Fisher 400-T score

Discussion in 'Fisher' started by rossm, Sep 17, 2017.

  1. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    21,694
    Location:
    Glen Burnie Md.
    Thanks Fred. I had forgot that part. I finally figured out what rossm was asking with regard to the clips on the pins. The clips on the peripheral pin do lift straight up. Make sure you diagram it with pin #'s and wire color, AND TAKE PICTURES! These will be your greatest help getting the leads back on the correct pins.
     

     

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  2. rossm

    rossm AK Subscriber Subscriber

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    Thanks guys, I got some free time tonight and felt brave so I took lots of pics and found out how easy it was to remove the clips off the posts. This is my first Fisher and have never encountered this setup. I must admit its pretty slick way of connecting the boards, must have been expensive and time consuming to crimp all the connectors. Anyway I got all the connectors removed and took the board off the plastic standoffs. Had 2 of the standoffs crumble into dust, maybe I can adapt some of the old computer motherboard standoffs I have laying around to work. Now I can see what you were talking about larryderouin ! the third connector on the large caps are just for mounting, I have never seen this. Well I am off to mouser to order new caps, might as well change em all out while I have the board out.
    I will be back and let you know how the power supply turns out..
     
  3. rossm

    rossm AK Subscriber Subscriber

    Messages:
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    Having a hard time at Mouser/Digikey finding a 70v 500mfd axial mount cap, any thing else that might work ?
    fisher.png
     
  4. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,694
    Location:
    Glen Burnie Md.
    470uf 80v, 560uf 80v, 560uf 100v. I'd be more inclined to use the 560uf. If you can't find anything in an axial, use a radial. Mount it so the POS side is as close to the mounting hole as possible and still have lead for the neg in the hole and solderable.
     
  5. rossm

    rossm AK Subscriber Subscriber

    Messages:
    236
    Hi again!!
    I finally got around to finishing up this receiver. I have replaced the electrolytic caps on power supply and amp board. Everything except for am seems to be working fine. Looking at the service manual I attempted to do the “power amplifier center voltage test” the spec is +- 100mv , I am measuring 206mv left and 186mv right, but the sm doesn’t say anything about how to adjust it ???
    I did get the idle current to spec at 15mv
    I have also noticed the heat sinks get pretty toasty at volume
    E9D98139-D3C5-461D-B160-21630BA7F7A9.jpeg
    Amazing how much smaller the caps are
     
  6. fred soop

    fred soop Super Member

    Messages:
    1,943
    Center voltage is only critical at absolute peak power. If it is slightly off (a couple of volts), it only means that the headroom for positive and negative peaks is not the same. If there is no adjustment, then the power amp input transistor differential pair may not be matched.
     

     

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  7. rossm

    rossm AK Subscriber Subscriber

    Messages:
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    Thanks for the info on that. I have buttoned it up and it’s in the rack now. It’s connected to a pair of advent 2002 speakers and it sounds amazing ! I am very impressed with this almost 50 year old receiver. It’s gonna be a keeper
     

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