[R-390] Capehart made R-390A Serial #312

[Larry Haney]

Hi Karsten,  Those 2 resistors set the bandwidth of the .1 and 1 kh
bandwidth switch positions.  If the crystal you receive is close to the
original specs, the bandwidths should be close as measured by the procedure
in the tech refs.  If they're close (within 10%) , I would not bother
trying to improve on them.

Here's a little more detail on the operation of the '0 adjust'.  It's
Range is about 15 kh end to end, so +/- 7.5 kh from the center.  The
bandwidth at the output of the RF deck is wider than that, so as long as
you can use the '0 adjust' to 0 the readout, you should not see any
degradation of operation.

Regards, Larry

On Sat, Apr 12, 2025 at 4:34 AM Karsten Simon via R-390 <
r-390 at mailman.qth.net> wrote:

> I am done with checking and realigning (wherever possible) the various
> crystal oscillators. One issue still open:
>
> The Y501 crystal (455 KHz crystal filter) is missing. Will have to get a
> new
> one made by Quarztechnik Daun (Germany).
>
> Question:
>
> .         Will this replacement have influence on R502 and R503?  (-> Note
> 1
> on Circuit diagram = Fig. 5-13 Sheet 3 of 4 in NAVSHIPS manual
> 0967-063-2010). If so, how do I determine the correct new values?
>
> -- Karsten --
>
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