Re: Problem with Tektronix 475 "ADD" function

david@xxxxxxxxxxxxxx wrote in
news:1132017601.123108.96430@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

> Jim and JURB,
>
> Ok, I've checked the value of the offset that appears when using the
> "ADD" function and it is a constant one division (5 subdivisions)
> regardless of the vertical scale deflection setting. (Of course, both
> channels are always set to the same vertical deflection). So does this
> suggest that the problem is in the channel preamps or a following
> stage?

I'd say that the problem would be in the preamps.
I can't recall if there's a spec on offset for the "add" function.
The "invert" function for Ch2 is done by one of those spider IC's I
mentioned,and IIRC,there's a DC balance adj.for the inverted Ch2.(I could
be wrong;no schematics for reference)

It might be that the Ch2.invert-add function is not spec'd for DC offset.
You would have to center the trace with no signal input,then make your
measurements.

>
> Also, I poked around the vertical switching circuit on the input side
> to U370 (monolithic switch) and found all DC voltages to be consistent
> with the schematic, thus suggesting that there's nothing wrong with it.
>
> Suggestions?
>
> Thanks. This is very helpful.
>
> Best,
>
> -Dave
>
>



--
Jim Yanik
jyanik
at
kua.net
.

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