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465M numerous problems

Discussion in 'Electronic Repair' started by Gavin, May 19, 2007.

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  1. Gavin

    Gavin Guest

    Hello all,

    I currently have on hand a tektronix 465M(military version) that has
    numerous issues:

    1. Power supply problem, The green power own led blinks and according
    to the manual it says low line voltage
    (I have checked the power supplies +32, +5, -5 all check out okay,
    possible faulty detection circuit?)

    2. problem with the delay time pos pot. doesnt seem to work.
    (working on currently)

    3. beam shape when beamfinder/trace is displayed, it looks like a oval/
    blur no matter how much the controls are adjusted and maybe the CRT is
    out of alignment?

    Did any of you have similar issues with this model. Also would this
    even be economical to repair considering the amount of problems or are
    these usually easy fixes. Or should i use this to anchor a boat.
    Opinions/ help on problems 1 and 3 would be greatly appreciated.
    Thanks guys.
  2. w9gb

    w9gb Guest

    "I have checked the power supplies +32, +5, -5 all check out okay,
    possible faulty detection circuit?"

    Not that I doubt your work, but if you just used a VOM/DVM -- that says
    nothing about its proper rectification and filtering.
    First, have very good lighting and a magnifying glass (and a very
    discriminating eyesight). Why?
    Once found a resistor with a very small crack -- tested okay (correct
    resistance) cold -- but then when equipment operated just enough heating
    caused it to go open.

    Electrolytic capacitors, due to the age (and potential field abuse -
    military, etc.), I examine extremely closely with "old boatanchor" test and
    radio equipment. Often if I find one or 2 that are questionable -- for my
    equipment -- I replace them all (preventative for further service bench

  3. Gavin

    Gavin Guest

    thanks. ill go look at that. i must have had a brain fart forgetting
    to check the capacitors first. Oh i had one more question, is it
    normal for the board to be.....errr sticky?
  4. Guest

    use an ESR meter on the caps!

  5. Jim Yanik

    Jim Yanik Guest

    That could be electrolytics LEAKING onto the PCB.
    That stuff WILL eat thru PCB traces.

    also,where you test supplies,you should use a Variac to lower/raise the AC
    line voltage to see if the supplies still regulate at the low and high ends
    of the specified input range.
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