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Help please with Tek 465 problem
(Yzordderex) wrote in
om:
I recently bought a Tek 465. It was working fine, but now scope
traces aren't sweeping across. Just a pair of dots where channels are
supposed to be. I'm not too familiar with this type scope and was
wondering if it's possible that I accidently moved a control and lost
the sweep. I've pretty much tried everything in the way of fiddling
with controls. But maybe secret button somewhere I don't know of.
A sweep mode,AUTO trigger,AC coupling.Press beam find to see if it's a
blanking problem.Does horizontal position control affect the display,or
just move the dots?
Ok, so assuming it's a problem inside scope, what am I looking at in
the way of circuits? Obviously there's a sweep oscillator generating
I would guess a sawtooth. Is there some kind of integrated circuit
with a Tek part number on it that's not going to be easy to get hold
of? Or am I likely to find run of the mill parts that I probably have
kicking around.
The scope uses a TEK-made sweep logic IC. 155-0049-0X. (-02 was the last
known version of this IC ) They do fail,but not often.(not a likely
failure,IOW) Could even be an unblanking problem.Check the CRT neck pins
for a sweep ramp.(accessible on the bottom board,red and green wires)
Vertical is brown and blue.
I guess what I'm asking for is for someone to take a peek at schematic
and give me thumbs up or down. I have another scope and my
troubleshooting skills are good, just don't have schematic in front of
me. If job is no-brainer I'll get hold of a schematic and go for it.
Otherwise have to ship it back to guy I bought from and pay him to fix
and ship back $$$.
Thanks guys.
Regards,
Bob
Well,first thing is to check the power supplies with a meter to see if they
are the correct voltages,then check ripple with a scope.Vary the line V to
check regulation.The electrolytics are known to dry out,even leak all over
the interface board.(bottom board)
The service manual has an EXCELLENT circuit description section that tells
you exactly how everything works in detail.It's a must-have.
--
Jim Yanik,NRA member
jyanik-at-kua.net
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