Genelec S30 repair part2

Hi,
Hello,
I trying repair Genelec s30's.
- its a three way active speaker

- bass, mid, treble has it own amp

- changed many parts and got it running.

Problem is treble amp offset reads -32 VOLTS when COLD!!

- treble amps bias is fine

- When amp heats up dc offset drops to +- 50mv, this is withing Genelec specs

- Dc offset bounces a lot when hot, from 50mv to 10mv then to 70mv and back to 50mv

Bias is stable when hot

- Genelec specifies that amp should be measured hot, but this is way too much when cold

- when this amp is working normally, offset is max 200mv when cold. (I have many S30 amp boards that work well)

- offset trimmer pot is tested and ok

- the whole treble amp board was resoldered just in case, looking for bad connection, no changes

- When amp is hot and its turned off for a couple of seconds, DC offset is immediately -5.00 Volts from -50mv. And starts super slowly rising back to 50mv

Where is the fault?
 

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Last edited:
Hello Sir, i have bought a pair of Genelec S30 speakers with some problems. I have found a service manual online. But there is no text and explanation where to measure like yours. Is it possible to send me your service manual, or a link where i can download it myself? Thank you in advance. Greetings Martijn