Re: 454 with no vert. deflection


mtmpsmp@...
 

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:
mtmpsmp@y... wrote:

I have a 454 that has no vertical deflection on ch1 or ch2, using
another scope I am able to trace signal from the preamps to the
deflection plates. The sweep appears to be in good shape and the
trace is centered on crt. ( position controls have no effect on
trace) What I don't understand is that I have a voltage imbalance
on
vertical plates and the trace is still centered!
Boy! I don't understand that either. I have to wonder if the
voltage
unbalance is actually getting to the deflection plates inside the
CRT.
Perhaps there is a broken connection INSIDE the CRT. If the
unbalance is
actually on the CRT plates, I don't see how the trace can be
centered
vertically . . .

Stan
w7ni@e...
.....................................................................
......................................................................
Stan,
Upon further investigation I have found that when the scope is
turned on the collector voltage is the same (74.6 volts) on each
output device. The voltage will stay in that condition ( flat
centered trace) until I start making voltage measurements with my
voltmeter ( high impedance digital) then the top connecter drops to
56.8 -62.0 volts and the bottom to 32.5 -29.8 volts, the voltage of
course being determined by position control. The trace is at this
point off screen in all modes ( chop, add ect) I can seem only to
bring this condition on by taking voltage measurement on either vert
plate.
Do you think maybe a bad output transistor? thanks for your help.
Mike


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