fisher MPX decoder troubleshoot

Discussion in 'Fisher' started by vintelectra, Apr 21, 2013.

  1. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    35,177
    Location:
    Southern NJ
    I tried to avoid using the second filter cap after the drop resistor once, it did not work correctly. I presume this is why. Adding the cap back in made it work properly again.
     

     

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  2. vintelectra

    vintelectra Active Member

    Messages:
    450
    Thank you.That should be the reason! I have converted an old Collins power supply to operate these mpx ( for fun) with voltage reduction netwoks for mpx 65 and WX.
    I added a 40 uf elecrol filter at the output of 165 v ,& did the tric. May be too high capacitance? Will try lower,
    What I find interesting is that the 275 v output does not have a ripple, while the165 V does, although both come from the same Collins PS terminal .
     
  3. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    35,177
    Location:
    Southern NJ
    I don't know that the value of that cap after the drop resistor is all that critical. It just needs to be big enough to decouple anything from the first voltage stage.
     
  4. vintelectra

    vintelectra Active Member

    Messages:
    450
    You are right, I tinkered with different caps with no change , I will settle for a 40 uf. Finish calibration of mpx 65 with max separation 37 dB. Now I will test the new box adaptor with a WX mpx Thanks for insight and help. martin
     

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