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Thomas P. Gootee
 
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Default Tektronix 466 Scope Problem

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[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.)]

Chris,

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
http://www.w7fg.com, 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:

http://www.fullnet.com/u/tomg/links.htm

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
at:

http://www.repairfaq.org/REPAIR/F_semitest.html#stqdc

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
at:

http://www.fullnet.com/u/tomg/esrscope.htm

Another alternative: You should be able to find a 466 that's "almost
working" at http://www.ebay.com, 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!

Regards,

Tom Gootee

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chris1@oupower_dot_com (Chris) wrote in message om...
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 "****ed off"
expression.

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 ****ed. I take pride in all of my equipment ...no 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,
-Chris