6505+ Problems.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by kc_hubbs, May 18, 2015.

  1. kc_hubbs

    kc_hubbs Member

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    This morning i go to play the amp, and when i switched on the effects loop, i lost a ton of volume. I put brand new cables on everything in my loop just a few days ago.

    So, then i take a few different new patch cable out of the box and just connect the input to output, and i still get the same results. If i take the cable out of the loop and leave it open, I still get the volume loss.

    If i turn the loop off on the footswitch, I get all my volume back.




    2nd problem:

    In the past 3 months the amp occasionally makes really weird noises. It only done it like 3 times in 3 months. Its like i will be playing, and all of a sudden their is a high pitched squeal in the background, and if you play guitar during these moments, it sounds almost like a bass. Even your high e string sounds like a bass being played.
     
  2. Markorock37

    Markorock37 Member

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    I would start with tube V3, should be second tube from the power tubes. That is the driver and recovery stage for the effects loop.
     
  3. RussB

    RussB low rent hobbyist Silver Supporting Member

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    [​IMG]


    5150II/6505+ Signal Path

    clean and crunch channels

    guitar > V1 (one half) > V6 > V3 > V4 > Power Tubes

    lead channel

    guitar > V1 > V2 > V5 > V3 > V4 > Power Tubes

    V3 is for the loop
    V4 is the PI
     
  4. kc_hubbs

    kc_hubbs Member

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    I forgot to mention something earlier. Since the effects loop problem started, the head has been re-tubed 2 times. I will still check the tubes though. I have a bunch of working pre-amp tubes laying around.
     
  5. RussB

    RussB low rent hobbyist Silver Supporting Member

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  6. Washburnmemphis

    Washburnmemphis Member

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    Are you able to try a different footswitch?
     
  7. kc_hubbs

    kc_hubbs Member

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    Ill try the de-ox-it.

    I only have the one footswitch. So i cant try another one.

    Are you guys thinking these 2 problems are related, or are you all just talking about the effects loop problem ?
     
  8. CDA

    CDA Indigenous Donkey

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    Many of these amps have their cathode bypass caps installed backwards. Like all of them. I see issues like you are talking about regularly and I just rebuild the preamp board and my guys are good to go. It's a good time to upgrade all the ****** little plate loads and cathode resistors too. If you go with film caps instead of electrolytics you'll lower the noise floor quite a bit as well.
     
  9. RussB

    RussB low rent hobbyist Silver Supporting Member

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    Very interesting!


    I had went through my son's 5150II and replaced (upgraded?) many components, including the cathode bypass caps, and used metal film caps for many. We did indeed notice a significantly lower noise floor
     

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