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Topic: Blown fuse in a Twin |
Dave Meis
From:
Olympic Peninsula, Washington, USA
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Posted 26 Dec 2016 10:14 am |
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| '79 Fender Twin. Recent tubes and service. The 2 times before the 'problem', when I switched from standby to on, I got nothing..chased down the cables, ect., and when I plugged the guitar back in, it worked. OK. The next to last time, same thing..turned it on, nothing. Re-plugged the guitar, worked fine. The last time, I switched it on.. HUGE fart and blew the fuse. I haven't replaced the fuse and tried it again. Seems if it were the jack, it just wouldn't work, but no drama. Thoughts? Thanks, Dave |
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Michael Butler
From:
California, USA
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Posted 26 Dec 2016 11:48 am
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i would get back to your tech since it seems to have worked fine prior. no use is blowing more fuses.
play music!
_________________
please see my Snakeskin's Virtual Music Museum below.
http://muscmp.wordpress.com/ |
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Dave Meis
From:
Olympic Peninsula, Washington, USA
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Posted 26 Dec 2016 2:26 pm
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Pulled it down, gave it the 'sniff' test..no burnt smell, no traces.. replaced the tubes, and all seems well. I think it was an 'intermittent' tube..we'll see.  |
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Lane Gray
From:
Topeka, KS
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Posted 26 Dec 2016 6:37 pm
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One of the knowledgeable electronics guys (Fox? Marcus?) pointed out that the inrush current burns off bits of the fuse wire every time you power them up if you're using fast blow fuses, so that eventually your fuse won't survive its rated current. So it might have just burned out.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Mark Fowler
From:
Minnesota, USA
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Posted 26 Dec 2016 7:48 pm
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A customer had the same problem with his Dr Z EZG50, the cause was the rectifier tube. Doc's crew suggested using Sovtek brand, as JJ and others had history of failing, and that resolved the issue. There were no bad screen resistors or other problems.
While I was in there I added diodes to the tube sockets for protection on the road.
Mark |
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Dave Meis
From:
Olympic Peninsula, Washington, USA
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Posted 26 Dec 2016 8:24 pm
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| Thanks guys..had all the caps, ect. replaced about 8 months ago, but had some 'weirdness' with one of the Mesa branded tubes that were in there when I bought it. The PO said they were new, and I don't doubt it. They tested good. They would work fine for a few months, then get noisy (hum). I'd take it apart, clean everything, put it back together, it would work fine until it hummed again. Noticed when I tapped it, it would go nuts, so, tonight, I put in a new set of Tung Sol 7581A's I had, re-biased, and all swell now..been playing for the last 4 hours..no weirdness, no red plates..just tubal goodness! The fuse that blew was a 3A instead of the 4A that's called for, so I put in the 4A Slo Blo. Hoping for the best. Love my PP through that Twin, even though I swear somebody screwed it to the floor every time I take it to a gig. SS rectifier, and I've never had much luck with JJ's.. had a bad one right out of the box once, so I don't buy 'em anymore. Thanks to all! |
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Mickey Adams
From:
Bandera Texas
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Posted 27 Dec 2016 10:50 am
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Power tube failure, or even mismatching, will result in this as well as the rectifier tube. Bias probably needs to be addressed as well..
_________________
ARTIST RELATIONS: MSA GUITARS
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