H744 regulator whistle

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Sat Jan 12 18:57:51 2002

I have two H744 regulators in my PDP-11/40, along with an H7441, H745, and
H754. I also have two spare H744s and one each H745 and H754. All the
H744s emit a fairly loud whistle, and it's driving me nuts. I've seen a
note somewhere that a loud whistle is caused by the coil de-laminating, but
I don't think that's the case. I tried swapping the two original H744s for
spares, no difference. I also tried swapping the coil from the spare H745,
which runs almost silently, and that made no difference either. I don't
think I can just remove (short out) the coil either, as this is a switching
regulator and the coil is needed to make it work properly.

Any suggestions?

-- 
Pete						Peter Turnbull
						Network Manager
						University of York
Received on Sat Jan 12 2002 - 18:57:51 GMT

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