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Tek 465M vert problem

Discussion in 'Electronic Repair' started by cajuncalibration, Aug 5, 2005.

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  1. I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
    display shrinks about .4 div from the correct calibrated position. I
    thought dirty contacts, I pulled the assembly completely apart and
    cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
    shape, and there visually isn't anything wrong. However, I still have
    the same problem. Now that I look back, is it a possibility that the
    black rod that switches the reeds has gotten worn? I was just
    wondering if anyone had this problem before, and if that was a
    possibility. Everything on the scope works fine, and if you turn the
    knob to the extremes of the detent, it works fine. Sorry for the
    vagueness, I just wanted some advise before I tear it apart again.

    Thanks,
    Steve
     
  2. Jim Yanik

    Jim Yanik Guest

    cajuncalibration wrote in
    Cam drum
    Not really.
    It's more of a loss of spring tension in the spring contacts.
    These HF cam switch contacts have a very low wiping force.
    Also,outgassing from plastic parts may have left a hard film on the PCB
    contacts,a light cleaning with a pencil eraser will help there.
    Don't go so hard you remove the gold plating.
    It's a common problem.
     
  3. Jim Yanik

    Jim Yanik Guest

    cajuncalibration wrote in
    Due to the very low wiping force of the HF contacts,and effects of solvents
    on plastics.

    If the atten PCB is translucent,it's polystyrene,melts easily,and most
    solvents affect it.(microcracks)
    Some atten PCBs were ordinary epoxy-glass,I don't recall about the 465M.
    The similar 455 atten PCBs were epoxy-glass.
     
  4. I used a pink eraser on the contacts, maybe I didn't do a through
    enough job. I guess I can pull it back apart, maybe get lucky this
    time.

    Also, just out of curiousity, what kind of material is the board made
    out of? Also, I've read many times not to use any cleaners that leave
    residue, not to clean anything but the contacts, not to breathe on the
    vertical attenuators etc. etc., is this just due to the extreme
    sensitivity of the components?

    Thanks for the reply,
    Steve
     
  5. Problem fixed, thanks for the reply. I cleaned the contacts very well
    again, but it still had the same problem, so i lightly pushed on the
    tops of the contacts w/ a paper stick until I found the two that were
    the problems, and just slightly tweaked the contacts back down. It
    works perfect now. The board is translucent, which is what made me
    wonder. It didn't seem like typical epoxy-glass board. Thanks for
    the reply again, and now I finally have a fully functional scope that
    I bought on ebay for a buck plus s&h (I have 4 scopes, all bad in one
    way or another).

    Thanks,
    Steve
     
  6. Chris Jones

    Chris Jones Guest

    I'm glad to hear that you fixed it.
    I had a similar problem with a 475, and it was a poor contact on one of the
    little attenuator modules which plug into the attenuator PCB if I remember
    correctly. I had to unplug and reinsert the attenuators to fix it.

    Chris
     
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