> I don't know if this is relevant, but recently I ran into this:
> I have been building a PIC programmer, and I used a 7812 with
> a voltage divisor  to boost the voltage slightly (to 14 V).
>        _____            The voltage measured with a voltmeter
> _______|    |________   looked fine, but when I looked at it
>        |    |   |       with the scope, it was 14VDC plus a 10MHz
>        --+---   <       oscillation with 1 Vpp amplitude. Kind of
>          |      >       shook my confidence in 78xx parts. I suggest
>          |      <       you look carefully for a parasitic oscillation
>          |      >       (of course hooking scope probes could influence
>          +------|       what you are looking for---welcome to the
>          |      >       wonderful world of analog).
>         ---     <
>     1uF ---     >       BTW, I ended up using LM317---works like a charm.
>          |      <
> ---------+------+-----
>
>                 greetings
>
>                         przemek klosowski (przemek@rrdstrad.nist.gov)

This would be caused because your ground was moving - right?

Probably some capacitance on the input line (on the 7812 side of your
voltage divider) would have solved the problem I think.

I took the liberty to put it in the picture.

Of course, I could be wrong.....

--

            -- Paul Greenwood --  (pablo@austin.ibm.com)

What the large print giveth, the small print taketh away.