PRRI Owners...Reverb Hum?

Discussion in 'Glowing Bottle Tube Amp Forum' started by DennisM, Jan 24, 2019.

  1. DennisM

    DennisM Tele-Meister

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    Just wondering if any other PRRI owners experience reverb hum. I normally play between 3 and 4 on the knob, and I notice a low level hum. Turning the reverb level to 10 results in pretty loud hum and some feedback.

    I've tried different tubes, cables and playing with the position of the tank. Nothing seems to help. Is this a normal trait of the PRRI? Any Fixes?
     
  2. tubejockey

    tubejockey Tele-Meister

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    Make sure the tank is plugged in correctly. They make a lot of noise if they are plugged in backwards. Also make sure the tiny wires inside the tank haven't broke. In some extreme cases of feedback you may need to wrap the tank in bubble wrap, put it back on the bag, and screw it down.
     
  3. Delta Blues

    Delta Blues Tele-Afflicted

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    My DRRI hums when turned up. I'm thinking of switching the tube to a NOS GE to see if it helps.
     
  4. DennisM

    DennisM Tele-Meister

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    Thanks. Yeah, this tank won't even work if its plugged in backward. To be sure, is it out from amp to in on the tank?
     
  5. clintj

    clintj Friend of Leo's

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    I chased a low level reverb hum in my BFSR clone, turns out a NOS Philips tube 12AT7 stopped it. This was after I ruled out grounding, tank orientation, cables, etc.

    Sent from my Pixel 2 using Tapatalk
     
  6. 7171551

    7171551 Tele-Afflicted

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    With my '68 PRRI the reverb is fine until the vibrato is engaged- if the "intensity" control is up around 5 it starts to sound like a helicopter and then feeds-back with growing intensity. I love everything about this amp apart from this :(

    EDIT: No, actually the reverb does hum, but not to the extent I find it too intrusive. It is adding the vib that induces the feedback...
     
    Last edited: Jan 25, 2019
  7. DennisM

    DennisM Tele-Meister

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    Have you checked your bias current?
     
  8. 7171551

    7171551 Tele-Afflicted

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    "Have you checked your bias current?"

    No. Only recently got this (second-hand) and I'm still in the honeymoon phase. I don't have the knowledge to work on it, it will have to go to a tech. Is it liable to be a big (eg "expensive") fix?
     
  9. 7171551

    7171551 Tele-Afflicted

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    "Have you checked your bias current?"

    No. Only recently got this (second-hand) and I'm still in the honeymoon phase. I don't have the knowledge to work on it, it will have to go to a tech. Is it liable to be a big (eg "expensive") fix?

    EDIT: Sorry for double post, due to site problems. Mods will hopefully delete it...
     
    Last edited: Jan 26, 2019
  10. Marc Morfei

    Marc Morfei Tele-Afflicted

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    No hum on mine.
     
  11. DennisM

    DennisM Tele-Meister

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    Not at all....if you have an honest tech it's a very fast and easy check/adjustment. Bias has a LOT to do with tremolo and possibly reverb.
     
    7171551 likes this.
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