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#1
05-18-2015, 07:29 AM
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Cap Job on the Twin
Wow what a difference. For a long time now my Twin has been wonky. The obvious thing was that it would get insanely hot, so hot you could not touch the metal faceplate by the power tubes. She also made some weird Zzzzz noises and had this low end distortion. I'd been using my Mesa as a replacement for years. Finally took it too a very talented tech in the area.
The good news was that the transformer was good so he replaced all the caps. What a difference. This is the first time on this '72 Twin it's ever been done so it's long over do. One of the things I really noticed now is that the Volume/Master Volume relationship actually does something. Prior to the fix I used to just leave the master on ten and adjust the main volume as needed. Now I can drive the tubes with the volume on ten and use the Master to dial it in. It's a Twin so it will never sound like a Marshall but it still is able to dial in some drive. I'm not sure why every one hates on the Master Volume Twins. The '72 apparently was the first year they did it. Anyway just me wanting to say Yay! I got my beast back. 
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#2
05-18-2015, 08:26 AM
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Electrolytic caps don't have a long lifespan and that goes double for older ones manufactured decades ago. Mostly these are used in the power supply - sounds like something went wrong here to push up the voltage and cause the overheating.
Electrolytics also turn up as cathode resistor bypass caps where they affect gain and voicing.
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#3
05-18-2015, 09:35 AM
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I think if the old ones had significant DC leakage, it could start stressing the power transformer.
Nothing like a freshly tuned up amp to make you smile.  I believe the master volume ones were mostly maligned for Fender's (technically CBS's) attempt to turn their amps into something they were never designed to be due to competition from Marshall, Mesa, and others. They still sounded great when run clean.
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"You don't have to be great to start, but you have to start to be great." -Zig Ziglar Acoustics 2013 Guild F30 Standard 2012 Yamaha LL16 2007 Seagull S12 1991 Yairi DY 50 Electrics Epiphone Les Paul Standard Fender Am. Standard Telecaster Gibson ES-335 Gibson Firebird
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#4
05-18-2015, 12:14 PM
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Yeah that was the thinking my tech had as well, that leaking caps could demand more voltage which could over heat. She's running like a champ now. New tubes all around as well.
I will say that the push pull thing with the Master volume sucks and pretty much every review online says the same thing. But I got a Twin because I wanted clean anyway. I can dirty it up with my Big Muff 
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