Re: Tek 7904 Display Problem


patrick_vandenberghe@...
 

--- In TekScopes@y..., "Don Crano" <donc@s...> wrote:
Hi All

My old faithful 7904 has started to have a little problem with the
display.

It will run for hours or days with no problem. Then it will start
to drift
the display up and down, this is the trace/s and readouts as well.
Note this
is not on oscillation up and down. It will shift up for awhile,
then drop
down lower then it should be for awhile. I am talking about a 1/2
CM or so.
Everything is always on screen, it just gets annoying after awhile.

I found I can turn off the readouts and it will stop. Turn the
readouts back
on, and it will be fine again for a few hours or days.
Hello Don,

I had this problem. It turned out to be the channel switch hybrid
U625 (part nr. 1555-0060). This is located on a 'mezzanine' PCB
behind the two vertical plugins.
Some other sources mentioned the two 1W metal film resistors on the
vertical amplifier.

hope this helps

Patrick

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