First Revision Ampeg VT-22 Low and Distorted Output

[HNKTNK]

I have 2.5vac on pins 4 and 5, and yes, there's continuity purely because they are connected by a trace. Then I pulled it out and measured on the pins of the tube and it was open. So it seems like that is at least part of the problem

[HNKTNK]

Thanks g1, I'll make that change to the jack.

[g1]

Sorry, I think the 2 brown wires on those overlapping lugs are reversed. The lug that the white wire coming off impedance switch connects to should also connect to the tip terminal of 'ext.spkr' jack. The shunt lug should go to the sleeve terminal. Ring terminal should not be connected. (remove short brown jumper wire)

[HNKTNK]

Good deal, thanks again! I'm going to order a 12dw7 and go from there. Thanks for everyone's help

[The Dude]

I have 2.5vac on pins 4 and 5, and yes, there's continuity purely because they are connected by a trace. Then I pulled it out and measured on the pins of the tube and it was open. So it seems like that is at least part of the problem

Yes, you have to pull the tube to check filament continuity. If not you will measure across other parallel tube filaments and filament transformer.

[g1]

It seems like there's something I'm not understanding about the sends and returns. I'm running ext. amp from my v4 to the send of a gvt to test the power amp. I should connect a signal to the input of the gvt, correct? It doesn't seem to affect the sound when I adjust eq on the gvt.

Yes, that is correct hook-up. Perhaps the gvt send is pre-eq, but seems odd. What make and model?

[HNKTNK]

It's an Ampeg GVT 52 212. I've only ever used sends and returns for effects pedals, so running it that way is new to me.

[g1]

According to the manual, all controls except volume should affect the FX send. So you should hear EQ changes through the V4.
If the V4 power amp still has problems, you may not hear a lot of difference when changes are made to the gvt preamp.

[HNKTNK]

Should I be plugging my guitar into the input jack of the gvt or the unused fx loop jack?

[HNKTNK]

The way I had it set up was audio source>GVT input>GVT send>v4 ext.amp

[g1]

That is the right set-up.

[g1]

Also note that the V3 tube is required for the 'ext.amp' jack testing.

[HNKTNK]

That tracks. I have a show this weekend, so I'm going to throw a 12ax7 in there until the 12DW7 arrives. Thanks again for the help!

[HNKTNK]

I'm back because I'm still having the same problems.

A little recap- My output is low and the amp breaks up early. I would say it's about as loud as my old deluxe reverb, where before, it was very loud and very hard to get it to break up. Sounds the same through all cabs, guitars, cables, etc. The sound itself does not sound nasty. I just played a string of shows over the last month with it and it held up fine.

I have found several problems with it up until this point. The 12dw7 was faulty, but it seems as though that was really only affecting my ext. amp feature. I tried swapping it with a 12ax7 to see if it made a difference, which it did not. I also found that R207 had drifted big time. It was reading around 150k, if my memory serves me. That has been replaced. I also went ahead and replaced all of the power tubes, 12AX7s, 12AU7. No change there. I also forgot that the safety cap was still in this and it blew long ago. Before my problems started (I think). Sent it's guts all over the board. That has been taken care of. I've pulled and measured every resistor twice now, since I missed R207 the first time, and they all check out. I took voltages on all of the tubes and found quite a few things that are off. I'm hoping someone here might have some advice. I'll list all of my measurements with the my readings/what's on the schematic:

[HNKTNK]

V1
1. 233/230
3. 1.98/2.1
6. 187/195
8. 2.18/2.05
V2
1. 233/240
3. 2/2.1
6. 186/195
8. 2.1/2.05
V3
1. 322/325
2. 87/200
6.192/205
8. 1.9/1.8
V4
1. 207/200
6.195/200
8.0/9.7
V201
2. 208/192
3. 22/22
4. 149/140
5. 141/178*
6. 1.26/1.26
10. 322/325
V202
1. 101/112
3. 3.7/4.1
6. 251/270*
8. 5.1/5.6
V203
1. 116/115
3. .72/.76

Every power tube measures 522 on the plate and 522 on grid no.2 (pin 4).