Odd problem/bugera 1990

[Tjfeast]

Hello all!!
New poster here!!
I've got this bugera that does something odd..
Turn on, warm it up, runs right then all a sudden it whines and starts powering down like I'd hit the power switch instead of the standby....then it starts to power back up and come to life...
Anybody got any ideas?
Thanks for your time!!

[The Dude]

Welcome to the place!

Here's the schematic:
http://music-electronics-forum.com/a...10356-1990.pdf

This could be many things. Do the filaments stay lit when the amp fades? Those amps are also known to have regulator problems- particularly the 7815. Monitor your +15V and see if it dies. If so, you may want to install a heat sink on the regulator and/or replace it.