This belongs in the For What Its Worth file:
I cannot help but note that the venerable Kenwood TS-930S and TS-940S
rigs had their big hunk of a power transformer mounted right next to the
PLL section - and no hum problems were apparent, and it was NOT a
toroidal type transformer, just a standard E+I section type, with no
outer cover - you could see the laminations and windings.
Yes, the PLL assemblies were inside shielded compartments, but there did
not appear to be anything special about them - specifically, they were
not "Mu Metal", although they were steel. However, the radio would
operate just fine when the shield covers were open - as during testing
and alignment, so the shielding or lack thereof (in the Kenwoods) was
not germane to that sort of problem. What was different about their
design that made it "hum proof" - at least from fields induced by the
mains transformer?
So, maybe the problem could be worth another look, as in maybe there is
another way to solve it? Could something be done to the K2 itself to
make it immune to this problem?
This needs someone who is a better engineer than me to come up with an
answer- I am just a lowly self-taught fumbler.
73, - Jim, KL7CC
Michael Harris wrote:
G'day,
By coincidence I opened up our stereo amp to have a go at lubricating a
noisy volume pot. I noticed that the torroidal mains transformer was of
shielded construction.
Maybe this is the answer to the PSU hum coupling problem. A 20A psu in a
double height EC, speaker etc as has already been suggested.
Regards,
Mike VP8NO
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