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Post subject: Twin Reverb Overheating
Posted: Sun Dec 16, 2012 9:58 pm
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Aspiring Musician
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Location: Oakland Tennessee
My late 70's silverface Twin is getting unusually hot and when it does this it starts getting static sounds in the speakers. It blew a fuse a while back and I replaced the fuse. It hasn't blown another yet but it gets hot. I mean hotter than it should. I use an RC booster and a tube screamer but it acts up even when I don't use the pedals after I play it for say an hour or so. Any suggestions? Thanks in advance.

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Post subject: Re: Twin Reverb Overheating
Posted: Sun Dec 16, 2012 11:21 pm
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I'd have the amp's output tubes bias checked, for starters. I wouldn't use the amp until this is done. Prolly will need a good tech to look it over.


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Post subject: Re: Twin Reverb Overheating
Posted: Sun Dec 16, 2012 11:24 pm
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The entire power supply (to include the biasing circuit) should be inspected for age-related issues -- filter caps, biasing caps, power-rail resistors, and the diode stack. Anything out of spec should be replaced. Are the power tubes red-plating? If so, it's time for new bottles. The late '70s ultra-linear Fenders demand a 6L6GC-STR due to the 500VDC found at the plates. Tung-Sol offers a STR415 equivalent that should work well in your amp. I recently installed a quartet of these in a 1980 Bassman 135 head (similar in many specs to a Twin Reverb). Thus far they've been great performers and they're reasonably priced (about $85 for a matched quad).

HTH

Arjay

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Post subject: Re: Twin Reverb Overheating
Posted: Sun Dec 16, 2012 11:43 pm
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Arjay,

Glad you like those new Tungsols. Nice to have new black plate option that can handle hefty plate voltages. I think that these tubes look like potential winner in non-UL TR and BMR, as well as UL amps.

I know of a few ppl with UL MacIntosh amps that have had good success with the TS. At least in the last year.


Last edited by BMW2002Ti on Mon Dec 17, 2012 8:07 pm, edited 1 time in total.

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Post subject: Re: Twin Reverb Overheating
Posted: Mon Dec 17, 2012 6:17 am
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Thanks guys.

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Post subject: Re: Twin Reverb Overheating
Posted: Tue Dec 18, 2012 2:24 pm
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BMW2002Ti wrote:
Glad you like those new Tungsols. Nice to have new black plate option that can handle hefty plate voltages. I think that these tubes look like potential winner in non-UL TR and BMR, as well as UL amps.


I'm not so certain. For owners of early blackface amps such as the Bandmaster, Vibrolux Reverb, Pro Reverb, or Super Reverb (ie: platforms with 425 to 460 VDC at the plates) and who rely strictly on natural power-tube compression and harmonic distortion for their overdriven tones, the Tung-Sol STR415 may not be the 6L6GC for them. With 500VDC capability, they stay pretty clean throughout the amp's spectrum. In those amps, I think JJ's, Sov-Tek's, EHX's, or the beloved Winged C's are the way to go. At least as far as contemporary bottles go.

JMOOC

Arjay

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Post subject: Re: Twin Reverb Overheating
Posted: Tue Dec 18, 2012 3:10 pm
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Arjay, ok "sounds" good. I've been using 7581A (STR-415) -> [GE, Sylvania STR-415, and Philips ECG] in most BF and SF Twin Reverbs and Bandmasters. Most ppl with these amps want clean tone with tons of headroom. You know, crazy lap steel players and Ted Nugent types that love that 6L6GC super crunch.

I may try the TS in my VLR, just for giggles. My bet is that they are going to take awhile to break-in.

BTW... getting a delicious 1964 Gretsch 6156 Playboy in for fixing. This amp runs righteous GE BP 6973s. Ever heard of this tube? Like an EL84, but with a lot of headroom. And a wonderful glassy shimmer. Check out the YT, esp with those stock Fender single pups.

http://www.youtube.com/watch?v=0j3x00UPvWQ

http://www.mif.pg.gda.pl/homepages/fran ... 6/6973.pdf


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