Trouble with Ampeg V-4

[01redcobra]

Ampeg here has some issues. Signal not passing thru preamp. Probing for voltages at tube v4 looks ok, although voltage is high to all plates and getting audible noise while probing. Back to v3 and voltages are all wrong. Getting noise when probing 6-7-8 but nothing from 1-2-3. Voltages are as follows 1-389 2-124 3-263 6-118 7-0 8-1.8 . Replaced the c8 cap but still the same. I am baffled at this point. Schematic is attached. Thanks in advance.

[acorkos]

did you already replace V3?

[g1]

Lots of problems with bad solder connections on those boards, especially at tube sockets and higher wattage resistors. With the age of those amps on my own V4's I resolder all boards. If you have the time it's worth it.

[01redcobra]

Finally got a chance to work on this again and replaced v3. Still having the same issues.

[jrfrond]

Lots of problems with bad solder connections on those boards, especially at tube sockets and higher wattage resistors. With the age of those amps on my own V4's I resolder all boards. If you have the time it's worth it.

+1 on this. Resolder EVERYTHING first. If you have cold solder issues, all of the troubleshooting is worth zip.

[01redcobra]

Actually just found the problem. The shielded lead to the ext. amp must have deteriorated internally and was shorting the signal out. I found it when I was checking resistance values at r21-22-23. I disconnected the lead and started to get popping back when probing on the first side of v3. Thank you all for your help!