Sansamp Classic Fet preamp problem

[Ngr]

Hello,
I have an old Sansamp classic, sometimes ago it began to sound pretty bad with no sound at all at extreme settings. I contacted Sansamp and they sent me a fet preamp board. I installed it and after some time the problem came back. They sent me another Fet board (BTW their customer service is AWESOME) and this one blew too. There must be something in the main board or in the remaining components that makes the fet preamp go bad.
Any suggestion? Did anyone had the same problem?
Thanks

[pedalgrinder]

i personally opinion only think that one of the fets is biased way to high and taking it out but thats only an assumption. most fets don't like being biased to a point where there being driven to hard. they will take it for a while but will give way if you giving it extra hot signals because they have a really high input impedance. so anything feeding it thats extra hot will essentially give it a guts full. Just my thoughts