[R-390] Dead except 0 to 1 Mhz R390 non-a
Roger Ruszkowski
flowertime01 at wmconnect.com
Tue Mar 24 02:00:08 EDT 2015
Dan,
Letting these receivers just set is not a good idea.
They like to get the mechanical switches moved around to help
keep the switch wiper contacts clean.
Larry pointed you to the antenna relay contacts.
Try an antenna into the unbalanced input and see what you get.
Just .5 to 1 meg working is not a logical problem.
So antenna relay a good place to start.
sensitivity is so low across all bands that only the three strong AM stations get through.
Here you are looking for crud on a tube pin.
Pull all the tubes one by one. look for an oxidized pin. reinsert each tube a time or two
to cause the tube pins and socket plugs to get scraped clean.
De Oxit helps a lot.
Some radio Shack electronic parts cleaner is a second choice.
Give the wire harness to deck connectors the same treatment.
Triage starts with 150 uv of 455 KHz into the IF deck with - 7 volts on the diode load
and with 30% modulation from the signal generator almost a 1/2 watt on the local output
on the back panel.
You can use the R390A trouble shooting guide found several places on the web.
The test points and tube numbers will change but the procedures follow the same sequence and test values
Between CW and modulated AM you will want about 26 - 29 DB difference in level.
If you can not get this out of the IF deck and Audio deck you will never get the
receiver up to 10: 1 over all or close to the 20:1 it will do.
Once you get the IF and Audio working you can go for MGC on the RF deck
and then AGC on the receiver in general.
Do not give up there is nothing in the receiver that can not be fixed.
Some of your comments indicate the RF band switch may have some crud on it.
Pulling the RF deck in your R390 is a bit more complex than doing it for an R390A
but you may have to go there.
Just start with the other stuff first and enough knob twisting may work the
band switch contacts clean enough to be OK.
Roger Ruszkowski AI4NI
-----Original Message-----
From: Larry H <dinlarh at att.net>
To: Dan Merz <mdmerz at frontier.com>; R-390 List <r-390 at mailman.qth.net>
Sent: Tue, Mar 24, 2015 12:29 am
Subject: Re: [R-390] Dead except 0 to 1 Mhz R390 non-a
Hi Dan, Could be the antenna connection or relay, rf amp, or if amp. Good
luck.
Regards, Larry
From: Dan Merz <mdmerz at frontier.com>
To: R-390 List
<r-390 at mailman.qth.net>
Sent: Monday, March 23, 2015 9:11 PM
Subject: [R-390]
Dead except 0 to 1 Mhz R390 non-a
Hi, I haven't used my R390 for about 2
years and decided I needed to check
it out compared to other lesser radios I've
been using recently. It's been
sitting there in the best spot in my radio area
and other than hooking up
the speaker it should have been ok. It was still set
on 80 meters where I
used it last but when I turned it on it was more or less
dead except I could
tell the audio was working but no indication of signals or
ability to peak
noise. I finally went down to the broadcast band and was able
to tune in
the three strongest local am stations between 600 and 1000 khz.
The
Megacycle change knob seemed to be the key to getting it to work and it
was
very sensitive to position and would become alive by moving the Mhz
change
knob slightly. And it sounded ok but I think the signal level is
somewhat
low on the meter compared to what I remember for the one station that
I
listen to the most at 960 khz. And it suddenly goes dead occasionally
when
I'm not touching the set but is revived by more or less moving the
megacycle
change knob slightly. I tried the higher bands but could get no
response on any
band despite a lot of motion on the Mhz change knob. Is
there one particular
switch that is the likely culprit? This radio has been
pretty reliable in the
past after I worked it over quite a bit after getting
it 10 years ago but I
don't recall having any problems with switches back
then. I have the manuals
but thought there might be something obvious that
others have encountered.
Thanks, Dan
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