The Fisher Phono Preamp, and RIAA

Discussion in 'Fisher' started by dcgillespie, Jun 25, 2014.

  1. gadget73

    gadget73 junk junkie Subscriber

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  2. jonnyz123

    jonnyz123 New Member

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    Greetings more technical people (ahem @dcgillespie) . Thanks so much for this thread, and all the work that's been done. Wondering...for someone that will be asking someone else to perform a phono upgrade on my 500C, is there any sort of definitive To-Do List that I could hand them to simplify their research. While I'll be using someone who's competent in tube repairs, I doubt they would immediately have the insights that have been gathered here. I suppose they could read through this thread, but wondering if something more concise exists that takes into account a final consensus (+/- 20%) on how to best perform a phono upgrade, and a basic shopping list. Hope that's not asking too much, given the exhaustive info that's already been provided.

    Thanks again!
     
  3. gadget73

    gadget73 junk junkie Subscriber

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    well, basically the to-do list is you replace the phono PEC with one made up using the values dcgillespie posted. Thats all that needs to be done, and "need" here is pretty subjective. The stock circuit actually performs very well, the revision just gets it a little closer to ideal.
     
  4. larryderouin

    larryderouin You can be sure if it's Westinghouse??????? Subscriber

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    Concur with Gadget. All the new parts are really doing is bringing the RIAA back into "spec" and keeping a tighter leash on the reins with tighter tolerance parts. The RIAA circuit is common pretty much thru all FISHER gear. I've used the same parts on 400's, 800c's and a few different console preamps. The PEC (Packaged Electronic component) that FISHER used has a certain part # and it reigns pretty much thru all the late 50's and 1960's tube gear
     
  5. gadget73

    gadget73 junk junkie Subscriber

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    My rebuild was in a TA-600, same circuit as all the rest.
     
  6. CORYK

    CORYK AK Subscriber Subscriber

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    Would two 1megohm and one 130k resistors connected in series be ok for the 2.13 megohm resistor? Thanks.
     
  7. larryderouin

    larryderouin You can be sure if it's Westinghouse??????? Subscriber

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    As long as they measure to 2.13. You'd be better off with what you were answered on post 59 in this thread. (See page 3)
     
  8. gadget73

    gadget73 junk junkie Subscriber

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    that will work, sure. 2130000 ohms however you slice it. I used a 2.0M and a 130K just for spacing reasons.
     
  9. CORYK

    CORYK AK Subscriber Subscriber

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    Thanks Gadget
     
  10. CORYK

    CORYK AK Subscriber Subscriber

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    Does anyone have any results on the upgrade they would like to share? Thanks.
     

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