X-202 restoration

Discussion in 'Fisher' started by JEM@Clem, Dec 13, 2017.

  1. JEM@Clem

    JEM@Clem New Member

    Messages:
    10
    Location:
    Clemson, SC
    Your right gadget. Looking at the schematic 2 of the cans are common negative and one is common positive.
     
  2. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    33,946
    Location:
    Southern NJ
    The common positive is probably bias supply then. Usually lower voltage than the others as well. Just make sure you mind the polarity when rebuilding or replacing that one, it goes badly otherwise.
     
  3. JEM@Clem

    JEM@Clem New Member

    Messages:
    10
    Location:
    Clemson, SC
    Reading around the forum, it looks like the easiest modification I can make to help keep the tubes alive longer is putting a CL-80 current inrush limiter on the ac power supply, like Dave did in his "Gilding the X-202B" thread.
    When I put this in, it should go between the power switch and the ac in line, correct? And while I'm thinking about the power switch, the master volume potentiometer with the power switch built in appears to have kicked the bucket long ago. Any suggestions on where to find a new one?
     
  4. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,143
    Location:
    NYNY
    The primary purpose of the current limiter is to protect the on/off switch which is a historically proven weak spot across all fisher instruments. It slowly allows the ramp up of current from your wall to the unit. Secondarily, due to resistance, it drops the voltage to the unit slightly which helps it "see" voltage that is closer to what the designers were exposed to back in the day. The CL-80 only indirectly helps affect tube longevity and only to a negligible degree.

    If you look at Dave's restoration in his "gilded" version, he put it on an existing terminal strip. I put mine in at a different location. When all is said and done, it does go "between" the AC line and the switch but where in that circuit would depend on you. I chose the location in mine because I flipped resistors on the terminal strip where Dave put his CL-80 so there wasn't room, and the spot that I eventually chose had vent holes above. In the end it depends on your own design eye.

    As far as the power switch is concerned, I may be able to help you but that conversation would have to take place privately.

    [​IMG]
     
  5. JEM@Clem

    JEM@Clem New Member

    Messages:
    10
    Location:
    Clemson, SC
    Currently I'm looking at replacing all the electrolytic caps and adding a current inrush limiter. here's my parts list:
    1. original: 50uF@3V
      1. replacement: 50uF@6V
    2. 40@500
      1. 40@600
    3. 20@250
      1. 22@350
    4. 40@450
      1. 40@450
    5. 40@400
      1. 40@450
    6. 20@300
      1. 22@350
    7. 20@250
      1. 22@350
    8. 1000@35
      1. 1000@35
    9. 50@70
      1. 50@100
    one that i'm unsure about is replacing my cardboard covered cap can (200uF@250V) with one of equal value, but labeled 250VAC (https://www.amazon.com/TOOGOO-200MFD-Terminal-Starting-Capacitor/dp/B00SUXOAT6)
    I think the original voltages were given in DC voltage, so this part shouldn't work. If this won't work, where can I look for one that will?
     
  6. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    9,042
    Location:
    Ball Ground, GA
    One option is to get this can from Antique Electronic Supply: www.tubesandmore.com/products/capacitor-ce-mfg-350v-50505050uf

    Strap all four sections together making it a 200 uF cap at 350 vdc. Remove the cardboard cover from the old cap, and install it over the new cap using an appropriate adhesive to secure it.

    I hope this helps!

    Dave
     
  7. JEM@Clem

    JEM@Clem New Member

    Messages:
    10
    Location:
    Clemson, SC
    I finally got parts in, and now I'm wondering how to get the cardboard off of the cap
     
  8. JEM@Clem

    JEM@Clem New Member

    Messages:
    10
    Location:
    Clemson, SC
    Also I found an inconsistency between the parts list and the schematic. 20uf vs. 200uf
    parts list.PNG
    schematic.PNG
    Guess who bought the wrong one.
     
  9. gadget73

    gadget73 junk junkie Subscriber

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    Location:
    Southern NJ
    I go by whats in the unit vs what the schematic says when possible.
     
  10. nj pheonix

    nj pheonix AK Subscriber Subscriber

    Messages:
    8,421
    Location:
    New Jersey
    If it makes you feel any better, we've all ordered the wrong thing one time or another.
     
  11. Catmanboo

    Catmanboo Member

    Messages:
    63
    Location:
    Atwater, ohio
    Try a hair drier to get the sleeve off. Heat should soften the adhesive, usually a dab of tar or some such. Twist gently.
    Had to do this once to get info stamped on the can. Ya'd think they would've marked the cardboard sleeve, but-noooo! And schematics sometimes have typo's & other discrepancies. If it says something other than what's on the part at hand, provided it's an oem part, go with what the part says.
     
  12. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    33,946
    Location:
    Southern NJ
    I've always ordered the right part, just sometimes its for the wrong project and it takes years to obtain the correct one :) Took me almost 10 years to buy the Continental to make use of the antenna mast I'd bought. Also possible I bought it to make use of the AC evaporator core I bought like 4 years ago. I hope it is, I don't feel like having to buy something to install that in.
     
    nj pheonix likes this.

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