You could have a shorted capacitor or a defective op-amp (fed supply voltage by that resistor).
Still no sound.
Changed U100, R111 and R112.
Problem of the burning R111 and R112 is fixed now, the short on U100 is gone.
Do you perhaps have a diagram from the filter pcb?
Changed U100, R111 and R112.
Problem of the burning R111 and R112 is fixed now, the short on U100 is gone.
Do you perhaps have a diagram from the filter pcb?
I've never seen a diagram for the preamp board.
Confirm that you have ± supply voltage on the PS pins of all op-amps.
Have you operated all pots and switches through their entire range while listening for audio to see if it ever played through (even just for an instant)?
Confirm that you have ± supply voltage on the PS pins of all op-amps.
Have you operated all pots and switches through their entire range while listening for audio to see if it ever played through (even just for an instant)?
New update, literally every op-amp/component which delivers VCC + and - to the TL074c are shorted/burned.
Must have been a big voltage spike.
Need to order some new ones. Will be continued 🙂
Must have been a big voltage spike.
Need to order some new ones. Will be continued 🙂
It's very common for people to power up the amp without having everything clamped to the heatsink. For the 15v regulator, this generally means that it will fail and drive full positive rail voltage to the regulated +15v supply. I did this on a 92001 and it not only did the damage that you're finding but it also blew out all 3 of the fans on the heatsink. The fans were connected to the 15v supply and caused the regulator to heat up more quickly than I expected.
The output mosfet's are IXFH30N50P probably, I found overhere 7 mosfets from the repair of this particular amp.
Last edited: