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Chris
 
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Default Tektronix 466 Scope Problem

On Mon, 10 Nov 2003 02:30:08 GMT, "James Sweet"
wrote:

"Chris" chris1@oupower_dot_com 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


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.



James,

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!

-Chris