Re: Tektronix 453 trace way off-screen horizontally

Wolfgang Meier <womei@xxxxxxxxxxxxxx> wrote in message
news:1158072757.507240.320610@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi all,

I recently got hold of an old Tektronix 453 oscilloscope. It seems to
work just fine, but the trace seems to be way off-screen horizontally:

When I press the "beam finder" button, which is supposed to compress
the display to fit all of a trace, I can see the trace running as a dot
that moves about 1/16th of a div at a position of approx 75% of the
display's width. I can adjust the horizontal position of that dot by
about 1/2 div. When I release the "beam finder" button, I get a
horizontal streak to the right and the trace is gone again.

After opening the cover and measuring the horizontal deflection plates'
voltage (to ground), one plate constantly read approx. 110V, the other
0V, which seems to be off-scale - I expected something like a sawtooth
of approx. 75V on both. When I shorten the plates, the dot is
dead-center.

Could it be that something is wrong with the horizontal amplifier
circuit?

I hope this is a common fault of this series and you can give me blind
advice on where and how to check for errors - I wouldn't know where to
start...


Thanks in advance,

Wolf


Swap the two final driver trannies or replace them both with something
voltage/current-wise suitable and see what happens, go for proper
replacement later if nominally corrected.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



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