[R-390] Physical Location of C568 - C571

[Jon Schlegel]

Hi Dave,

Thanks for the info on Figure 15.  I saw that also but as you know it 
doesn't show exact locations.  The schematics in the TM 11-856A 
download also refer to a table and figure (note 2, sheet 3) which 
appear to be part of some other manual.  Dennis, WA6ACC sent me a pdf 
of one of Dallas Lankford's articles whose photos show which trimmer 
is wired to which filter.  For reference, this article shows how 
Dallas replaced two of the mech filters with newer generation filters 
explicitly for upper and lower sideband.

Regards

Jon

At 10:02 AM 4/24/2009 -0700, David Wise wrote:
>There's no drawing or photo that I know of, but
>the correct connection can be deduced from some
>manuals.
>
>The trimmers should be paralleled by fixed mica caps.
>All of the fixed caps are 82pF except C507 and C516
>on the 16kHz filter, which are 51pF.  So find the 51's;
>the associated trimmer goes to the 16kHz filter.
>
>(Note: Some 8kHz and 16kHz filters are special and
>do not use the fixed output caps.  In this case, the
>caps should be present but not connected.)
>
>This information is not in the original TM 11-856A.
>In TM 11-5820-358-35, it's Figure 15 (Modified
>mechanical if. filters), on page 26.  (Someone added
>this figure - without the page number - to my scan
>of TM 11-856A.  I don't remember where I got this
>scan.  It's dated October 4, 2001, and it's
>44,335,104 bytes.)  In Y2K-R2 and Y2K-R3, it's
>Figure 3-6, on page 3-16.
>
>Dave Wise
>
>-----Original Message-----
>From: r-390-bounces at mailman.qth.net 
>[mailto:r-390-bounces at mailman.qth.net] On Behalf Of Jon Schlegel
>Sent: Friday, April 24, 2009 8:12 AM
>To: r-390 at mailman.qth.net
>Subject: [R-390] Physical Location of C568 - C571
>
>Hi all,
>
>I'm assembling the topside mechanical filter compartment of a 390A IF
>module.  The documentation I have (TN11-856A) is not clear as the
>exact physical location of the trimmer caps, C568, C569, C570 and
>C571 that tune the output transducers of the filters.  The reference
>designators stenciled on the top of the filter shield box locate
>these trimmers at the top corners of the shield box when in fact the
>trimmers are mounted to a "plus" shaped bracket placing the trimmers
>"in between" the filters.  It would be just as easy to wire a given
>trimmer to either of two filters.
>
>What is the correct relationship of these trimmers and their filters?
>
>
>Regards,
>Jon Schlegel WA3MVM
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