The Amp Garage

Are you using a reverse audio pot for the intensity?

I have a few marginally related fuse questions/observations to ask the hivemind. 1: I worked on a couple amps in the past week that have series mains fuses, presumably to hedge against user error. Curious if anyone has thoughts or opinions about this. One was in an swr workingmans amp, the other was...

I believe you want "garnet" shellac. It takes more coats than you might expect to get a deep color. I mix it so it's a pretty dark brown in denatured alcohol, but not so thick that it won't dry properly. I have only used it on wood, so YMMV with tweed.

I was under the impression that low voltage esr testers weren't necessarily accurate for high voltage caps. That atlas tester is putting out ~12v? I have also measured plenty of old electrolytics that have blown their guts but still test OK on an LCR meter. Sometimes the amp isn't even that noisy; m...

I was referring to a single wire transmission line, not a lack of a ground wire. I don't think they typically fluctuate so much to give an audible voltage drop, but might under certain circumstances. Not an expert, I've just heard of some weirdness in rural areas. https://en.wikipedia.org/wiki/Singl...

Sometimes if you pop the tube in the freezer for a bit, the condensation will show an impression of the worn off screen print when you take it out.

Not sure what your cabin is like, but assuming it is more rural than your house you could have some power distribution weirdness. Maybe low or inconsistent voltage from the utility, maybe the correct voltage from the utility but you have a single wire earth return system or some other oddity. Can te...

+1 for using a toroid. I'm not sure what benefits there would be for having separate power transformers, but you can stack toroids on top of each other. You could also do one transformer with seperate windings. Something like this would work if you're ok using a SS rectifier. https://www.antekinc.co...

I'm probably conflating memories of solid state bass amps and powered mixers, or some other category of things I try to avoid working on which glow brightly and sometimes won't turn on all the way with a lightbulb limiter...

One caveat with the scrubbing, heating, alcohol method; I have seen a few where the backer board gets charred. Sometimes you can lift the top board slightly and pull the backer board out without disassembling everything, then scrape off the carbon, add some fish paper, etc., or just replace the boar...

Your mixer is going to glow brighter faster than most tube guitar stuff. Presumably, everything is solid state, so there isn't much warmup time before it pulls full current, and the reservoir caps are going to be massive compared to what were used to in tube amps.

All of the caps look West German. Think I spot F&T, Siemens, Frako. I wonder why they put the power tubes by the input and the preamp tubes in the middle?

I don't think temperature rating necessarily means anything in isolation, it's not a hard limit. It's that temperature at a specific ripple current and voltage for a certain amount of time. An 85c cap with otherwise better specs will probably outlast the 105c cap at 105c. No idea how much you need t...

I don't think I have seen 105c axial electrolytics from Illinois but I could be mistaken. Haven't worked on a fender with prematurely bad IC brand caps in the past year or so but I used to find them somewhat regularly and not just hotrod series. Guessing many of the premature failures end up being w...

That extra 3 is probably just a typo. Usually people would be asking “.003 vs .0003” (big difference) not “.003 vs .0033” (no difference). Not a typo. There are different standard values of components depending % tolerance. You need enough values allowing 5%, 10%, 20% or whatever in between without...