Jeff W wrote in
:

AFAIK, there are no easy workarounds. As you probably are aware, Tek
came out with a retrofit kit that replaced the nasty triac prereg with
a TL594 based MOSFET prereg like in the later 2215A series. Actually,
the TL594 prereg is not that complex; I thought about building up a
small kit myself; but I would have to come up with one part that would
not be easy; the buck transformer. I have a couple of dead 2235's
around here; maybe someday I'll unwind one of those to see about
replicating them.

Jeff

On Mon, 16 Feb 2004 20:58:33 -0700, Don Lancaster
wrote:


Every once in a while one of these comes up with a back panel singing
inductor that up-the-wall whines.

I tried everything reasonable involving damping the tuning fork like
shield, rubber mounts, etc.
Still could not get the noise acceptably low.

This is apparently a chronic problem that infects a significant number
of 2215's and probably 2213's as well.

Any cures or workarounds out there?



Or you could create a ordinary (60Hz)transformer based 43 volt DC supply to
replace the pre-reg.It would have to supply at least 1 amp at 43V,and would
only work for whatever primary voltage you selected for the XFMR,not the
90-250 VAC range of the Opt.48 pre-reg.

--
Jim Yanik
jyanik-at-kua.net