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tektronix 465 question

Discussion in 'Electronic Equipment' started by keithcc, May 30, 2005.

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  1. keithcc

    keithcc Guest

    I just bought a tek 465 scope on ebay, but am having a problem with it.
    For about half the time, everything works fine, but occasionally, and
    for no apparent reason, the scope will behave as if there is no
    incoming signal on either channel - time/div, horizontal position,
    intensity, etc can be changed, but vertical position cannot be, and
    nothing will display on the crt when a signal is applied to either
    channel. During such periods, setting A Trigger Source to a channel and
    then pressing the trig view button correctly displays the signal on
    that channel. Furthermore, and perhaps irrelevantly, the AC/GND/DC
    selector below CH 1's volts/div knob doesn't click like CH 2's
    does.
    The problem seems like it might be minor - a loose connection somewhere
    - since at times the scope functions exactly as it should. any
    suggestions as to what could be wrong are very much appreciated - i
    don't have much experience with scopes, and certianly not with
    troubleshooting them. I also don't have a service manual yet, but am
    trying to find one on ebay. Thanks.
     
  2. Jim Yanik

    Jim Yanik Guest

    You may have lost a roller bearing on the AC/DC/GND switch,or the lever has
    loosened on the switch shaft.
    Maybe a bad trigger view/BW limit switch on the vertical pre-amp board.It's
    towards the rear of the PCB,near the delay line connection.It's heat-staked
    on,and has HF cam switch contacts that have a very low wiping force,and are
    suceptible to contamination,like films from plastics outgassing,cig
    smoke,dirt.

    At TEK,we used to remove the plastic sw.frame,tear off the old
    contacts,bolt on new ones from a repair kit,and stake on a new
    sw.frame.Those parts are no longer available.

    So,what you do is take a narrow strip of paper,slide it under a closed
    contact,and put a drop of 90% isopropyl alcohol on the paper,and carefully
    slide it back and forth to clean the contact and the PCB pad.If the
    contacts have lost tension,then you have to scavenge some from a parts
    board.
     
  3. tekamn

    tekamn Guest

    do as Jim proposed: Clean the contacts and of course the rest of the
    o'scope (cause iif it's put away the housing, that's easy to do in one
    action).

    and chck for bad caps in the LV supply -- electrolytics easily get
    dried out in these scopes during the years.

    After doing this maintenance, the scope should still work when used
    occasionally when you will be long gone. The 465 are realy nice and
    affordable nowadays.

    hth,
    Andreas
     
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