PDP 11/45 partial success.

Eric Smith eric at brouhaha.com
Fri Mar 18 15:45:04 CST 2005

Jim wrote:
> after a few days frustration, I have got a little further with my 11/45.
> The power supplies checked out OK with respect to ripple and output, but a
> couple have them have the odd VERY fast spike on them - is this normal?
> (I'm using a 100MHz 'scope - I suspect they may not be visible on a

They are switching power supplies, so there will be some high frequency
noise.  I'm not sure what the typical switching frequency is, though I'd
guess that it would be in the 100-200 KHz range; maybe Tony Duell knows.
Anyhow, one would expect some very high frequency spikes occurring at
the interval of the switching frequency.  But the spikes shouldn't have
very high amplitude; if they do, it's possible that you have some bad
filter capacitors.

I'm out of my element on analog stuff, so hopefully someone else can
help you more.


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