John wrote:

Thanks for the continuing input.
The LM79XX's will do you no good unless you have a source of negative
voltage to feed them. This generally will mean a dc to dc converter which
generally means switching regulators. Try putting your current
powersupply in a case and attach it directly to the MB's case and use
feedthrough capacitors in the common case bulkheads to feed the dc
voltage in. Put fedtrough caps and ferite beads on the dc in to the
powersuppply case. Cheep and will get you a good start to eliminating the
noise. John

About $1.00 a piece from a couple sources I checked. So about $7.00 for
the PS voltages plus the dc input. (although some are sold only in 10
lots) if you have multiple projects to use them up in you can order 100
quantity for about $.50 each.
John


Just checked Newark Catalog They have an interesting item:
A feed through teminal block with built-in filter capacitors
part # 95F895X
where x = number of terminals from 2 to 6.

Just something interesting to look into.
They have a lot of ideas for cap/ferite/filter ideas.
John