Smokin' Joe II oscillation

[powdog]

Hi all. Just finished a Smokin'Joe II from T. W.'s website. It sounds great except when the Master Volume pot is at either extreme turn. At "0" the amp squeals or hisses, and at "10" the amp motorboats. In between it sounds great. The tubes are good from a working 18 watter, and all passive components are new. Any ideas and help would be greatly appreciated.

[Tom Phillips]

Quick Question.
Does this happen only when the pot is cranked to the stops at 0 and 10?
Tom

[R ski]

If that design has a feedback from the output of the audio to
some where back to the splitter circuitry, temporary disconnect.

If those issues clear up.

Then your wires need to be exchanged on the windings of your output transformer's split windings. The feedback can be reconnected

[powdog]

Hi Tom. I swapped out shielded wire from power amp to MV pot, which cured the motorboating and noise at "0". I now only have a little screetching when pegged at the "10" position. The noise ends quickly as soon as I back off. Everywhere else the amp sounds great.

[Tom Phillips]

Sounds like you may just need a little bit of wire dress work. Moving wires around using the chopstick method may be in order. Pay particular attention to the grid and plate leads. If any need to cross each other, make sure they do so at right angles.
Tom