I got this from the other guitarist in Chattanooga punk sensation 40oz. Folklore. Here's a quick list rundown of wha happen.
PROBLEM:
Sound fades out and sometimes fades back in - as if someone was turning the amp on and off.
DIAGNOSIS:
1. [Tubes] it had EL34's in it, but this model was made for 5881's. I'm pretty sure you can get away with swapping them around, I've done it for a while in other amps. I had some JAN PhillipsECG 6L6WGB tubes that I put in it to try. NOTE: Some of these actually did use EL34's, you can tell the difference by looking at the value of the power tube's screen resistors.
I noticed that the tubes were redplating like a motherfucker, so i swtiched them out with some 6L6GB's I had and they still redplated - I could smell the tubes burning up. Nasty! At this point, I'm like 'FUCK WHAT'. So I just crank down the bias pot to lower the heat on those tubes. This seemed to do the job.
The amp seemed to be working ok and I thought maybe it was just the tubes, but then it starting the 'ol cutting out trick again, which is annoying as hell. I messed around and looked all over but didn't notice anything out of the ordinary. I noticed only the phase inverter 12ax7 was lighting up and decided to swap around all the 12ax7's to make sure they all lit up in that same spot - they did, so they were all ok. I plugged my GOTH LES PAUL into the FX Return and it worked and sounded great and I found myself relieved about having a fully operational power section.
2. [Preamp] So, now I know it's some shit in the preamp keeping these tubes from lighting up, I finally narrowed down the problem enough to find some useful information on this here internet. Apparently there is a very common problem with some of the DSL models in which a bridge rectifier that supplies DC voltage to the preamp tube's heaters gets so hot that it melts it's own solder joints causing the 12ax7's to shut down. People were replacing the actual bridge rectifiers thinking they were the actual problem, but I doubted a component like that would fail without being physically destroyed.
REPAIR:
I unscrewed and flipped over the preamp board and went through with my BABY SIZE FLASHLIGHT to find any shitty solder joints - there were quite a bit. NOTE: The overall build quality on this thing seems rather shit compared to other amps I've had the pleasure of glancing into (but it may have been fucked with before?). Anyway, I reflowed and resoldered all bad joints I could find and especially focused on all the bridge rectifiers there. I turned the amp on and fiddled around a bit more with the soldering on some bridges and it seemed to be working. I left it on for quite a while and checked back every so often and it's been stable.
TO DO:
1. Riff the shit out of it and see if I can fuck it up again
2. Bias the 5881's or maybe put the el34's back in and bias them right
3. Record some clips!
Here are the bridge rectifiers. They turn the AC voltage into DC voltage for the preamp tube heaters. They overheat and fuck up their solder joints causing this amp to be a pain in the dick.
