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My R7603 has developed a problem where the readouts jump around a lot based on the input signal frequency and amplitude, signal trace is fine. With no input, readouts are steady. This readout problem occurs with several different vertical and horizontal plugins, problem appears to be in the 7603 frame.

Power supplies measure well and look good on scope, dont think they are involved. I have been unable to determine if the readout board or the vertical or horizontal amp board is involved as I do not have spares.

Has anyone seen this problem and resolved it?

Larry

I have had similar on a few of my mainframes. More pronounced in some with
7A12's and the traces DC offset/positioned high or low on the CRT , etc.. (I
have not 100% decided it's the same issue).

In any event, I got marked improvement in the most gross case by fixing the
loose card slot side. Not sure what they're called but the little plastic
pieces that go on both sides of the card slot. In the other case I had not
tightened the readout card screws well so a grounding issue I can but
assume.

That said they still all still do it with the 7A12's (I actually have 4 that
do the same thing). I therefore assume that there is some feedback pathway
that exists in general between verticals and the Mainframe but TEK fixed it
in other/later plug-ins. I can but assume that there may be a fix on the
mainframe side as well.

As a suggestion, perhaps look at your serial number and later ones with
specific emphasis on any cap size changes on the readout card, etc.
Decoupling caps in particular?

In any event, I will be highly interested in what the peoples with the true
expertise have to say about this one. As I truly am only sharing experience
vs. any real insight I know.

I hope this finds you well
Rob

In the mainframe cal procedure, specifically for the vertical output
amplifier, look for an adjustment called thermal compensation.
It may help. It would be a good idea to check the HF response if
this is tweaked..
-ls-



"photo692002" <photo692002@...> wrote:

Jumping readouts resolved.

After tracking signals from readout board to V and H amp boards everything
looked OK, however when looking for XY signal on vert interface it was missing.

Turns out interconnect cable between H amp and main interface board had came
loose from main interface connection. After reinstalling everything is fine with
readouts.

Thanks to those who responded.

Larry