[R-390] Broadcast Band On Other Bands

[Bill Smith]

For what it is worth, I have the same problem in a Hallicrafters SX-62.  It
plays beautifully, then gain suddenly cuts down by quite a bit.  If I switch
mode to cw and back to am, I can restore normal operation.  I have recapped
the receiver and checked all the resistors.  I suspect one (or more) mica
caps inside one (or more) of the IF cans is opening up.

Couple of other notes.   The R390 (non-a) here is still overloading on the
AM broadcast band.  I have recently rocked the bandwidth switch only to
discover that the center of the bandpass changes when I hit just the right
spot.  Perhaps the problem is a combination of a recent alignment, and the
condition of the bandwidth switch.   Further, apparently due to my
alignment, there are now two peaks in the 16 kHz position.  The switch was
cleaned, but apparently not well enough.  I have samples of a conductive
material, will have to try that the next time I can dig into the receiver.
Perhaps this is the solution to the overload problem discussed previously
(one can always hope).

In the RF section, I now notice some bands will increase in signal strength
slightly when the MHz Change switch is rotated slightly.  This is a
departure from when I first obtained the receiver.  Do R-390's need periodic
realignment in the RF section?  The set was pretty gummed up, perhaps it is
only now loosening up a little.

73 de Bill, AB6MT
billsmith@ispwest.com

----- Original Message -----
From: "blw" <ba.williams@charter.net>
To: <R-390@mailman.qth.net>
Sent: Tuesday, April 23, 2002 8:45 AM
Subject: Re: [R-390] Broadcast Band On Other Bands


> Yes, mine is a 56 Motorola and you described the effect better. It is a
> sudden gain without noise or harmonics. I have not had the IF or RF deck
out
> to check manufacturers, but I am betting they are Motorola modules based
on
> consistent metal work, lettering, and MFP type.  It is pretty easy to look
> at everything and come to the conclusion everything was manufactured at
the
> same plant. The PS and audio deck are Motorola. I am using an EAC audio
deck
> at the moment until I can recap and replace resistors in the original. So,
> the audio deck is eliminated as cause of this phenomena.
>
>
> Barry
>
>
> > Mine does the same thing.  It's almost like it gets a sudden 10dB gain.
Is
> > yours a '56 Motorola?  I wonder if it's manufacturer/contract specific.
> >
> > Barry(III) - N4BUQ
> >
> >
> > Mike,
> >
> > This makes me think of several things. First, I sometimes get a sudden
pop
> > of louder audio especially if I've had the radio parked on a frequency
for a
> > long time. Something seems to open up somewhere for full audio. It has
been
> > going on for a few years now. Turning up the RF Gain usually gives me
full
> > audio again, or turning the MC Change knob up or down a band will do it.
I'm
> > pretty sure that the racks are moving loose enough to not bind like they
do
> > on my other one. Sometimes I get the impression that crud on the Local
Gain
> > and RF Gain pots is causing the problem.
> >
> > Maybe some of these stations are harmonics?
> >
> >
> >
> > Barry
>
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