the wiring with a fine tooth comb. Didn't see any issues. Maybe I'll try it once more before I give up and go with a straight up 2204.

I also start to get high pitched oscillation as I turn the gain pot up.

Another thing happened last night. Now I'm not sure if this is normal, since I haven't done it before. I hadn't screwed the turret board in yet. So when I was prodding around with a chopstick, the board moved, which made a loud pop through the speakers. I then started lifting the board a bit and was able to make that sound happen over and over. Maybe there's an issue under the board.

 

[dslman]

Hope you get it figured out, it looks amazing! My 2204 build had volume drop, and loud bumping noise through the speakers, after initial build too. My builder went through it several times , rechecking wiring, and re flowing solder . I think it was a combination of a loose power tube socket that would move, and a bad preamp tube, he wasn't sure the reflowing, and checking helped or not. It was a pain, but he got it solid. I'm sure you will also.

 

[ledvedder]

Sorry, bad post

 

[neikeel]

Common issue can be trapping a wire between stand off and board can cause a short. `Other thing is that moving the board around reveals a dry joint.

Please put some pics up of what you have.

 

[ledvedder]

Common issue can be trapping a wire between stand off and board can cause a short. `Other thing is that moving the board around reveals a dry joint.

Please put some pics up of what you have.

Let me know if this link works.

2204/1987 build issues

11 new items added to shared album

photos.app.goo.gl

 

[neikeel]

You’ve done something funky with your input jacks. The 1M goes on the hi input jack. So I suspect you have wired the jacks upside down and dumping signal to ground.
Some of the solder joints could be better - I found those turrets needed a lot of heat to flow. Maybe dab of flux to help?

 

[ledvedder]

You’ve done something funky with your input jacks. The 1M goes on the hi input jack. So I suspect you have wired the jacks upside down and dumping signal to ground.
Some of the solder joints could be better - I found those turrets needed a lot of heat to flow. Maybe dab of flux to help?

Yeah, I'm definitely gonna go through all the joints and reflow. Input jacks always get me! I'll have to pull them out and redo them.

 

[neikeel]

This is an old pair of jacks, you have to make sure that it is this way up because of the way the switching contacts work
Green wires are grid wires to board
Black wire is to the ground point.
The resistor goes closest to the top of the chassis (ie high input)

 

[ledvedder]

I think I got it all sorted out. I re-did the ground connection at the 50/50 preamp cap, since it also provides ground for most of the preamp. I also reflowed several other joints that didn't look good. Everything seems to be good now. Thanks everyone for helping me get through this. Now it's time to start thinking about how to mod this thing. #34? JEL? Hmmm...

 

[ledvedder]

I may have spoken too soon. I was trying some bypass caps across the 10k cathode resistor, and noticed that buzz again. It almost goes away if I just clip an empty alligator clip on it. I've reflowed the joints on both sides, but it's still like this.

 

[neikeel]

Are you clipping the wire to ground or just putting clip on it? If ground I’d check the shared ground connection on the cathode of v1.
If just a wire it suggests RF. Does putting your hand over that area affect noise. Do you have fluorescent tube lighting in your work area?
Again check the grounds.
I’ve tried #34, #36 mods and find them unbearably bright and always want a switching out option and it sounds like you are not quite ready for that yet.

 

[Pete Farrington]

Valve guitar amps tend to oscillate. It’s just their thing, especially if mods for gain / treble boosting are in play.
You have to get busy with a scope, deduce what’s in the loop and from that, devise suitable mitigation.

 

[South Park]

if you get a pop sound when you chop stick the amp board you have a bad connection , check for ground loops in the input and gain stage pot . nice job

 

[ledvedder]

You’ve done something funky with your input jacks. The 1M goes on the hi input jack. So I suspect you have wired the jacks upside down and dumping signal to ground.
Some of the solder joints could be better - I found those turrets needed a lot of heat to flow. Maybe dab of flux to help?

Now that I have all the issues sorted out with the straight up 2204, I think I'm gonna give the 2in1 another shot. I tried converting the cathode follower to a 4th gain stage, but it's just way too much gain for me. So I converted it back to 2204. Any tweaks you'd recommend for the 2in1? Or is it the same as you've drawn it up?

 

[neikeel]

Just as I’ve drawn it. I like the tone of 1987 lead to 68 spec ( hence the 0.68 over 820r on V2a and 47k/8ohm NFB.
Using 8k2 on the cold clipper cathode is slightly more gain than stock but retains that 2204 kerrang.

 

[ledvedder]

Just as I’ve drawn it. I like the tone of 1987 lead to 68 spec ( hence the 0.68 over 820r on V2a and 47k/8ohm NFB.
Using 8k2 on the cold clipper cathode is slightly more gain than stock but retains that 2204 kerrang.

Do you know if it's possible to make it footswitchable?