[sdiy] yard sale find

[harry]

Yes (and of course Jim knows this but...)

Adding a probe and having the circuit WORK usually means the
circuit is lacking some resistance (like 10 megohms) or some
capacitance (like 10pF) to ground.

Good hint for troubleshooting.... maybe something likes the load (like
a non-inverting opamp input with no way to get its input bias current ???)

If a probe fixes it... I try a 10 megohm resistor or a 10pF cap (or both) to
ground...

H^) harry

patchell wrote:

> John L Marshall wrote:
>
> > Out of context it reads wrong. I was describing the load. Too much load.
> >
> > All measuring equipment influence the device under test. The question is how
> > much influence? The frustration is when the influence causes unexpected
> > results.
>
>     Yes, and the unexpected results I usually get is that loading the circuit
> with the probe make the dang thing work...how are you supposed to fix the
> problem if the thing you are looking at the problem with fixes it (if I
> remember, this was some sort of quantum mechanics phonom... :-)  ).
>
> >
> >
> > Take care,
> > John
> > ---------------------------------------------------------------------------
> > Pacific Northwest DIY Synthesizer meeting, July 20, 2002
> > See: www.sound-photo.com
> > ---------------------------------------------------------------------------
> >
> > ----- Original Message -----
> > From: <media.nai at rcn.com>
> > To: "harry" <harrybissell at prodigy.net>
> > Cc: <synth-diy at dropmix.xs4all.nl>
> > Sent: Tuesday, July 30, 2002 8:57 AM
> > Subject: Re: [sdiy] yard sale find
> >
> > >
> > > >Even the 10 megohm resistance of the 10X probe is sometimes too much.
> > (you
> > > >>can't
> > > >
> > > >-for instance... look at the voltage on a sample/hold capacitor... just
> > > >>will not work)
> > >
> > > Don't you mean the "10 megohm resistance of the 10X probe is sometimes not
> > > enough"??
> > >
> > >
>
> --
>  -Jim
> ------------------------------------------------
> * Visit:http://www.silcom.com/~patchell/
> *-----------------------------------------------
> *I'm sure glad Merry Christmas comes just once a year
> * -Yogi Yorgensen
> ------------------------------------------------

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