[R-390] R-390A balanced input question

[Roger Ruszkowski]

Jim,
 
You may want to check  the cables from the RF deck to the antenna relay.
for correct order and seating.
 
Common practice is to ground one pin of the balanced connector and feed the
other pin with the center conductor of a coax line with the coax shield also grounded to the receiver chassis.
 
When doing RF deck alignment this same set up is used.
You can not adjust the first cap in the RF deck transformer using this set up.
 
So a lot of fellows swap two of the three cables between the RF deck and the antenna relay.
This lets you drive the balanced input through the C connector with the other balanced input grounded
in the balanced input pin.

See Y2K 3.2.3 Field change 5 Shipboard use.

I see nothing in the Y2K to adjust the BAL caps in the RF deck.

You have to go back to TM 11 5820 327 35 The R390 manual for a procedure.
As the procedure is also not in the R390A TM 11 5820 358 35 .

Do you have CAL tones on every 100 KHz?

Roger AI4NI
 
 
-----Original Message-----
From: JAMES GREEN <jagreen3 at sbcglobal.net>
To: r-390 <r-390 at mailman.qth.net>
Sent: Sun, Sep 21, 2014 1:30 pm
Subject: [R-390] R-390A balanced input question


I have way too many projects to work on and just want to have a good receiver to 
listen to when I'm not in the shop. I have an EAC R-390A that I used to listen 
to quite regularly about a year ago. I put it aside for a few months and started 
listening more to 2 channel Hi-Fi. I had the yen to catch the BBC out of 
ascension Island again so I pulled it out and ran into a small problem.

Knew exactly where the radio was stored. I can't for the life of me find the "C" 
to so-239 adapter I used before to hook it to my antenna. I did find a balanced 
to SO-239 adapter, but I found I could not get a signal from the balanced input. 
Upon close inspection and some dis-assembly I found the plastic insert in the 
balanced connector was twisted. This twisted the relay contacts so there was no 
connection. I replaced the antenna relay with one from my parts radio & have 
verified it is now passing a signal. 

Here is the problem:

I still am unable to pick up anything through the balanced input. Upon looking 
in the R-390A Y2K manual schematics it looks like the unbalanced connector 
bypasses several tuned transformers that the unbalanced input does not bypass. I 
suspect these tuned transformers are in need of alignment. However, the 
alignment procedure in the Y2K manual instructs one to connect the sig gen to 
the unbalanced connector. & aligning from there.

Am I missing something? Is there a separate alignment procedure that I did not 
find that shows how to align from the balanced input?

Cash flow at the moment prevents buying another "C" to SO-239 adapter, & I have 
heard some extra sensitivity can be gained by using the balanced input.


Jim
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