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Classic Reverb meltdown!

Discussion in 'Amps and Cabs' started by johnzias, Feb 19, 2009.

  1. johnzias

    johnzias Member

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    I just picked up a new Gibson R8, and plugged it into my CR this morning. I played for a good 15 minutes, both amp and guitar sounded great. I kept everything on while I sat down to my computer, save turning the volume on both pickups down to 0.

    After a few minutes I started hearing a hum, checked the guitar volume which was indeed off, played a few notes that sounded strained then unplugged the guitar from the amp, and the noise got worse. Looked in back and the right two 6L6's (it's a 100w), were glowing a very hot red, and the smell of overheating circuits became evident. I immediately shut the amp down. I mean I've played 125 straight gigs with this amp and was just remarking to myself the other day how reliable and durable it is.

    Any theories? Too early still to call Joe or Bill.
     
  2. Squigglefunk

    Squigglefunk Senior Member

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    tube went south probably
     
  3. johnzias

    johnzias Member

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    Ya think? I've never quite seen that result when a tube went, and it was two tubes.
     
  4. johnzias

    johnzias Member

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    Well I just happened to have 2 more Philips 6L6's, although one is teetering. You seem to have hit the nail squigglefunk. 25 minutes, so far so good!
     
  5. zoooombiex

    zoooombiex Member

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    Interesting that it was the right two that went. Usually in a 4x6L6 amp, the inner two tubes are paired, and the outer two are paired. (That was also true for my 100 watt K&M custom) If that's the case here, it means that something went awry in both pairs at the same time. Maybe just a coincidence?
     
  6. traviswalk

    traviswalk In the Great State Gold Supporting Member

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    Did you call Bill and Joe yet?
     
  7. drewl

    drewl Member

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    Actually No, the opposite is much more common.

    If two tubes redplated at the same time, it's more likely that those two lost their bias feed which they share. Possibly due to a bad phase inverter coupling cap or bias feed resistor.
    You'll know if the same two go nuclear again.
     
  8. zoooombiex

    zoooombiex Member

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    Interesting - the four 4x6L6 amps I've had were all paired inner/outer rather than left/right. (three were two-rocks, one a Fargen). But among other manufacturers, it is more common to pair the two left and the two right?

    In any event, I would guess that since this is another two-rock they probably did it the same way, and the two right tubes were not sharing a bias resistor. (otherwise, that was going to be my guess too). then again, they easily could have changed designs...
     
  9. johnzias

    johnzias Member

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    They must've changed designs zoooombiex. After describing the event to Bill, he said they were paired and that only one of the pair was the culprit. I won't throw them away because they are NOS Philips, but I need access to an old fashioned tube tester.

    Anyway, all is well with the amp.:love:
     
  10. TheArchitect

    TheArchitect Guest

    I had a bassman head meltdown in a similar fashion. It was resistors/caps/something that was feeding power to the tubes that went south.
     

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