power section needs "jump starting" every time i power it on/off

[cooldude666]

This one is driving me MAD. So when I power up my amp it's dead quiet- as in not amplifying. Signal probe shows me that the Preamp/pi are all working but then when I put my probe to the Grid of my power tube IT STARTS WORKING. At least it's consistent?? It WILL NOT make sound until I tap it with my probe. Once I tap it, it's good until I shut it off. No amount of yanking at the bias feed resistor will make it stop (well I'm sure that SOME amount would, but that's different!). What the $*!# could be going on here??

[loudthud]

Could be an ultrasonic oscillation of the power amp. Check for a large AC voltage across the speaker when the amp is in the silent mode. This type of thing is usually a lead dress problem.

[cooldude666]

Fixed it! At some point between putting this amp away to move, and starting this I began reworking the bias supply and never finished. I redid the bias circuit. It's good to go!! Amp still needs tweaking, I am positive I will need more help but for now- time to riff.