After forty-eight years I finally did it!

Discussion in 'Amps & Cabs' started by Bob Womack, Nov 11, 2018.

  1. Bob Womack

    Bob Womack Active Member

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    After forty-eight years I feel like I've finally joined a fraternity - "those who have fried an amp!" I was playing along merrily, a week ago, at bedroom volume, when my twenty-year-old Marshall JTM60 went HUMMMM... Click... and silence. I know, I know, these are known to overheat and no-one likes them but this one has been great for me. I use it mostly for rehearsal and at the studio.

    The power light was still on but I shut her down immediately and let her cool. The fuse is good. The trannies look pristine, no color or leakage. There was no smell and I didn't let the smoke out. Never let the smoke out. I opened up the tube cage and checked the original 1996 Huntsville/Petrograd Svetlana EL34s that are set horizontally at the bottom of this chassis. There was no carbon trace on the pins, however, one of them had overheated to the point that the envelope melted (!) and deformed inward in an inverted bubble. The silver at the crown of the tube was a little oxidized away but there was no hint of singeing on the plates. Obviously zapped. I know: I should have replaced the tubes long ago but I'm used to colder biased Traynors that use up a pair of EL-34s about once a century.

    I trundled the amp off to the best tech in the area and crossed my fingers. Five days later I got the call and picked up the amp. It is now home and happy. It turned out to be the cooked tube which eventually popped a resistor which blew a fuse. They put a new pair of power tubes in there and a new resistor and fuse and checked out everything and biased the tubes. The bill came to $124.50 including a pair of JJ EL-84 tubes ($42) and the other components and fifteen minutes of jaw-jacking with the tech. Not bad at all. It looks pretty good for a twenty-three year old amp, eh?


    [​IMG]

    While it was gone I shifted to another amp but it really wasn't doing nearly as good a job. It's funny how with certain gear you can just put yourself on autopilot and focus on nothing but the playing. It's like comfort food. Comfort gear!

    Bob
     
  2. cerebral gasket

    cerebral gasket Well-Known Member

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    Good to hear that none of the magic smoke escaped. The fuse did its job to prevent any major damage.
     
    Last edited: Nov 11, 2018
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  3. Norton

    Norton Well-Known Member

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    Those jtm’s run hot and are notorious for melt downs.

    They always sound pretty damn good!
     
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  4. Bob Womack

    Bob Womack Active Member

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    Thanks, guys!

    Once I got the amp back, all shiny and new-sounding, I felt that it was time to perform a small piece of maintenance work I've wanted to do for a while. The Tolex that wrapped around the top panel had been slowly disconnecting itself over the years and hanging down over the corners of the control panel. It wasn't a problem but it had nagged at me for years and years and I thought the old girl deserved this little bit of TLC at this point. First, I removed the chassis which was secured by seven screws including one that went in from the right side. Unscrewing all those was made very easy by the Dewalt power screwdriver my wife gave me for Christmas. Then I applied small gobs of E6000 glue to the underside of the Tolex with a toothpick, pressed the Tolex into place, and applied a carpenter's spring clamp to each side to hold it.

    [​IMG]

    Once it cured I replaced the chassis, plugged everything back in, tested it, and put the amp back into service, now looking as great as it sounds!

    [​IMG]

    Bob
     
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  5. DaveInSoCal

    DaveInSoCal Active Member

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    I am a member of that fraternity! My new (used) Blackstar HT-60 fried at band practice. I was merrily playing along and then I noticed I couldn't hear my guitar any more. My drummer says "Dude, there is smoke coming from your amp!"

    That baby was toast! Luckily I had paid for the GC warranty, I brought it back to the store and swapped it for a 1998 Marshall JCM2000 DSL50. It worked out great, I never could dial in a good tone on the Blackstar, the Marshall on the other hand is perfect!
    Yay me!
     
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