Fisher TA-500 12ax7 Tubes

Discussion in 'Fisher' started by jgannon, Aug 11, 2017 at 5:53 PM.

  1. jgannon

    jgannon AK Subscriber Subscriber

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    I just have a very basic question. The Fisher TA-500 mono receiver has three 12ax7 tubes. If I am facing it, and looking down at it, there are two 12ax7's right behind the front grill of the receiver, and then one in the back with the three power tubes.

    I'm thinking that out of the two in the front, one of the 12ax7's is for the phono pre-amp, and another one for the tone amp. But I don't know which one is for which (or if I am even correct about that). And then there is the third tube in the back. What would that one be for?

    Thanks in advance!
     
  2. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    I don't have a FISHER Manual with the top layout so we'll use a SAMS' photofact.
    V8 (outer front) is the phono preamp.
    V9 (inner front) is the AF Amp
    V10(back next to output's) is split into the Driver and phase inverter.

    FISHER 500 Top Layout.jpg
     
  3. jgannon

    jgannon AK Subscriber Subscriber

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    Thanks Larry. But what does the AF stand for? Is that audio frequency? Is that what is considered the tone amp?
     
  4. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    AF = AUDIO FREQUENCY
    RF= RADIO FREQUENCY

    Af Amps are generally referred to as any amplifier stage other than phono stage. V9 would be the tone control section, while V10 is the Driver/Phase Inverter.
     
  5. jgannon

    jgannon AK Subscriber Subscriber

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    Ok, thanks Larry. And thanks for that SAMS pic.
     

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