Re: 7904 readout 'jitter'


Craig Sawyers <c.sawyers@...>
 

I have a 7904 where the on-screen readout vertical position is
slightly depending on the vertical trace position.

On a steady beam this is not a problem but if you put the horizotal
time base in alt, the readout becomes bouncy. I think the problem is
in the unbalance of the vertical amp, but would like to hear some
other people about this 'problem'
Well, Fred - my 7904 is the same. The same thing happens slightly with my
7704A, and not at all with the 7834 and 7104. I've done a complete recal on
the 7904, and all offsets in y and t are absolutely on the button.

I suspect that it may have to do with the horizontal amplifier - there were
(at least) three different circuits that were used (B21000 and up, B080000 -
B209999, B010100 - B079999). The very earliest range of S/No.s had a
thermal balance control that was set to reduce readout jitter to less than
0.1 div, but this control does not exist on later units.

FWIW mine is in the middle range, with S/No B113428.

Any other information greatfully received....

Craig

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