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Help on a 465M

Discussion in 'General Electronics' started by Bill Brobeck, Oct 14, 2003.

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  1. Bill Brobeck

    Bill Brobeck Guest

    I recently bought a 465m for $50 for my son to play with. (I had an Eico
    when I was a kid.) The trace is not so good.I opened it up and found -3.0
    VDC on a TP that is supposed to be -5VDC. The +32 and +5 are OK. Looking at
    the various articles on the web and talking to a couple of people, including
    Deane Kidd, I concluded that

    1) I need a good manual for as little money as possible.
    2) Some advice based on your experiences as to which can is probably bad.
    3) I have the original instruction manual for a 564B. Is the instruction
    manual for the 465M just as comprehensive?

    Also I a little weary of really getting into it. I used to repair TV's when
    I was a kid, and got nailed one too many times, so a good manual is

    Any kind of advice, besides drop kicking it into the creek, would be
    appreciated. My son just got a 30 in 1 kit, sort of similar to the Allied
    Radio 100 in 1 kit I used to play with....but allot more IC minded...really
    cool stuff. I think it is important for him to see what happens to circuits
    over time...thats why I needed dual channels..

    Thanks in advance

    Bill Brobeck
  2. Don't be afraid to invest -- and I use that term deliberately --
    $50 or so for a good condition manual. The 465 and 475 series is some of
    the best hardware that Tektronix ever turned out.

    Manuals Plus has an operating/service manual for the 465M, in the
    form of a military tech manual reprint, for $55.00.

    HOWEVER -- Join, and check with, the gang on Yahoo's 'TekScopes'
    mailing list before you buy. They may be able to point you to a .pdf
    Could be anything, but electrolytic filter caps have been known to
    degrade over time. The ironic part about owning a 'scope is that you
    often need a working one to fix the bad one.
    Very much so. The 465 and 475 series was made well before
    Tektronix's manuals deteriorated into near-useless thicker-than-normal
    Troubleshooting test gear is not for the faint of heart. You would
    also do well to join the Tekscopes mailing list off of Yahoo groups.
    I've been a member for some time, and have gotten excellent advice for
    my own stuff.
    Anyone who even hints that you should drop-kick any such
    'classic' instrument anywhere is a good candidate for having the same
    treatment delivered to their own derriere.

    You've got a fine instrument there. Good luck with it.
  3. Dave Platt

    Dave Platt Guest

    Definitely worth having.

    Check with - the operating manual
    for the 465, and the service manual for the 465M are both available in
    electronic form (PDF scanned images of the paper originals, I assume).
    $9 if you FTP the manual, $12.85 if you want it on CD.
    Well, it's probably the filter can for the +5 rail! The manual will
    make it quite clear which one it is. If I recall correctly, most of
    the main filter caps are all in one small area of the main PCB - right
    rear as you look at the scope from front/above, I think.
    The service-and-operations manual for the 465 is very good indeed. I
    can't compare it to the 564B manual as I've never seen the latter.
    From what I have heard, the commonest problem with these 'scopes is
    that the filter capacitors for the DC supply rails simply fail due to
    old age - the water from the electrolyte diffuses out of the case, and
    the caps go high-ESR and cease to filter.

    I picked up a used-but-working 465 a couple of years ago for all of
    $25. It went belly-up about a year later, with the trace wobbling all
    over the place and the controls pretty much dead. DVM testing showed
    that one of the DC supplies had many volts of AC ripple on it... the
    filter cap had failed.

    Unfortunately, the original filter capacitors for the 465 are no
    longer being made, and the original supply of spares at Tek has run
    out. So, you probably won't be able to find an exact replacement.
    That's the bad news.

    The good news is that you'll almost certainly be able to pooge in a
    modern 'lytic, of equal or greater capacity and equal-or-higher WVDC
    rating. Buying high-temperature-rated caps wouldn't be a bad idea due
    to their proximity to the CRT.

    What I did was unsolder the existing cap can (+ and - tabs, and four
    (?) mounting tabs around the perimeter) and remove it. I bought a
    suitable replacement (somewhat smaller) at a local electronics store.
    The pins on the replacement didn't line up with the thru-holes in the
    PC board, so I cut/bent/soldered some long extension/adapter leads
    using 16-gauge solid copper wire, threaded the ends of the wires
    through the holes and then pulled them through (snaking the new can
    down to within about an inch of the PC board), cut the excess wires
    and soldered, and then glued the can to two of the adjacent original
    capacitor cans using some electronics-grade silicone sealant. Although
    the new can isn't actually fastened down to the PC board, the
    combination of the leads, and the adhesive holds it firmly in place
    without putting stress on anything.

    The 465 fired right up, and it works fine now. Well worth the couple
    of bucks, and the several hours it took to diagnose the problem and
    repair it.

    I've been advised that it's a good idea to power up scopes like this
    occasionally, just to make sure that the electrolytic caps do not
    de-form due to unuse.
  4. W7TI

    W7TI Guest


    So true. I used to be a production test tech on the 465/465B back in
    the '70s.

    Be aware though, that the 465/465B is a totally (and I mean totally)
    different design and construction from the 465M. The 'M was a military
    version which had essentially the same specs in terms of performance,
    but otherwise had almost nothing in common. Different case, boards, cal
    procedure, everything.

    My all time fave is the 465B. Snatch one up if you find a well cared
    for specimen. And when you open the case, look for my signature as
    Calibration Technician. :) I once figured that I had calibrated about
    one out of 50 that were ever made (about 1,000 out of roughly 50,000
    total production). At the time it was Tek's largest seller by far.

    Great scopes, all.
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