AMC CVT3030a Help for repair

[georgesgiralt]

Hello !
I've got this amp new in, say 1993/94. It has had some issues over the years :
When in warranty, one channel stop working, the importer's repairer did a terrible job, removing some connector and doing bad soldering job. But it worked.
Some years ago the B+ diode bridge went out and I repaired it changing the big filter electrolytic.
A week ago, one channel went out, blowing the fuse on the B+ supply. I thought that the diodes had gone south again. Alas, it was one of the left channel EL34 has lost it's vacuum (soldering a tube is not a good idea, but it worked for years).
I bought a couple of ElectroHarmonix Sovtek EL34EH and soldered them. This channel runs fine now.
But the other channel arced on one of the EL34 I thought it was caused by the opening having disturbed dirt and dust inside the box. I scratched the PCB between the two pins which smoke, and the put things back in. The bias was impossible to get on this channel : The 0V is impossible to get becase I get around the bias voltage..... So I suspect one of the FET (BS592 and it's associated PN2222A) to have blown. I cant source them anywhere.
So All your thoughts and help will be *vastly* appreciated !
Many thank in advance for your help and advice !