[R-390] 1.0 and 0.1 filter settings

[Barry]

Dan,

Thanks for the reply.  I see what you're talking about now.  I didn't
realize the cap's job is to "bypass" the crystal, but okay on that.

The problem seems to have fixed itself somewhat.  I'm in the process of
recapping the IF deck.  I'm replacing a few caps at a time and testing
between each "session" to make sure I haven't toasted anything.  If it stops
working, I'll be able to narrow down where I may have botched something.  I
replaced the two cathode bypass caps last night and DeOxited the bandwidth
switch contacts.  The last test seemed to be a lot better than the first
one.  The signal doesn't drop nearly as much as before.

I washed the deck thoroughly Saturday afternoon and thought I had it dried
out pretty good, but perhaps there was still a bit of moisture hiding in
critical places and that may have dried out better overnight.  Perhaps the
cathode bypass caps in the first IF amp were leaky.  Not sure what improved
it, but it appears to be working now.

Six paper caps down in the IF deck and nine more to go.  I'm sure glad this
is my hobby!  Some of these are a real pain to replace!

Thanks,

Barry - N4BUQ

----- Original Message ----- 
From: "Dan Merz" <djmerz at 3-cities.com>
To: "'Barry'" <N4BUQ at aol.com>; <r-390 at mailman.qth.net>
Sent: Sunday, April 10, 2005 2:57 PM
Subject: RE: [R-390] 1.0 and 0.1 filter settings


> Barry,  the crystal may appear to always be in the circuit but it is
> bypassed by C501 when the switch is in the 2,4,8,16 positions.  The
crystal
> filter is effective only in the 1 and .1 positions.  Apparently something
is
> not adjusted correctly in the crystal filter or the crystal is defective,
> which is causing the filter to reduce the gain considerably.  I don't
recall
> messing with the crystal filter neutralizing in my 390a which is covered
in
> the Y2K manual; others may have words of wisdom about problems that arise
in
> the crystal filter circuit,  Dan.
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of Barry
> Sent: Sunday, April 10, 2005 12:01 PM
> To: r-390 at mailman.qth.net
> Subject: [R-390] 1.0 and 0.1 filter settings
>
> Can someone give me the "Reader's Digest" version of how these two
settings
> work in an R390A?  I'm working on restoring the modules for my newest
> project.  After replacing C553 (just to be safe), I plugged it in place of
> the IF deck in my working R390A.
>
> It seems all four filters are working; however, when I switch to 1.0 or
0.1,
> the signal disappears almost completely, no matter how closely I tune to
the
> frequency.  I can see that the crystal and its parallel adjustable
capacitor
> are always in the circuit, but going to 1.0 switches out the extra cap and
> switching to the 0.1 position adds some extra circuitry into the mix.
>
> I don't quite understand how these other two settings do their job.  If
> someone could elaborate, I'd appreciate it.
>
> Thanks,
>
> Barry - N4BUQ
>
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