I am kind of suspecting something like this.  I noticed that the pcb, even on the preamp circuit, is a little brittle.  When I testing the led for the compressor I noticed the solder joints where starting to lift off of the board and looking a bit funky.

Thanks for the suggestions.

Yeah, I plugged the l5 into another known good cabinet and the popping was still there.  Although the speakers were mismatched when I got it I just put in the a 16 ohm replacement (red coat private jack).  The speakers sound great until the amp warms up.  Then they still sound great except for the popping.

Last night I dropped it off with another tech.  I think he will be able to make some progress.

Now that you mention it I am going to disconnect the tank and give it a shot, the reverb pot makes no difference to the sound.  If you listen to the file I attached a few messages ago you can hear it yourself. 

Just tried.  No dice.  Still popping.  I let is sit and warm up without a guitar plugged in and it started popping on its own even. 

Yeah I made sure.  The replacement is a Eminence of some make and a guitar speaker, but mismatched.  8 ohm rather than 16.  I have it disconnected with a new 16 ohm coming today.  I bypassed both and plugged the celestion from seymour duncan into it (my gig amp, works like a champ) and still had the problem so I know it is not the speaker.  It is such an odd sound, the way it repeats and fades.  The reverb is out too and it's location is a bit strange to me in that schematic.  I am going to bring in to another tech tonight, hopefully he can spot the trouble.  It really does sound awesome so I want to get it fixed.

And looking at the schematic here http://www.rru.com/~meo/Guitar/Amps/Lab/schem.html makes be believe the compressor is in the pre-amp circuit, which should be bypassed by plugging my guitar directly into the poweramp input....

Bypass the compressor meaning more than just turning it off?

By a little bit I mean 1 minute or less.

And.... it takes a little bit before it starts.  So something is warming up and then causing the issue I would assume.

I plugged the guitar straight into the power amp and still got the sound so I assume that means it is post pre amp.  I made a recording.  Sounds pretty awful in mp3 (was amr) but you will definitely hear the issue.  The first part is just straight through on the second channel.  you can hear the repeated crackle/pop.  Then there is a pause as I plug directly into the poweramp and you can again hear the same problem.  Compressor on or off does not matter.

Anyone know where I should start?  I think it sounds like some others problems that have been on here so I am going back to read those old posts again.

Well.... after 4 months the amp is back.  It works now but now it has other issues. The compressor is still out, and if I turn the volume up much it starts to pop almost like a blown speaker.  I will do some more trouble shooting tomorrow to figure out if its pre or power amp issues.  Seems to be affected the most when I turn the frequency pot down all the way and the mid range up all the way.

I wish he would join but he does not appear particularly comfortable with computers.  He is quite good but  old school.  If he hits a wall with this I will definitely ask him to post what he has done (even if I have to type it for him) and see what you guys think.

I think he is taking his time and enjoying it so I don't want to rush him.  He is pretty methodical (and careful) about it. 

He did pull p22 and I can ask what happened.  I plan on bugging him again this afternoon.

Apparently it is not that cr204.  He found only 5v heading to the preamp but now he suspects it is something in the preamp itself. .  He replaced one 741 opamp down by the reverb connection but that was the only piece he could get anomalous readings out Of on that board.  Everything on the power amp came out roses.  He said something about checking the opamps located on preamp.

He also said the compressor is working, just the low voltage is keeping the light off.

Wonderful!  I sent this to my tech...  Hell I will give it a try if he gets stuck.

Do you think it will be repairable?  Extremely expensive?  Not worth it?

Wow, thanks for the heads up.  I just dropped it off at the shop and sent them your notes and schematic.  Fingers crossed.  I don't want to send this back to Florida....