Re: Quickie 465 repair?


Bob Koller <testtech@...>
 

It is also possible that one of the little plastic plug-in attenuators is intermittent. I have repaired many of these. Inside, the ceramic substrate is soldered to pins, the solder breaks loose. You need to be very careful re-soldering, using silver bearing solder and a low temp iron, or you will leach the pad off the substrate. Or, find a replacement. It will require readjustment.

It may also be, as the other responder said, the atten contacts need to be cleaned. Usually, though, you can wiggle the knob and the observe the amplitude change. Note that there are contacts on both sides of the preamp board...


From: Ron York
To: TekScopes@...
Sent: Saturday, April 28, 2012 8:26 AM
Subject: [TekScopes] Quickie 465 repair?

 
I have been getting great use out of my "new" 465. Love it!

There is only one major issue that is getting in the way of my use of
the scope, and I am wondering if it might be a quick fix, like contact
cleaning, or if it will be more involved. I am planning on going in
and doing a thorough R&R (after more time pouring over the archives
and manual, etc), but I am busy on a project at the moment.

The channel 2 V/div knob works fine in the ranges above .2v (.5-50v).
But when I switch it down to .2, the waveform excessively increases in
size and goes off the screen. The waveform will go from 2 divisions
in height to maybe 10 or 15.

I can use the position adjustment to move it up and down the display.
Also, if the test waveform is a a square wave from the CAL source, the
initial peak or bottom corner of the wave becomes rounded. That
rounding of the corner does not happen in the higher voltage settings.
Exercising the selector does not seem to influence the problem.

This problem happens most of the time, though it did stop once after I
had the scope powered on for a while. Though hours of runtime does
not usually clear the problem. The scope chassis does get warm with
use, but I'm not certain how warm it should get. I seem to have
reasonable airflow through the fan at the back.

Any thoughts?

Thank you,

Ron


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