Tube Dreamer Awakened: Fisher X-100 3

Discussion in 'Fisher' started by Man in Cave, Aug 26, 2017.

  1. macgolf

    macgolf "overcome by art" Subscriber

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    Location:
    Central IL
    That is a nice clean chassis. I would like to find what looks like a RCA black plate 12AX7 (far left in 2nd to last picture) to run in my V3 position. Liking the RCA 7025 I'm running now though. If balanced, that might be one to try in your V3(center position of the 5 front tubes). Still learning myself so can't comment on the undersides. Glad you're enjoying it.
     
  2. Man in Cave

    Man in Cave The Tube Dreamer Is Awake Subscriber

    I didn't notice the visual difference until you pointed it out. The only lettering left on that black-plated tube is the "12AX7" From the tube schematic it reads V3 as the Tone Control Amplifiers. It's brighter than the others meaning there's more of a chassis reflection coming off it. I can try your suggestion. It'd be my first venture into "tube rolling." V4 tube reads, "Great Britain". Vs 3, 2, 1 tubes read "West Germany", so those are maybe the originals.

    S.J.
     
  3. larryderouin

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

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    I would change the 2 black output coupling caps. The other two (EROFOL's) are most likely OK. If you can find 2 more EROFOLS of at least 400v in the value on the caps, put them in. Otherwise, caps of your choice for all 4, and save the EROFOL's for another position that uses that value/voltage (or a lower voltage.) The Black Beauty between the Main filter caps should BE REPLACED. It's NOT a death cap. But still should be replaced. The ones circled in RED are must replace in yellow are the EROFOLS.
    x-100-3 underside modded.JPG

    While it's running, check the temps of the Main Filter CAN CAPS. If after 15 minutes they feel hotter than the surrounding transformers/tubes/components Replace them. You'll have some spot heating from the tubes and transformers, so check in multiple spots on the CAN. If replacements are needed, you can cut them open, yank out the guts and replace the guts with individual caps (105*C recommended). If you feel that it's above your skill set, Hayseed Hamfest can custom make the set. Talk to TOM about it. He'll need the info from the Service Manual and the actual can's.

    C3B is listed on the parts list as a 200uf @ 70v, but on the schematic it's listed as a 70UF. Check the CAN and verify the UF and Voltage on both sections. I would think it's a 200uf @ 70V. A 220uf/100V would be the modern equivalent replacement. Note: There is a good amount of room to add some terminal strips and then replace the Main Filter CAN sections with Separate Caps underneath, keeping the cans' for aesthetic and safety reasons.
     
    Last edited: Aug 31, 2017
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  4. Man in Cave

    Man in Cave The Tube Dreamer Is Awake Subscriber

    Thanks so much for all the suggestions. I've never done replacing caps before, however, it's time to learn. I'll see about ordering what you've suggested as soon as I'm able. After the dust cleaning last night a ran it for one record and the big main filter caps did not run hot. They stayed cool to the touch except the tube sides. The black cardboard one does look a little rough.

    S.J.
     
  5. macgolf

    macgolf "overcome by art" Subscriber

    Messages:
    696
    Location:
    Central IL
    Interesting, as my unit came to me with a 12AX7A in the V4( one of the phase inverter) position. After some cleaning, I put it into the V3 and kept the 4 original Fishers matched as pairs in the other 4 front end positions. I could only see slight traces of red paint on that tube with no other markings other than the tube number. Thanks to some excellent threads here, I replaced the originals in V4 & V5 with EH 12AX7's for less than the replacement cost of 1 of the originals. Didn't miss a beat with that change and left me with another pair of nice originals if needed. Haven't felt the need to go with anything other than the originals in the V1 & V2 (phono and tape preamp) tubes. No Fisher labeling on my 7189's, just a few small numbers here and there.
     
  6. larryderouin

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

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    You both might want to read Dave's post about the noose in the phase inverter position on the 400. Russian tubes aren't really good here, in the stock 400 or with the noose removed. He recommends old stock tubes (tele's, mullard, rca, ge sylvania, etc.) in the phase inverter. I'm not sure how much the noose is in the x-100 series, but it's probably not as bad as the 400. http://audiokarma.org/forums/index.php?threads/fisher-400-service-bulletin.671281/ This also may or may not apply to the X100 series amp.
     
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