I was chasing the extra hum in the SVT-CL few days ago - well it wasn't that bad, but it did not depend on tubes, biasing and volume, it was just more than I know these amps should have. I disassmbled it to clean some places - found a suspicious power supply 100uf cap which I replaced - along with main input jack, 220ohm screen r's with updated handling etc. It was running the same (the same extra hum), so I thought I disassemble it once again and look for the dirty grounds or something else maybe.
When I put it back together, shortly after I hit standby, both RED and GREEN bias light were lit, horrible, super loud squaling noise in the speakers appeared (then I shut it off) and it smoked the R14.. well quite unusual place to blew one!? I have disassmbled it 3 times already, looking for a reason, cleaned and looked for solder problems, PCB trace problems, measured all the components and I see nothing suspicios. I even took a preamp from another SVTCL to be sure it's not there (changed the driver tube and the 12AU7s too). Now running out of the 220ohm R14s and no idea how to trace the real problem...
When I put it back together, shortly after I hit standby, both RED and GREEN bias light were lit, horrible, super loud squaling noise in the speakers appeared (then I shut it off) and it smoked the R14.. well quite unusual place to blew one!? I have disassmbled it 3 times already, looking for a reason, cleaned and looked for solder problems, PCB trace problems, measured all the components and I see nothing suspicios. I even took a preamp from another SVTCL to be sure it's not there (changed the driver tube and the 12AU7s too). Now running out of the 220ohm R14s and no idea how to trace the real problem...
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