Another TSL100 bias drift problem

[drewl]

Hey, $300 plus labor for a $1000 amp isn't bad.

[g1]

All good points above, but I'll remind that he did mention it was for a friend, so I assume he's willing to give away free labour but not parts.
That being said, I've done the same for family, and ended up spending so much free labour on things, that I end up wishing I had just shelled out cash for someone else to fix it instead.

[GainFreak]

Quick report on the case. It looks ugly but it worked at least temporarily until my friend gets the replacement board.
After lifting the bias circuit and coupling caps from the board the bias drift issue was solved. I left the amp on for several hours to make sure.
However there's still some voltage creeping in the PI section. Pins 1 and 6 started at 275V and 260V. After several hours they were reading 298V and 251V. B+ voltage was and remained around 465V, HV at the PI junction was around 400V.

All good points above, but I'll remind that he did mention it was for a friend, so I assume he's willing to give away free labour but not parts

If it wasn't for a friend but I had to charge for it I would have done it anyway because where I'm from I would charge (parts included) much less than the cost of a new board. Although it's a temporary solution not everyone has a replacement amp and/or the means to get one soon.