Super High voltage AB763 Super Reverb

[Beardsley]

Hi
This is my first post, but I've been hiding in the shadows. This is a great forum!
So... Ive put together this AB763 Super Reverb clone that I got from [deleted at OP's request], basically a Mojo kit. Very good quality. Fired her up, and there is sound, but very low, like that of an altoids can amp. Also very distorted.
Ive checked and rechecked all of my connections and everything seems in order, but some of the voltages are very high!
The 4th preamp tube from the right (v2b? maybe?) has 358v on pins 1 & 6 where fenders layout shows 270v.
Then the 5th tube, 12ax7, has 459v on pin1, 0v on pin3, and 408 on pin6. They show 280v, 2.5v, and 280v respectively.
The next 12at7 has very similar readings at pin1 is 453v, 15v on pin3, and 450 on pin 6. Fender shows 230 on 1, 106 on 3, and 230 on 6.
All the rest of the voltages seem fine including the cap board. I just cant seem to find the problem. Im hoping someone recognizes something here and sorry for the extended post. Thanks for all the useful info obtained by flipping through this forum, and thanks in advance for anyone with any feedback.
Red

[Bruce / Mission Amps]

Check the actual ground connection of the cathode biasing resistors in those preamp tubes with high voltage on the anodes.\
Sounds like they are not really turned on.

[axpro]

It does sound like you are missing a ground. turn the amp off, and use your meter to check continuity from true ground, to everything that is supposed to be ground on the board. I had a similar problem with my current build, it ended up being a disconnected ground wire on theb ottom of the eyelet board. DOH!

[Beardsley]

checked all f the grounds, as well as all of the under board connections with the continuity tester. Everything seems correct. Could a bad tube have this effect on the voltage?

[MWJB]

Double check the value of your plate resistors (pins 1 & 6 @ 100K, 82K etc). Check the value of the power supply resistors in the cap pan too (1K & 4.7K). Check value of cathode resistors (pins 3 & 8).

Also to be sure that we are talking about the same tubes, count from right to left, from the back of the amp, V7 & V8 will be the power tubes, V1 is nearest the normal channel inputs, etc.

list voltages at ALL tubes 1-6 at plates & cathodes (pins 1 & 6, 3 & 8) & for power tubes at pins 3, 4, 5 & 6. Your plate voltages might be high, but knowing the cathode voltages will tell us how much current the tubes are drawing & might point to some clues?

[Beardsley]

ok here goes:

v1
pin1 277v pin3 2v
v2
pin1 259v pin3 253v
v3
pin1 462v pin3 8v
v4
pin1 358v pin3 3v
v5
pin1 459v pin3 0v
v6
pin1 453v pin3 15v
v7
pin3 465v pin4 466v pin5 -51v pin6 468v
v8
pin3 468v pin4 466v pin5 -51v pin6 468v
also, I just noticed that I have a 470k in the phase inverter instead of 470ohm but thats all I got with the kit. Would this change the voltages thi dramatically?
Thanks
Here are some really bad pics for those of you that drink alot and are used to blurred vision....

[Bruce / Mission Amps]

ok here goes:

v1
pin1 277v pin3 2v
v2
pin1 259v pin3 253v
v3
pin1 462v pin3 8v
v4
pin1 358v pin3 3v
v5
pin1 459v pin3 0v
v6
pin1 453v pin3 15v
v7
pin3 465v pin4 466v pin5 -51v pin6 468v
v8
pin3 468v pin4 466v pin5 -51v pin6 468v
also, I just noticed that I have a 470k in the phase inverter instead of 470ohm but thats all I got with the kit. Would this change the voltages thi dramatically?
Thanks
Here are some really bad pics for those of you that drink alot and are used to blurred vision....

Yikes, fix the 470 ohm resistor first and then let's start over... I guess you should check to make sure there are no other issues like that.

[txstrat]

Here are some really bad pics for those of you that drink alot and are used to blurred vision....

Well, getting older than 46 and forgetting your spectacles is enough to get used to blurred vision.
At least in my case.

[axpro]

Yikes, fix the 470 ohm resistor first and then let's start over... I guess you should check to make sure there are no other issues like that.

rofl!

I've had that happen a few times, but unlike the OP, I can't blame it on a kit, since i picked the parts myself! (not reading values correctly when assembling!)

[Beardsley]

Thanks for all the responses! Fixed the 470. It fixed only a few voltages. Many are still high. Checked everything else and it seems ok (of course Im no expert at color codes) So here are the new values:
v1 7025
pin1/275 pin3/2.3 pin6/285 pin8/2.3
v2 7025
pin1/256 pin3/2.4 pin6/250 pin8/2.3 pin1 should be 270, but its pretty close although its low instead of high like the others.
v3 12AT7
pin1/462 pin3/8.6 pin6/462 pin8/8.6 these are fine. Should be 450 and 8.4
v4 7025
pin1/353 3/3.5 6/354 8/3.5 pin1 should be 270.
v5 12AX
pin1/455 3/0 6/404 8/0 pin1 should be280, and pin3 should be 2.5 but there is no voltage.
v6 12AT7
pin1/249 3/107 6/241 8/107 pretty close
v7 6L6GC
pin4/465 5/464 6/-51 7/465
v8 6L6GC
pin4/466 5/465 6/-51 7/465

[Bruce / Mission Amps]

Short the vibrato pedal RCA jack from tip to ground and that should get tube 5 started.
Also, make sure you don't have the speaker jacks wired wrong... it will still make some sound but be very distorted and crazy low output.

[Beardsley]

Also, make sure you don't have the speaker jacks wired wrong... it will still make some sound but be very distorted and crazy low output.

Actually when I changed out the 470k the volume came up to normal. Im just worried about the high voltages now. I will try shorting the vibrato. Can I just use the footswitch?
Thanks for the response!

[Bruce / Mission Amps]

Actually when I changed out the 470k the volume came up to normal. Im just worried about the high voltages now. I will try shorting the vibrato. Can I just use the footswitch?
Thanks for the response!

Yes, but I didn't know you have the Vib Rev pedal for switching.
Those voltages are high but I wouldn't let that stop me.
The power tranny is probably a copy of the silver face PT which used a 5U4GB rectifier not a GZ34.

[pdf64]

'v4 7025
pin1/353 3/3.5 6/354 8/3.5 pin1 should be 270. '

The cathode voltage there is too high. Check the value - it should be 820ohms. Maybe you've go a 1k5 there?

[Beardsley]

Thats it! I had accidentally swapped the 820 and the 2.2k when i soldered them parallel to the caps off the board! so now my only high voltage is v5 at 448v but when I hit the vibrato it jumps down between 200 and 310. So is that normal?