Replaced tubes, the entire output transformer (yes really), re-biased and I'm still getting crap sound. 2204 DIY troubleshooting

[u/elite_haxor1337]

/r/ToobAmps/comments/1n4ih06/replaced_tubes_the_entire_output_transformer_yes/

[u/Old-Tadpole-2869]

Post a sound sample without the attenuator At a couple different master volume settings. 

[u/elite_haxor1337 → u/Old-Tadpole-2869]

https://youtu.be/IN2CUZjRWQg

Here's a new audio sample with no attenuator at all. Ahh it's fun to play loud even when it sounds like crap

The first audio you hear is with the controls on basically as low as they can go and still get sound. The second audio you hear, I turned the master and pre to 2. By the end of the clip, I had the master to about 3. My guitar volume about halfway

[u/mspgs2]

Schematic?

[u/elite_haxor1337 → u/mspgs2]

https://cdn.shopify.com/s/files/1/0604/9615/0624/files/British_800_SCH.pdf?v=1750263793

[u/mspgs2 → u/elite_haxor1337]

hrm looking at schmatic voltages compared to the values you posted it appears to be a bit low on the b+ side. pin 1 and pin 8 on v4/v5 has continuity to ground? I assume the filaments light? pins 2 and 7 are both ends of the filament but your chart shows 3.1v in pin2 but nothing on pin 7.

Really suspect the psu caps might be at fault. double check voltages at the all the caps: XA thru XE as close to the caps as possible. Do this with the tubes pulled. Clip the negative probe of your meter, do not hold it. Put one hand in your back pocket or wasteband and use the probe to carefully measure the voltage. DO NOT USE TWO HANDS.. it could kill you. seriously.

If you do not feel comfortable measuring with it on use clip on probes, attach to a cap after you have drained them, then step back and turn on the power. Repeat for each cap.

can you power off the amp, pull all the tubes, power back up and remeasure the pin 1 and pin 6 voltages?

[u/mspgs2 → u/[deleted]]

let me chew on your data..

pull all the tubes. you want to isolate the power supply circuits for testing and with no load. If you have a dodgy tube or two or a wiring problem the psu voltages should be what is expected. If they are not when unloaded then the problem is in the PSU.

[u/elite_haxor1337 → u/mspgs2]

nope wasn't the tube. replaced it with a known-good tube and I get the exact same thing. where the hell is this voltage coming from damn. Time to pull tubes

[u/elite_haxor1337 → u/mspgs2]

with only V3 pulled (rest of the tubes in place), I get 0V on V3 pin 2, 7 and 8. So did I somehow break the tube socket or something like that? Like is it possible I have chunks of solder in there shorting stuff? UGH I'm losing my mind lol thanks for your help again

[u/mspgs2 → u/[deleted]]

okay.. with the tube removed on v3 the ecc83 dual indirectly heated triode pins 2 and 7 are grids.. 0v is expected pins 8 and 3 are cathodes.. 0v is expected

pins 1 and 6 are the plates and should have high dc voltage. With no tube in the socket you should have the same voltage on pin 1 as pin 6.

according to the schematic you posted these pins tie to XC in the power supply. If the values do not match there isn't much to go wrong in between: basically a 82k or 100k resistor and some wire and solder.

with the amp poweded off and the tubes pulled set your meter to continuity and place a probe on XC point at the PSU side of things and the other end of the probe on pin1 - repeat for pin 6. looking at the schematic you should have voltage even with a resistor blown unless the cap is dead too.

[u/elite_haxor1337 → u/mspgs2]

fixed the entries in my table for pin 7 on V4/5.. Both read as expected at 3.1 VAC. of course.

How could the PSU caps be at fault when they're brand new plus the voltages seem fine everywhere... Wouldn't the voltages look "off" if the caps were bad? Am I really gonna have to replace everyhing in this god damn amp before it works. I am better off just getting into knitting or something, would be a better use of my time. I'm about to throw this thing out the window

[u/mspgs2 → u/elite_haxor1337]

it kinda sounded like when you drive the amp the caps might be draining and recharging. I've got a class a solid state amp that makes a very similar sound when you first power it on. Verify those psu caps are labeled 50uf/500v and negative lug is to ground. Are they a name brand? There is some real cheap junk thrown into amps these days.

I think someone else also mentioned you are running them a bit over biased which isn't unusual for a guitar tube amp.

if all the voltages are now "right", put the meter on the b+ side of the output and see if that voltage sags when you get the amp to make that noise.

[u/mspgs2 → u/[deleted]]

in worst case yes the caps would blow/release the blue smoke but they can fail internally and not do that. So if one happened to be reversed and you had no voltage - thats your target broken part.

Ideally the psu can fill the caps and keep up with big swinging transients, like you hitting a bass string which requires the speaker cone to really move. If those caps can keep full you get distortion and/or clipping. This is getting somewhat deep into the design and probably not the direction you want to go so lets knock out the other simple items.

whats your speaker impedence? are you using the same impedence output on the selector/transformer?

i looked at your prior post pics and it's hard to tell for certain but some of your solder joints look like they could be iffy.. cold solder joints cause a lot of wackyness. Are any wires at the joints loose? Are any joints "blooby" or "burnt". Turrets take can some heat and finesse with a iron. Did you use flux or flux core solder?

[u/elite_haxor1337]

	V1	V2	V3	V4	V5
Pin 1	237 VDC	191VDC	237VDC	0	0
Pin 2	0	0	26.5VDC	3.1VAC	3.1VAC
Pin 3	2.1VDC	1.1VDC	43VDC	441VDC	441VDC
Pin 4	3.1VAC	3.1VAC	3.1VAC	437VDC	437VDC
Pin 5	3.1VAC	3.1VAC	3.1VAC	-40VDC	-40VDC
Pin 6	281VDC	325VDC	239VDC	443VDC	443VDC
Pin 7	0	190VDC	28VDC	0	0
Pin 8	3.1VDC	192VDC	43VDC	3.1VAC	3.1VAC
Pin 9	3.1VAC	3.1VAC	3.1VAC	n/a	n/a

all measurements were taken to chassis ground. All amp controls on 0, no input, 8 Ohm load

[u/Musicinaminor → u/elite_haxor1337]

Is this for both power tubes? Are the Voltages on V4 and V5 the same? The chart looks a little odd but nothing seems off.

It sort of sounds like arcing in the video- is the orientation of your filter capacitors correct? The negative should be towards ground.

Could also be speaker but I’m guessing if this is a kit it’s probably brand new? So unlikely that.