Fisher 500-B Restoration Process for The New Guy

Discussion in 'Fisher' started by Josey Wales, Nov 7, 2018.

  1. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
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    Wilmington, NC
    Josey,
    Its really handy to have your power tube bias adjustments above board vs inside the chassis.
    Here is what I did on my 500B:
    DSC01122.JPG DSC01124.JPG DSC01123.JPG

    Also if you look close you can see where I cut the can cap's when I re-stuffed them.
     
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  2. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Awesome! Did you see what 1rebmem did to his? Do you think i could do something like that?
     
  3. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Wow! That is awesome! And highly convenient! I'm going to need to look into that. Thanks!
     
  4. Josey Wales

    Josey Wales AK Subscriber Subscriber

    Messages:
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    Location:
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    I think i see it right a the beveled edge? How did you cut it so perfectly?
     
  5. 1rebmem

    1rebmem AK Subscriber Subscriber

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    Location:
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    I bought the pot's and test jacks on ebay. Then cut and bent the aluminum sheet metal just big enough to mount them.
    Search for some 10K trim pots designed for panel mount.
    The remaining components are on a board directly under and inside the chassis, the 500B has some open space there.

    I had the metal plate bent at work:)
    You could do pretty good with a bench vice.

    Matt's can cap bias assembly is a sweet setup though!!
     
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  6. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
    194
    Location:
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    The cap cans are cut right above the base flange.
    I just used a hack saw blade. The cans cut real easy.
    Some guys use an oscillating tool from what I read.
     
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  7. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
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    Location:
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    Josey........
    I bet you are seeing how this restoration/modification thing can grow. LOL
     
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  8. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
    194
    Location:
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    Since you are adding IBAM (which is a great thing to add) here is a schematic showing IBAM, along with some other mod's. The schematic is for a 500C but it is close enough to the 500B.
    I built the IBAM based on this schematic.
    Jef
     
  9. 1rebmem

    1rebmem AK Subscriber Subscriber

    Messages:
    194
    Location:
    Wilmington, NC
    ‎Josey,
    Here is a schematic for a 500C with IBAM and some other mods. The 500B is similar enough so I built my IBAM as shown in the schematic

    Edit: I can't figure out how to put the schematic here.
    It's in the AK Database.
     
    Last edited: Nov 13, 2018
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  10. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    I had no idea!! LOL.
     
  11. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Thank you, I will check that out. The amp came with an 800-C manual and schematic in the box. I'm wondering how different that is.
     

     

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  12. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    I'm definitely considering the can cap bias too! Oh, the choices! LOL!
     
  13. tcdriver

    tcdriver AK Subscriber Subscriber

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    Location:
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    The 7591As in question were purchased new in about 1985, installed in my 500-C which was used for a short time and then put in storage. They are reasonably fresh 1985 7591A tubes. They all test strong on the Hickok 6000 tube test and all show low grid 1 leakage.
     
    Last edited: Nov 13, 2018
  14. tcdriver

    tcdriver AK Subscriber Subscriber

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    Location:
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    Brilliant. I really like what you did mounting the test points and trim pots topside where they can easily be adjusted. :thumbsup:
     
  15. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Thank you! I'll find it i'm sure.
     
  16. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Location:
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    Does anyone have any advice on how not to become obsessed with this? I'm already brainstorming a whole vintage audio equipment testing restoration with Oscilloscope, Tube tester and a tube multimeter prior to my 500-B restoration. LOL.
     

     

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  17. tcdriver

    tcdriver AK Subscriber Subscriber

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    Nice work Matt. :thumbsup:
     
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  18. Josey Wales

    Josey Wales AK Subscriber Subscriber

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    Location:
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    This looks pretty great. I'm not sure which one to go with. This may sound like a dumb question but the can cap that was there, where did it go or does the IBAM replace the can cap? I know I sound stupid here. And enjoy Florida! Thanks.
     
  19. rufleruf

    rufleruf Poor Impulse Control Subscriber

    Messages:
    1,255
    I put a new electrolytic under the hood to replace the can.

    I *think* a replacement for the original cap could fit in there with the IBAM board - the new electrolytic is not that big.

    Regarding tube tester, oscilloscope etc, you could, but don't need to. I bought a pretty nice Hickok 752 a few years ago on bartertown here. Spent $250. Could probably double my money, and would have tested more than 1000 tubes in the process.

    As far as things getting out of control - yeah, for sure! I am starting restoration on a Tektronix 575 curvetracer to modify and use with my tube tester, and a Tektronix 502A for troublesooting, alignments etc. Tektronix stuff really scratches that "I should be working at NASA itch."

    I just need a Fisher 300 generator now and I'll be all tooled-up.
     
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  20. Tim D

    Tim D AK Subscriber Subscriber

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    Can you say "Rabbit Hole"?

    Welcome aboard!
     
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