[R-390] R390: 60 Hz on Audio

[Jon Schlegel]

Thanks Roger,

I'm beginning to question the grounding arrangement that I used when 
I reinstalled the filters into the chassis after measuring them.  I 
will also look closely at the grounding accomplished by S502/503 rear.

ADDITIONAL INFO:  I removed V501 and injected 455 kHz to pin 5 
(plate) of the V501 socket and still see 60 Hz on recovered audio as 
previously described.  This does suggest the 60 Hz is getting in 
through the filter/switching/grounding arrangement as you 
suggest.  Exactly how the mechanical filters would be sensitive to 60 
Hz is still a mystery.

Jon


At 05:58 PM 6/9/2009 -0400, Flowertime01 at wmconnect.com wrote:
>Jon,
>
>It is clean and good on the 16KHz filter.
>V502 confirms the problem lies prior to the plate output of V502.
>
>Its back to the band switch and filter sections.
>
>It is not V501 as it does not appear in the 16KHz switch position.
>
>A wire for 2, 4, 8 is laying to close to a 60Hz source.
>
>S503 rear is not giving you the ground you expect on the 2, 4, 8 filter
>when you are selecting those filters. The switch section is not grounding the
>other filter sections as expected. The other filters are floating, picking up
>AC and passing it down the line.
>
>At 16KHz, either the switch section is working. Or the other 3 filters are
>not getting enough 60Hz coupled into them to present the problem.
>
>I think the 16KHz filter is picking up the 60 Hz and passing it down the
>wire when you are using 2,4,8. At 16 you change the switch setup and thus do
>not see any 60 Hz.
>
>Keep testing.
>
>Roger AI4NI
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