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Tektronix 466 Scope Problem

Discussion in 'Electronic Repair' started by Chris, Nov 10, 2003.

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  1. Chris

    Chris Guest

    Hi guys. I'm hoping that some of the more Electronics oriented
    individuals out there may be able to help me. I am pretty much self
    taught when it comes to electronics so my knowledge is very limited. I
    always try my very best to troubleshoot and fix things when I have a
    problem and believe it or not, I'm successful about 90% of the time.
    Mainly it's because I can see the "burned" part or "hair line"
    fracture in the solder board.

    Well my Tektronix scope was something I purchased from e-bay about 2
    years ago. It worked perfectly from what I could tell. I was very new
    to scopes and didn't have any experience running them. My friend came
    over one day and was like "oh yeah I can show you how to run a
    scope... bla bla."

    To make a long story short during a calibration discussion he
    suggested we simply test the AC "house current" for the 60 cycles per
    second that it should be. I don't remember exactly how we connected
    the probes to the AC but when I made the final connection the circuit
    breaker popped and I looked at him with a rather "Pissed off"

    I was sure my scope was ruined. I reset the breaker and turned the
    scope on. It worked fine ..."See it's ok" my friend said! About 10 or
    15 seconds later my scope went into a rather "dead" state. -Needless
    to say I was pissed. I take pride in all of my equipment matter
    how old it is. I take good care of it and try to learn as much as I
    can with what I have.

    We checked the fuses and they were both fine in the scope. He then
    said ..."I'll take it to work dude. My buddy Hank at work fixes these
    things all day long. He'll have it up and running in under 10 minutes
    I bet." Needless to say about 4 months later I got it back ...still
    broken. All Hank told my friend was something about the DC power
    supply? I assume that means that one of the full wave bridge
    rectifiers is bad? -But if that's the case why didn't he find which
    one and replace it?

    Anyway, from what I can tell, by turning the scope on for several
    seconds here is what DOES come on: The lights on the front light up.
    The trace dots do come up after a few seconds on the screen, but they
    do not move. They get so bright (maybe because they are not moving?)
    that I turn the scope off quickly in fear of it burning something
    further out.

    The fan on the back DOES NOT run anymore and the time portion does not
    appear to work since I see only 1 bright or 2 bright dots in the
    center (I think it's 2 of them).

    I am willing to try or test anything you can suggest to help me fix
    this. Please help if you can :)

    Thank You,
  2. James Sweet

    James Sweet Guest

    Sounds like one output of the power supply is dead, you'll need to do some
    testing, do you have a multimeter? Turn the brightness way down, the static
    dot will burn into the tube quickly.
  3. Chris

    Chris Guest


    I have started to test the transformer and it appears to be good. I
    have 5 labeled pins on the transformer (10 - 14) and they all measure
    resistance so I assume the windings are all intact. I started
    measuring with my multi-meter by connecting my negative probe to the
    ground and then testing various points with the positive probe, while
    the power was on to my scope. Everything appears normal from the few
    things I have tested, except for the 1 full wave bridge rectifier. It
    is getting some strange readings. Maybe this is the problem or maybe
    the capacitor that it's connected to is the problem? I would love to
    check some values against anyone with another 466 scope. Can I ask for
    some assistance in that area please guys?

    If you have a TEK 466 storage scope, please let me know and I'll tell
    you which rectifier measured oddly and how I got the measurement.

    Are there any repair manuals with these that I can download or order?
    I would like to know if there is some simple standard tests to try to
    pinpoint my problem. I am very new to troubleshooting electronics like
    this but I'm willing to learn :)

    The DOT is off to the side far enough that it is not visible. I have
    tried to center it to see the dot but can not, I played with the "Find
    Beam" and that does center it, but I only dare to hit the button for a
    moment, as I don't want to burn my screen. I have turned it down as
    far as I can so I just don't keep the scope turned on very long while
    I'm testing. I hope I am not hurting it during my short tests.

    I'm looking for any help you guys can offer. I can not afford to send
    it in for repairs so I have to do this with your help if you can help
    I am grateful!

  4. Chris

    Chris Guest

    Jack, do you have a repair manual for the 466 scopes that I can
    obtain? If not, perhaps you have some testing procedures or
    instructions I can get?

