CrazyMetalBeer said:
wow.
I also remember the amp making a "popping" sound every once in a while, that would come thru the speakers....dunno if this is any more valuable info...
There a number of things that can cause popping, but that's quite often a tube socket arcing. This is something you can check yourself. Unplug the amp, get a brite flashlight, pull the power tubes ( one at a time, or number them with a sharpie first if you want to pull all of them, so you can put them back in the same position. I'll explain in a bit why you want to preserve thier position ), and take a real good long inspection of the sockets. What your looking for is tracking.. burn marks from arcing. They can be micro small, so I use a magnifying glass to be sure, but usually it will be pretty obvious. Socket arcing is a cancer to the socket. The only fix is to replace the socket.
The reason you want to preserve the tube's positions are to preserve the symptom, and to keep any problems from migrating, and doing further damage. This will also make troubleshooting the distortion problem easier by not introducing other variables.
While your in there, give the tubes a good look. Are the plates ( the grey metal inside the tube ) discolored? That's a sign of them running too much current ( underbised ).
When your done, put the tubes back in and ( provided you didn't see any arcing on the sockets, if you did, get it to a tech ) power the amp up with the volumes on zero, no instrument, and watch the power tubes for 2 things, red glowing ( cherry ) areas on one or more of the plates, or arcing inside one or more of the tubes. Regarding cherry plates, don't mistake the yellow glow of the heater ( filament ) inside the plates, that's normal. When you see a plate glow, you will know it Immediately. If there is a soft blue glow around the plates, like a plasma cloud, that's OK too, it's a bit of gas in the tube ( some folks get quite anal about this, but honest, it's fine and common. Most of my Mullard's do it ).
The arcing looks just like lightening. It will be very intermittant, so watch for a bit.
If there are neither, then plug a guitar in, turn the amp up to your normal playing volume ( or when you notice the distortion ) and watch the tubes while you play. Sometimes it takes the extra current of playing to set off either cherry plate or arcing. Don't take a shortcut by playing first, following the proceedure I described, and stating the results to your tech will have him thanking you.
A couple of last things I want to mention, one regarding popping. Arcing inside an output transformer will cause loud popping. This is the slow death of an OT. Very bad news for nice collectable amps, but there are a number of excellent companies and custom winders that can duplicate yours. Hopefully that won't be the problem.
An old winder told me something when I started out many moons ago. He said " Never store an amp where you wouldn't want to sleep". I'll add to that, never run an output transformer coupled amp without a load ( the speaker ) . More OT's have been fried this way than any other. I've done it. You might get lucky and catch it before you hit that power cord, but.. enough said I guess..
( Solid state is another story, it's too much of a load that kills them, but that's for another day )
Hope this helps,
Bill
(707) 778-6565
