12 Jan
2002
12 Jan
'02
11:54 a.m.
Sometimes it helps to fasten coils a bit with siliconekit
or araldite, or if a bit of heat is not a problem thermal-glue
Silicone kit has the added benefit of dampening high freq.
vibrations cause it has a somewhat rubbery constitution....
Do not totally immerse the coil in glue cause you might run
into thermal problems, just enough to fixate it a bit (better).
It worked for me in TV-sets with a similar problem
Sipke de Wal
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----- Original Message -----
From: Pete Turnbull <pete(a)dunnington.u-net.com>
To: Discussion re-collecting of classic computers <classiccmp(a)classiccmp.org>
Sent: Sunday, January 13, 2002 1:57 AM
Subject: H744 regulator whistle
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