Questions/Help with SUNN BETA Lead repair

[seadflo]

 
ve had a sunn beta lead for a while now.
and recently, it suddenly lost all power unless the drive and level is turned all
the way up.
now, it still sounds VERY crunchy and loud, but i really liked it for the clean sound.
and it used to sound VERY loud and clean at 2 on the level with barely any drive.
Anyone have any leads on this.?
While I am by no means a genius in repair, i dont want to ditch this amp or just use it as an oversized distortion box.
I really like the amp.

Local repair says its not worth fixing..meaning..alot of money on their end.

but..
yeah.
any input for my ignorant self would be greatly appreciated..
thanks.

[mckinnon audio]

  Hi there,I could be wrong but it sounds like the IC's on the front end of the preamp are shot,that's why you have lost the "clean" sound and your drive level has to be increased to get any signal out of the preamp at all.Having said that,you can get the same sort of condition when the power feed to 1 or more stages is missing.I'd put a signal in the input and scope it through the pre.Also measure the volts on the IC's in the pre.Hope this is of some help,good luck Mel.