Amp Voltages

Discussion in 'Amp Central Station' started by mike60510, Jan 10, 2019.

  1. D'tar

    D'tar Tele-Afflicted

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    Excellent! I would speculate that you assessed the entire circuit/components measuring actual values vs schematic values along with The shockbrothers equivalent to a Victoria Secret photo shoot!. I would be interested in anything you are willing to share. Much appreciated Wally.
     
  2. Wally

    Wally Telefied Ad Free Member

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    D’tar, I did not blueprint the amp. One must needs get paid for that kind of extra trouble. The amp sounded fantastic, so everything that I did not replace was stock....and did what it did.
    I have heard of one ‘blueprinting’ of a vintage Fender. Buddy Guy was particularly fond of how one of his 5F6A Bassman amps sounded, so he had Butler clone it. That entail a complete blueprinting of all components’ actual specs...not what say a resistor’s color code said but what the resistance actually was....same for caps...and trannies, I suppose. That is a clone....and that takes time.
    When an amp doesn’t sound as it should, I then get into that type of approach. I once owned a 1952 5B5 Pro that I resurrected. When I did the basic work, I replaced all of the paper-in-oil tone and coupling caps. Those do not hold up as do the later molded caps. I finally got all of the separate aspects done and reassembled the amp....field coil speaker amps make for fun, right? They have to be complete in cab before you can hear them. The amp did NOT sound good at all. So...I started checking the resistors. ALL of them had drifted substantially. Ex: 250K plate resistors measured around 470K. When I was through, the only original resistors in that amp were the input 68K’s that don’t see much current, right? When I fired it back up, it proved to be a magnificent amp. Someone must have played that amp a great deal....those resistors had witnessed some electrons passing through them.
     
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  3. D'tar

    D'tar Tele-Afflicted

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    I totally understand! We can glean quite a bit from the voltages themselves! Most likely no magic in a component that is 90% oos!
     
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  4. Wally

    Wally Telefied Ad Free Member

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    1957 5E3.....P= plate, K = cathode, S = screen grid. biasing...102% of mpd
    Heater voltage....6.58VAC

    V1--12AY7
    P1, P6--119vdc
    K3, K8--1.9vdc

    V2-12AX7
    P1--164.5vdc
    K3--1.14vdc
    P6--198.8vdc
    K8--17.3vdc

    V3--6V6
    P3--360vdc
    S4--329vdc
    K8--20.6vdc

    V4-6V6
    P3--358vdc
    S4--330vdc
    K8--20.6vdc

    V5-5Y3
    pin 4--361vac
    pin 6--363vac
    Pin 8--375vdc
     
    Last edited: Jan 11, 2019
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  5. D'tar

    D'tar Tele-Afflicted

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    @Wally

    I like those numbers... reminds me of my latest adventure in 5E3



    upload_2019-1-11_13-15-2.png
     
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