Hi everyone, this is my first post. i hope i get it right. teehee...

Anyway, i've got an old Lab Series L5 here from the late 70's. it went dead once so i gave it to a guy for a while to see if he could fix it. it came back with a new power supply and reverb driver pcb. It worked for a while but didn't sound near as good as it did before (not as much power, clipping at lower input, things like that.) after about 2 months or so it developed a much louder than usual hum. Then it just stopped amplifying any input, just a really loud hum, like if i were to hold onto my guitar cable and turn it up all the way. the compressor light just stays on and there's nothing i can do about it.

i was wondering if anyone could shed some light on my problem?

i have some basic electronics knowledge (graduated the basic electronics course at ft. gordon, georgia while training for 94F special electronics device repair)

i don't have a logic probe or an oscilloscope.
i do have a multi-meter, soldering iron, lots of time...

oh yea, i have schematics and wiring diagrams if it would help.

thanks in advance.

Edwards