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HP8116A *almost* working perfectly

Discussion in 'Electronic Repair' started by JW, Aug 17, 2007.

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  1. JW

    JW Guest

    Hello all,

    I have this HP 8116A 50MHz Programmable pulse/function generator that's
    almost working perfectly. However, whenever the amplitude is set below
    EXACTLY 10.00 volts, the output puts out nothing. 9.99 volts and lower
    does not work at all. Any ideas?

    Thanks!
     
  2. N Cook

    N Cook Guest

    Different make but the symptoms surprisingly the same and rang a bell, nasty
    to work on IIRC

    Philips PM5770 pulse generator
    Output on 10V setting but not lower settings.
    Inside the screened attenuator box a secondary switch
    mechanism comes into action in the 10Volt position
    but was failing to return on spring action on lower settings.

    from my repair briefs file
    http://www.divdev.fsnet.co.uk/repair4.htm
     

  3. Do you have the manual?

    <http://www.home.agilent.com/agilent...=615544&lc=eng&cc=US&nfr=-536900193.536900597>


    Some of the programmable generators use relays to switch pads in and
    out, to set the output level. They fail, from heavy usage. I had most
    of them go bad in an old HP 3325B over a couple year period of daily
    use.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  4. Chris Jones

    Chris Jones Guest

    Does it have a switchable output attenuator that should switch at that
    level? I would look for something like that.

    Chris
     
  5. JW

    JW Guest

    Yup. Got it, but no schematics on that one...
    Thanks! That gave me the clue I needed. I found a number of reed relays
    and 'scoping out their coil inputs while switching between 9.99 and 10.00
    volts noticed that one of them was only getting down to about 2 volts.
    Traced it back to a 74LS374 octal latch - it's pin 9 output was bad. The
    chip is located on the bottom board of the 3 stacked boards in the unit.
    The chip is located on the right side near the front panel when the unit
    is oriented facing you.

    Thanks again, Michael. And thanks to N Cook and Chris as well!
     

  6. You're welcome.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
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