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Fisher 800-C on/off switch rebuild, replace.

Discussion in 'Fisher' started by ZenithNut, Jul 21, 2018.

  1. ZenithNut

    ZenithNut New Member

    Messages:
    24
    Hello all,
    I recently picked up a fairly clean stand alone Fisher 800-C in an original walnut cabinet. It appears the on off switch on the volume pot has been by passed. Its been altered to probably be turned on off with a power strip. Id like to repair the switch. What do you do to take it apart? I heard you could sand or remove any carbon build up from arcing.

    Thanks. Also where could i post a wanted ad? Id like to find some used tubes for my fisher 800c (x1 6gk5, x1 6aq8, x1 6hr6, x4 12ax7/ecc83, x4 7591A) they dont have to be high end 100% tubes, just some ok used ones to get the amp on its feet.
     
    Last edited: Jul 21, 2018

     

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  2. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

    Messages:
    2,717
    Location:
    Calgary, Alberta
    I believe you can buy new ones from Metalbone. Search Metalbone fisher kits and look on his site! ( switch anyway)
    For tubes contact Jim McShane (google)
     
  3. thornev

    thornev Active Member

    Messages:
    490
    Location:
    Mid Hudson Valley, NY
  4. ZenithNut

    ZenithNut New Member

    Messages:
    24
    Thanks for the responce. I know some of those tubes tend to get pricey so im hoping i can find someone with some ok ones for cheap ish to get a good feeling of where the amps at. I wouldnt mind knowing how to rebuild a on off pot but i might buy one as suggested.
     
  5. notdigital

    notdigital AK Subscriber Subscriber

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    2,237
    Location:
    NYNY
    Last edited: Jul 22, 2018
  6. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    You can access barter town ad forums by subscribing to AK. It's worth the $25, plus that's where all the crazy shiite:banana::confused: is! (Other sub-forums).Whole new world on AK when you can access it.
    Do you have tubes in it now? Except for the output tubes (7591's), they tend to last a long time. Both my 500c's have the originals but for one has different output tubes in it.
    Just curious. Good to see young blood getting into this hobby,too!
     
    Last edited: Jul 22, 2018
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  7. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    The power switches on a lot of old fisher gear tend to fail due to mechanical wear & the arcing csused by power surge when turned on. There's info in the fisher forums on the subject worth your time to check out.
    One of my 500c's had same problem, but there's nothing left of it to fix, so a wire nut connecting all 3 wires fixed that (for now). I use power strip to turn on/off if I'm going to use it. Best to do it this way, even if switch is in good shape, so as to keep it that way.
     
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  8. ZenithNut

    ZenithNut New Member

    Messages:
    24
    Thanks. Im trying to scrounge up the tubes i need to be able to fire it up which would be one more 6gk5, 6hr6, 6aq8 , four 12ax7, and four 7591A. The rest i have on hand. I got into vinyl and audio gear the same time i got into tube radios. All that was my senior year of hs. At 21 i now have an rca color ctc 25 sitting in my living room lol
     
  9. ZenithNut

    ZenithNut New Member

    Messages:
    24
    So even if the switch is good you recommend using a power strip to turn it on? While my 800C is not on its feet yet the pride of my fleet right now is a fisher 500-S driving some mach ones. (Yes a 500S with the 7189 power output tubes). Its a lovely amp
     
  10. ZenithNut

    ZenithNut New Member

    Messages:
    24
    So even if the switch is good you recommend using a power strip to turn it on? While my 800C is not on its feet yet the pride of my fleet right now is a fisher 500-S driving some mach ones. (Yes a 500S with the 7189 power output tubes). Its a lovely amp
     
  11. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,237
    Location:
    NYNY
    IF you replace/repair the switch AND you add a thermistor, the switch will be good for a good long time. The PRIMARY reason they fail is because of the arching. Essentially, lighting bolts fry the contacts inside to the point that they eventually break. With a thermistor, voltage to the receiver ramps up slowly eliminating sparks and prolonging the life of the switch. Any failure would be due to physical deterioration as opposed to that caused by arching.

    Many folk simply use a power strip to switch on/off their instrument. You can repair/replace the switch, or not, and still use a strip depending on your preference. Personally, I like to restore stuff as originally designed so I correct any switch issue, then use a bucking transformer which has a switch. But that's me.
     

     

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  12. ZenithNut

    ZenithNut New Member

    Messages:
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    It wouldnt hurt to put a thermistor on my 500-S power switch. What rated thermistor did you use? Id imagine you put it on the side with the ac coming in.
     
  13. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    Use a cl-80, it's most closely matched to the current draw of the 400/500/800series of fisher gear. As long as it's in line (series) with one power leg coming in, you're good. These little things get hot, so put it well away from any 'lytic caps & such. I'd use a terminal strip near the volume control if possible.
     
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  14. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    Location:
    New Jersey
    George ,
    That was nice work. Not that i have need but just out of curiosity , where did you get the donor switches for the parts for the rebuild?
    Also its been suggested other places to use a current limiter to help quell the surge some. Another alternative is to install a triac You need a working switch to start but it takes all the load off the switch.
     
  15. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,237
    Location:
    NYNY
    A bulk purchase a few years back when I picked up my X-202-B. The prior owner wired one of the slide switches as the power switch. That set up drove me nuts so I just hadda fix it. Over the years I've sold off most of my stock keeping only a few spares for that "just in case" moment.
     
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  16. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    Another potential source for tubes cheap but not reliable (think semi-rare garage sale/flea market score) is second-hand sales. My last good hit was a big tube caddy full of OLD radio tubes, most from ww2 & before, never-out-of-box, including rectifiers, 6L6's, 6v6's, 6d6, 6a7, 76,78 80, etc. Plus some newer ones. All n.o.s./o.e.m. I think I gave $40 or something for it. I literally have buckets of tubes acquired this way. Problem is, more people are getting wind of it, buying up whatever they can, thus driving up prices for all. Akron/canton craigslist now has a handful of these guys on there all the time.
    I may have a few of what you need, just have to find time to dig out & test. Will be in touch if I can help.
     
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  17. ZenithNut

    ZenithNut New Member

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    If you could find any id really appreciate it!
     
  18. AlTinkster92

    AlTinkster92 AK Subscriber Subscriber

    Messages:
    3,244
    Location:
    NC
    I have a new volume pot and switch on my 800C, has the CL soft start as well, still use a power strip to turn on and off. Any volume and switch from the 400, 500C as well as the 800C will work.
     
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  19. Catmanboo

    Catmanboo AK Subscriber Subscriber

    Messages:
    483
    Location:
    Atwater, ohio
    So did you acquire this thing missing tubes, or do you have some known duds in it? Your biggest $$ hit will be the 7591's. Best to choke on the cost & get a new, matched set. Those I know I don't have, I'm short a set myself. So the ones I do have, get moved around a bit, depending on what unit I'm going to use.
     
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  20. thornev

    thornev Active Member

    Messages:
    490
    Location:
    Mid Hudson Valley, NY
    I broke down for my 500-C and bought a quad set of Russian Tung-Sol 7591A's from TubeDepot and I'm very happy with them. I run them at about 80% of their rated max wattage which is supposed to be the sweet spot according to articles I've read and AK forum recommendations. Thorne
     
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