Amp winks off. Blown fuse. Bad rectifier tube?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Kiwi, Sep 25, 2006.

  1. Kiwi

    Kiwi Silver Supporting Member

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    Was playing my Germino Club 40 quietly when the sound went off. No lights, no glow on the amp head.

    Mains fuse (3 amp, 250v) had blown. Replaced with spare, which blew again when I took it off standby.

    Recalled Conventional InterNet Wisdom: Bad rectifier tube.

    Replaced the JJ brand GZ34 with new one. Replaced 3 amp fuse with only available spare, a 2 amp fuse. Worked fine.

    Rectifier tube went bad, then? I will go get the correct 3 amp fuse.
    Anything else to be careful of?

    Kiwi
     
  2. Blue Strat

    Blue Strat Member

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    If the 2 amp fuse held, it was probably only the rectifier.

    More ammunition for the NOS argument.
     
  3. Kiwi

    Kiwi Silver Supporting Member

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    The good news: I remembered to include a spare GZ34 in my last order from ya. The bad news: I ordered a JJ GZ34! = same as what fried.

    I put in the correct 3 amp fuse and a new JJ GZ34, it seems to work OK now. But ... NOS lasts about forever, is that the idea?

    =K
     
  4. Blue Strat

    Blue Strat Member

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    Maybe not forever, but is 30 years close enough? ;-)
     
  5. Texasamp

    Texasamp Member

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    Just use a Sovtek 5AR4 ribbed plate. Well known as the universal soldier in rectifier tubes. The always give me a bit more B+ and last. Only 8 buck a pop. Unless you want to used this below. These will out live you, but you will pay dearly. I was lucky and stumbled across a bulk of 50 of the RCA branded Mullards new in the box.

    [​IMG]

    Regards,
    Darrell-
    Texas Amplification
    http://www.texasamp.com
     
  6. StratTone

    StratTone Member

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    I was just at a gig on Wednesday playing my Crate V15 and it started to lose sound. In and out like a cable then finally nothing. Looked at the amp and no power. Blown fuse. :(

    Next day I put a fast blow 3/4 amp 250V fuse in (which was all I had) and it blew right away. (its orginal was a slow blow 3/4 amp 250V)

    So anyway the only thing Radio Shack had was a 1 amp 250 slow blow and it is working fine. I'm gonna order a 3/4 amp 250V slow blow and see if it holds. I wait to play it until I get the correct fuse. I still don't know what caused it though. Any ideas?
     
  7. Blue Strat

    Blue Strat Member

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    Sometimes fuses just blow for no reason. Something could be lurking inside though, so be careful. Most amps will run on fuses with 1/2 the specified rating (slow blow), at least at half volume. A good test, without using a ammeter, is to see if this works. If not, you likely have another problem.
     
  8. AdmiralB

    AdmiralB Silver Supporting Member

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    Slo-blo fuses can handle inrush current that'll pop fast-blos. I had an AC30 that started popping fuses; I replaced the rectifier (a Mullard), and it held, so I figured the tube was bad.

    Later I put the same recto in another amp that was fused by a slo-blo, and it worked fine. The inrush to the recto's heater was enough to trip the fast-blo in the AC30 but after it settled down it worked fine.
     
  9. fast ricky love

    fast ricky love Supporting Member

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    Interesting... I just had the same problem with my '66 DR. As soon as I turn on the amp the fuse would blow. Even in standby. Went thru 5 fuses before I tried replacing the rectifier. Problem solved. Didn't think it'd be possible as the rectifier I had was a Mullard. Oh well, there goes $100!
     
  10. rockon1

    rockon1 Member

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    My V32 is hard on tubes running them at 13.5 watts at idle. Its eaten (redplated) a couple since Ive owned it. Not sure if the V15 is biased the same. As with any amp I'd be leary of running it with a higher than rated fuse.Bob
     

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