    Thank You,
  5. Jim Yanik

    Jim Yanik Guest

    My first suggestion is to get a 466 SERVICE manual,with the parts
    lists,schematics,and VERY important;the CIRCUIT DESCRIPTIONS,which are very
    detailed,and tell how each section of your scope work.

    Try Ebay or,TEK no longer supports this model.

    In connecting to the AC mains,it's very likely that you burned up some
    ground runs on circuit boards.

    IIRC,TEK has some literature on why one should not make un-isolated
    measurements with grounded scopes.
  6. Chris

    Chris Guest

    Does anyone have an online version of the TEK 466 Service manual with
    the Circuit Descriptions that Jim recommends? I would bet these things
    are available in Adobe format.

    I would be grateful to anyone who has an online manual, if they would
    be kind enough to e-mail it to me.

    Thank You,
  7. James Sweet

    James Sweet Guest

    These scopes became "obsolete" long before Adobe Acrobat appeared, and
    before there was a practical way of moving computer files around if it had
    existed. They're still great scopes, but you won't find the documentation
    online, you'll have to buy the real manual or find someone who can photocopy
    the relevant section for you.
  8. TekMan

    TekMan Guest

    Hi Cris,

    as Jim pointed to: You need a schematic.

    for a guideline: Looks like the +15V pwr supply has dies during your
    "house AC test".
    Go to, do a search for tektronix and download the 475
    scope manual (jep, 475, not 466 - since there is no 466 in logsa).

    The pwr supply in the LV section is pretty much the same to the 466.

    And then download from from the
    Tektronix 466 operating manual -- this will help your friend teach how
    to use the scope.

    Both sites are free download, just follow the instructions (or google
    in the web).

    good luck for the repair.

  9. ------------------------------------

    [Flamers, note: This reply is "top-posted" so people using the Google
    Groups website don't have to click on "See the rest of this message".
    (Get over it.)]


    The power supply's test points' voltages (relative to chassis ground)
    should be labeled, right on the circuit board. If those voltages
    aren't all within a few percent of nominal, fix them before looking
    for anything else. You can also check the AC ripple on them. Most of
    them should probably have less than about 20 mv of AC.

    For Tektronix service manuals, there are many places to buy. At, they have truly-excellent-quality photocopies,
    with proper foldout schematics, nicely bound, etc., that are usually
    significantly cheaper than original manuals. I am not aware of *any*
    PDF version of the 466 service manual, although the sites mentioned by
    others do have the 466 *ops* manual. I have more sources for Tek
    manuals and info, listed at:

    I will also email you my list of the "best" sources for Tek manuals
    and parts.

    If you had another scope to use to troubleshoot your 466, it might be
    very helpful. The service manual has sample waveforms, etc, for you to
    check, in many places in your scope.

    You could also use another scope to build (in minutes) a "quick and
    dirty curve tracer", to test components (in-circuit, if you use a
    low-enough voltage; power OFF of course), such as the one described

    You could also use a second scope to test the ESR (Equivalent Series
    Resistance) of the electrolytic capacitors, which is a very good way
    to check for their common failure mode, using the technique outlined

    Another alternative: You should be able to find a 466 that's "almost
    working" at, probably for less than $100. Then you
    could compare measurments between that 466 and your 466. Maybe you
    could even fix that one instead. Either way, having two of them
    side-by-side can be a great aid in tracking down a problem.

    Good luck!


    Tom Gootee

  10. Scott

    Scott Guest

  11. David Gersic

    David Gersic Guest doesn't seem to be a valid hostname.
  12. Scott

    Scott Guest

  13. DaveC

    DaveC Guest

    They may be free from this site, but it seems restricted to Gov. employees.
    It asks for sign-in.
  14. DaveC

    DaveC Guest

  15. R3Jar

    R3Jar Guest

    The first thing you have to do is get a schematic. Once you find the schematic
    and are able to find the FAN you MAY find the entire problem. It is probably a
    power supply problem. But, you need to know what supplies are generated and
    where. Once you know that you are in business. Also, check very carefully for
    any more fuses. Sometimes they are very cleverly hidden.ince the fan does not
    run it may be just a matter of finding the powerr supply that suplies the fan.
    There may even be a sticker on the fan which will tell you what voltage it is.
    Then search out that power supply.
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