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I've got an ampeg VT-120 Triax head that's giving me grey hair. It's developed loud popping that starts as the amp warms up and turns into a deafening storm of static and pops.
To give a little history. I've replaced the power tubes and they're biased properly. I've cleaned and retensioned all the tube sockets, jacks, pots, switches and replaced the power resistors and plate resistors and some suspicious coupling caps all with no result. The filter caps look like they've been replaced recently.
With v3 (12au7) removed there is no popping. I've replaced the coupling caps and plate resistors in that section. With v3 in and v4 removed there is just the odd quiet static pop. Jiggling the tubes or sockets does not seem to have any effect. I have subbed in many different tubes without any luck. Chopsticking also yields no results.
The amp itself is a real pain in the ass to work on so I'm curious if anyone has any ideas or suggestions while I steel my resolve and prepare for more toil.
Schematic http://www.thetubestore.com/lib/thetubestore/schematics/Ampeg/Ampeg-VT120-Amp-Schematic.pdf
To give a little history. I've replaced the power tubes and they're biased properly. I've cleaned and retensioned all the tube sockets, jacks, pots, switches and replaced the power resistors and plate resistors and some suspicious coupling caps all with no result. The filter caps look like they've been replaced recently.
With v3 (12au7) removed there is no popping. I've replaced the coupling caps and plate resistors in that section. With v3 in and v4 removed there is just the odd quiet static pop. Jiggling the tubes or sockets does not seem to have any effect. I have subbed in many different tubes without any luck. Chopsticking also yields no results.
The amp itself is a real pain in the ass to work on so I'm curious if anyone has any ideas or suggestions while I steel my resolve and prepare for more toil.
Schematic http://www.thetubestore.com/lib/thetubestore/schematics/Ampeg/Ampeg-VT120-Amp-Schematic.pdf