serge knobs

[Plinio Andres Barraza]

I have been keeping up with synth-diy but not posting much, Now I need the
list's help on a couple of things:

-I am a determined beginer synth builder and managed to get my hands on a
scope.  I saw it working before I took it home, but later, after being 
on for about five minutes, the screen went blank and never again showed
anything.  I let the scope cool down and still nothing, it powers up fine
but no display.
The scope is a Tenma (two channels and and up to 20 mhz), anybody know it?
I would really like to fix it if anyone has manuals or even
troubleshooting ideas.  

-also, could someone suggest a procedure for testing integrated circuits?
I wonder if its possible to figure out what the pinouts on a salvaged
piece are, (the IC in question has no writing on it but has a huge heat
sink, I thought it might be a stereo amplifyer by the way it was connected
inside the record player I picked of the sidewalk)

Thankyou
Plinio