Thank you. Since its a different choke it doesn't explain why the
original was humming. Doesn't matter if the problem is solved but would
be interesting to know. Its possible there is a leak between the winding
and core or frame in the original. A sensitive ohm meter would probably
tell. I had thought of suggesting putting the old choke on an insulator
(just a sheet of paper) temporarily to see if the hum stopped. Not worth
taking the new choke out to try.
The SX-28 is an interesting receiver, an attempt by Hallicrafters
at advanced engineering that didn't quite come off. The Lamb noise
blanker was a very good idea but was not well implemented. Eventually,
Drake and others, did a better job with it. This type of blanker works
well on pulse type noise, like ignition noise, but hardly at all on the
more common (now) power line noise. Hallicrafters eventually published a
modification (on BAMA) to disable it and replace it with a conventional
series limiter. I hope not many SX-28s were mutilated this way.
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On 2/19/2025 11:57 AM, thoyer via groups.io wrote:
Yes, I replaced the original CH2 with another 4hy one I had from an
R390A AF module.
On Wednesday, February 19, 2025 at 02:43:41 PM EST, Richard Knoppow via
groups.io <1oldlens1@...> wrote:
Please clarify, do you mean you replaced the original choke and the
problem went away? If so it could confirm my idea of filament current
somehow coupling through the chassis.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
