Crate G130CXL

[punkykatt]

Hey Guys, I have this amp on the bench.   https://docs.google.com/fileview?id=0B_cPagiySScIMTc0YzQ2ZDktZjNlZS00ZmIyLTkwZDEtNDM1ZmNhZGU4MDIy&hl=en.    The amp works great for about ten minutes then gives a loud pop through the speakers and the amp hums. While in that state no guitar signal comes through the speakers and none of the switches work for the clean/dirty, reverb, and chorusing effects. It pops again and goes back to normal. I tried chop sticking and poking around trying to make it do it with no luck. I re- heated the solder joints on the power amp pcb , no change.  Sometimes this condition will last for a second or two and sometimes last until I shut the amp off and still be there when tuned back on.  Its got a mind of its own.  Any help is much appreciated.  Punky

[PRR]

> joints on the power amp pcb

Why would it be on the power amp?

Have you tried out and in at each send/return pair?

> While in that state no

Does the Power LED stay lit?? There's way too much stuff in that amp, you need ALL the clues you can possibly get.

> chop sticking and poking around

Good plan but doesn't always find the fault.

Just cuz it's easy: lift the 11-pin connector. If you have contact cleaner or a typewriter eraser, freshen the contact surfaces. Fixing a big Yamaha with that connector was almost that easy.

Then.... I'm thinking good alligator clips and a DC voltmeter. Probably an iPod-amp adapter so you can leave it "playing" while you do other stuff. See what voltages change when it POPs-off. Start with the power supply rails.

There's +/-15V from the main board to the preamp board. Pick a place to monitor. This amp has WAY too much stuff in it, and the routing is the typical maze. C81 C82 are important power points and easy to find. This may be a case where you wish for a DIP adaptor so you can monitor DIP IC pins without shorting.

If the DC stays up (but the POP makes me think there is a DC fault), then you may have to set up to signal-trace, see where signal gets lost. Of course you will get lost in this overcomplicated maze, but look for places which have signal then don't have signal.

[punkykatt]

Thanks for the informative reply PRR. Yes, the power LED stays lit all the time. I will try your suggestions to narrow down the problem.

[punkykatt]

finally had a chance to fiddle with this amp again. BINGO, JACKPOT.  Thank you thank you thank you PRR.  Problem was with the 11 pin connector on the power amp board.  I do have to say, for a S/S amp it sounds pretty good with those fat jazz chords and octave solos.  Thanks again Punky