[R-390] Mechanical Filter Failure?
Jon Schlegel
ews265 at rochester.rr.com
Wed Dec 19 19:37:30 EST 2007
Hi all,
Looks like it's case closed for the 2 kHz filter. Connected a 10k in
to out like Bob suggested and got signal. Removed the filter from
the chassis and ohmed the in/out coils and again got around 50 ohms
DC for both. Checked for shorts to case and found none. For that
matter, was able to resonate in and out coils to 455 kHz with 130 pF
or so of shunt C so it looks like the coils or ok. It's fate was
sealed though when I swept the filter and found virtually zippo
transmission. Thanks Bob C and John K, for the termination info on the filter.
Is the filter possibly fixable or should I be looking for a replacement?
Regards,
Jon
At 10:14 AM 12/18/2007 -0500, you wrote:
>Hi
>
>Before you go to crazy - sling a 10K ohm resistor between input and
>output directly on the filter. That should give you a quick
>verification that the signal path does not have any "gremlins" in it.
>
>Bob
>
>
>On Dec 17, 2007, at 11:09 PM, Jon Schlegel wrote:
>
>>Hi guys and gals,
>>
>>I'm working on bringing up an R-390A and have no response through
>>the 2 kHz mechanical filter. It's my understanding that the usual
>>failure mode for these is an open coil on the input or output yet I
>>measure 40 - 50 ohms DC on both input and output of the 2 kHz
>>filter. Checked the rest of the signal path around the filter
>>especially the rotary switch and all checks ok. Is there anything
>>else I should look at before thinking about finding a replacement?
>>
>>Regards,
>>Jon, WA3MVM
>>
>>
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