[R-390] R-390a modified IF sub-chassis

[Gary I. Biasini]

Bill,

Thank you for taking the time to respond and to provide the copy of the
article.  It was very helpful and in fact, you appear to be correct.  I had
seen reference to Eugene Hubbel's modification of Capt. Lee's approach but
was never able to find it.

As I have mentioned to a couple of other people on this list who kindly
provided their help, I sincerely apologize for the time it has taken to
respond.  I am often not in the same city as my radios and, when with them,
often have other time constraints that prevent me from spending the time
that I wish I could to get to them.

Back to the modification.  I traced the schematics on the article that you
provided.  Except for a couple of minor component changes (the .02 capacitor
was a .068 in mine, the electrolytic was 1,000 uF at 25v (rather than 50v)
and the 51K 1W resistor was a 33K 1 W resistor (probably matched to the
relay used))), most appears identical to the article, EXCEPT, there were no
modifications on the panel on R120, i.e. the addition of 1.2K and 100K
resistor to and between R120 , the switch on R120 and the function switch
S102 (as detailed in paragraphs 17 and 18 of the modification.  The purpose
of the last part of the mod is to provide a positive cutoff of audio feeding
through noise limiter tube when the limiter control, R120, is advanced.

The major problem that I find now is that, when I turn on the BFO, the radio
goes completely silent, almost as if the signal path was completely
interrupted.  If anyone has any suggestions in this regard, I would be most
grateful.

So, what else have I done when I found time on my Teledyne S/N 2697?  Even
though I was away from the physical location of the radio, I can read what's
on the web anywhere so I spent time researching how to further bring the
radio back into peak condition.

I have now set the end points of the Progressitron PTO (they were about 6Khz
off) using a BC-221 frequency generator to check the end points since I
could not use the BFO and the 100 KHz calibrator.  I have adjusted the dial
lock for center and then the veeder root for center (I now have 34 KHz
overrun on each end) and then adjusted the cams to line up with their
respective marks on the chassis.  Finally, I adjusted the PTO to read
exactly at the indicated frequency on the veeder root and, at least
mechanically, the receiver now appears to be aligned.

Once I tackle the issue of no BFO, I will try and tackle the alignment of
the RF and IF modules and see what I can do about getting this radio back to
spec.

Again, thanks to all for your help and, hopefully as I progress and learn
more, I can be of help to others.

Best regards,
Gary

-----Original Message-----
From: Bill Cotter [mailto:n4lg at qx.net] 
Sent: Thursday, September 28, 2017 12:17 PM
To: 'Roy Morgan' <k1lky68 at gmail.com>; r-390 at mailman.qth.net; Gary I. Biasini
<gary.biasini at shaw.ca>
Subject: R-390a modified IF sub-chassis

Gary,

The schematic you sent looks very much like the W7DI product detector
modification that was published in Ham Radio Magazine July of 1974 (see
attached).

I have used this particular modification in two of my R-390A's. It works
great, and does not require a panel mod. And, the IF deck can be
interchanged into any R390A.

73 Bill N4LG

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