19 Jul
2006
19 Jul
'06
8:26 p.m.
I wonder what those are? they don't sound rignt to
me, I would have
expected a 2-level singal only. I asusme all the power rails are nice and
stable (sorry, I've had that one all too often...)
Threw the scope on them, 5v looks O.K. (about 2.5x background noise (I'm using
unshielded alligator clip leads,
no probes yet). -5v +12v and -12v are all quite noisy. I don't know if this is a
recent development (I checked it out
after replacing some caps in the 5v section), or if the trick of using a DMM in AC mode to
check for noise doesn't
really work. I wonder if there's a common filter cap that's dried out somewhere,
or if ones on each channel have gone
(there are 4 boards, mains rectifier & smoother, chopper, -5 v and +-12v channels, and
5v at 100(something) A)
Maybe it would be easier to do another external filter cap on each channel. I'll look
at it a bit more and see what's up.