Mod Gone Wrong?

Discussion in 'The Workbench' started by Neddi, Jun 16, 2019.

  1. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Thanks Brad. I’m not confident on the TMB with the loop between the MV & PI but I will be experimenting as I will look at it 360* on a Jose pre TS MV Dual gain build.

    I believe R1 (2.2meg r) on the Metro Loop needs reduced to a 390k to allow for proper signal to noise /clipping. I have to check my old notes.
     
    Last edited: Jul 6, 2019
  2. fifteenohms

    fifteenohms Well-Known Member

    Joined:
    Sep 30, 2010
    Messages:
    1,071
    Likes Received:
    537
    Location:
    Los Angeles, CA
    Not true at all: the entire amp was an effect loop.

    I had one of his 20 or so jmp100's modded by Bradshaw racked as power amp servers.

    My 78 had all the work done, then bypassed into power amp input, then returned to mod-stock except for the added DI.
     
  3. fifteenohms

    fifteenohms Well-Known Member

    Joined:
    Sep 30, 2010
    Messages:
    1,071
    Likes Received:
    537
    Location:
    Los Angeles, CA
    Wow I really enjoyed this thread but it gave me a headache wondering about parties involved.

    Then I saw the video, and it has some reasonable whump to it but I cant turn it up as loud as Id like right now to tell.

    But it looks good! I hope that original FX loop issue was clarified.
     
  4. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,492
    Likes Received:
    9,829
    Location:
    US of A
    If it is racked as a power amplifier then its not an intergrated musical amplifier with effects loop.
    Do you mind elaborating if that is not the case?
     
  5. fifteenohms

    fifteenohms Well-Known Member

    Joined:
    Sep 30, 2010
    Messages:
    1,071
    Likes Received:
    537
    Location:
    Los Angeles, CA
    Google it. It got stolen and I am not fond of the thought but theres plenty of pix out there, and probably as much guesswork as to what was in them.

    The pics you want are four heads high cases, five or six like that.

    They began turning up through Recycler from 92-on and mine was owned by that Chili Pepper guy. I paid $275.00
     
  6. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,492
    Likes Received:
    9,829
    Location:
    US of A
    Nah. My first sentence stated enough.
     
  7. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Thanks for the well wishes.

    The original Metro Loop appeared to have intermittent issues. I did not take time to isolate as there was much to do. The replacement Metro Loop had a over heated trace pad which was easily identifiable so I jumped it. There were other issues as stated before but all has been addressed & resolved.

    David
     
    Last edited: Jul 4, 2019
    mAx___ likes this.
  8. Guitar-Rocker

    Guitar-Rocker Well-Known Member

    Joined:
    Mar 5, 2012
    Messages:
    2,741
    Likes Received:
    2,324
    Location:
    Indianapolis, Indiana
    What an end run around, to get it back together again. Kudos on the re-straightening job David.
     
    CoyotesGator, NewReligion and neikeel like this.
  9. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Thank you Sir.

    Preface: My Oscilloscope crashed last month.

    This is Revision II of the rebuild. A perfect example of why High Gain builders should allow the amps to burn for a few hours to allow the resistors to settle and flow all of the capacitors. After just a couple hours the amp started to oscillate or so I thought. I let it continue and yes, sure enough there was an issue.

    It is only the 3rd time I had an issue like this out of near triple digits. It has always been with a Small Box Chassis. Confined quarters with the Metropoulos Zero Loss Effects Loop.

    The Resolution? I moved the Loop 1.5" away from the VX (First Gain stage) after addressing lead dress possibilities and measuring components values out of circuit and voltages in circuit.

    It was a simple correction. The amp now has a fixed resonance as the resonance on a 1 Meg Pot was just too close to the loop on either side & did not function correctly as it is part of the NFB output section.

    Below is a short audio sample.

    David...♫


    Revision II
    [​IMG]
     
    Last edited: Jul 6, 2019
    CoyotesGator likes this.
  10. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Neddi Pandora Revision II Video by David Hopkins...♫

    For Clarification:

    When I say I moved the “board” I meant the Metro Zero Loss Loop Board. As it was causing issue covering the added VX tube (extra 4th stage) part of the mod of the Input Circuit.

     
    Last edited: Jul 8, 2019
  11. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,492
    Likes Received:
    9,829
    Location:
    US of A
    Sounds heavy and articulate. Good one David.
     
    NewReligion likes this.
  12. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Thank you Mickey.

    David
     
  13. CoyotesGator

    CoyotesGator Well-Known Member

    Joined:
    Jul 31, 2012
    Messages:
    1,818
    Likes Received:
    1,529
    Location:
    The Institute for the Very, Very, Very Nervous
    Well done!
     
    NewReligion likes this.
  14. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Thank you.
     
  15. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    I called Neddi over the weekend to notify him that the amp is ready when he is. He stated he was away over the weekend and would make arrangements Monday...ish.

    David
     
    mickeydg5 likes this.
  16. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,492
    Likes Received:
    9,829
    Location:
    US of A
    Great!
    Waiting on NFB.
     
  17. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Let’s hope not.
     
    mAx___ likes this.
  18. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,492
    Likes Received:
    9,829
    Location:
    US of A
    NFB
    Neddi feedback.
    Gotcha! :)
     
    mAx___ and NewReligion like this.
  19. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    lol...♫
     
    Last edited: Jul 9, 2019
  20. NewReligion

    NewReligion Well-Known Member VIP Member

    Joined:
    Nov 17, 2009
    Messages:
    10,976
    Likes Received:
    7,796
    Location:
    Paradise
    Neddi's JMP 2204 Pandora Shipped out today by FedEx.

    David...♫
     
    mAx___ likes this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice