DRRI blowing fuses

Discussion in 'Glowing Bottle Tube Amp Forum' started by Strato50, Feb 18, 2020.

  1. Strato50

    Strato50 Tele-Afflicted

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    It pops the fuse occasionally. I put a brand new rectifier tube and power tubes in. Any other ideas why?It does fine for a whole gig then out of the blue at home it blows a fuse. It calls for a 125V 2 amp. I’m running a 250V 2 amp in it now. It’s working fine. But has it has me concerned it will blow at a gig. Any suggestions at what I might look at inside? Could it be a cap? I notice a slight hum at idle.
     
  2. uriah1

    uriah1 Telefied Gold Supporter

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    Replace the PI.
    I had a bad pi that kept toasting the plate resistor
    next to it that kept popping the fuse.
     
    Last edited: Feb 18, 2020
  3. schmee

    schmee Poster Extraordinaire Silver Supporter

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    Are you using Slo Blo fuses?
    When you changed tubes did you use OS or NOS Power tubes?
    When you changed tubes did you use a Chinese or Soviet rectifier tube?
     
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  4. Wally

    Wally Telefied Ad Free Member

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    has this amp ever blown the fuse anywhere but ‘at home’? If not, one might suspect some sort of surge in that home circuit that is taking the fuse out. If it blows elsewhere too, then one suspects something in the amp.....or as schmee alludes to you have a fast blow fuse there which is more susceptible to blowing than the slo blo fuse would be.

    fwiw, I have a DRRI in right now for a blown fuse......diagnosing I’ll be later today.
     
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  5. Strato50

    Strato50 Tele-Afflicted

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    I used all JJs. Replaced the PI with a JJ as well. It’s only blown the fuse at home. I’ve done two gigs with no problem. It’s done it twice at home. I’m pretty sure I’m using slow blow. I will check when I get home.
     
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  6. Strato50

    Strato50 Tele-Afflicted

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    Yes please let me know what you discover on it.
     
  7. uriah1

    uriah1 Telefied Gold Supporter

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    So you have tried it in different circuits at home?
     
  8. schmee

    schmee Poster Extraordinaire Silver Supporter

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    OK, yeah make sure it's a Slo Blo. I "fixed" an amp for a friend that was doing that (Mesa Boogie). He said he didnt trust it, it would blow a fuse at random times. When I checked it out it had normal fuse in it. Put a proper Slo Blo in and it been fine for a couple years now.
    I have had two bad import rectifiers. One Chinese, One Soviet. Bad from the get go. They flash when you turn the amp on creating a spike that blows the fuse often also. I like new tubes but in rectifiers I only use older USA/British tubes.
     
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  9. Wally

    Wally Telefied Ad Free Member

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    okay....the amp came to me with a blown fuse. The pilot light was blown. All tubes show no shorts, but the power tubes are worn out....very weak so they will be replaced. With the amp in standby for a couple of minutes, the Russian rectifier tube flashed...and blew the fuse. So, I put in a NOS Sylvania 5AR4. With all tubes in and in play mode, the fuse is holding. I chalk it up to a rectifier tube that can not handle the job. I have never had a JJ GZ34 go bad on me, but NOS is the way to go for rectifiers, imho. I’ll install a fresh pair of 6V6s, rebids, and I think this one will be good to go.

    correction: this rectifier was the original GT labelled JJGZ34/5AR4.....I stand corrected. This amp is five years old. They did not want to pony up for the NOS Sylvania......they will be replacing this rectifier again in a few years...and hopefully all it will take out is a fuse.
     
    Last edited: Feb 18, 2020
  10. trxx

    trxx Tele-Holic

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    I switched on my super reverb this morning and had no power to it. Yipes. The fuse was blown. I pulled the chassis and gave it a look over, checking resistances of the speakers, tubes, diodes (rectumfrier), output transformer, and all looked good. No shorts. I had played it a few hours yesterday, adding a digitally controlled analog delay pedal to the pedal chain, which was having power issues from the getgo. Apparently this pedal is very picky about power, specced for a 150mA current draw, but I couldn't get it to behave until I put it on a 500mA output of my pedal power supply. Anyway, I replaced the fuse in the super reverb after checking things over, switched it on, observed it for a bit, and all seems well. I'm wondering if there was a correlation between that new pedal and my blown fuse this morning. The power running to my work shed where the amp is sitting isn't exactly heavy duty and has been known to trip a breaker on occasion.
     
    Last edited: Feb 22, 2020
  11. Strato50

    Strato50 Tele-Afflicted

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    Update on the deluxe. It had a shorted cap. So my tech replaced all the caps with FTs and he upgraded all the cheap stuff throughout the amp. It really made a huge difference. The amp sounds so much better. He said the caps that were in there are some of the cheapest he has ever seen.
     
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