[R-390] BFO Question on Newly Acquired R-390A

[Craig Heaton]

Hello Chuck,

I don't think the following is in the Y2K, but..........found it on Chuck's
webpage years ago.

 Make sure the mechanical adjustments are up to snuff, they have to be
correct before the electrical is done. Proceed to the IF alignment in
section 6. Get it all done..........but before disconnecting all the test
stuff, put the jumper back on the diode load terminals. With the sig-gen at
455KC, turn on the BFO. Zero beat should be at "0". If not, undo either the
knob fastener or clamp, and set at "0" at zero beat.

Craig,

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of AE4CW
Sent: Wednesday, February 12, 2014 6:58 PM
To: R-390 at mailman.qth.net
Subject: [R-390] BFO Question on Newly Acquired R-390A

Hello Group,
 
This is my first post after acquiring a R-390A last weekend.  The radio
plays well on AM, and all the basic functions seem to be in the ball park
except one.  The BFO is offset by about 9 KC from the carrier.  At the "0"
position the BFO tone is very high pitched.  Turning the BFO to the far
right reduces the frequency but still is very high pitched.  I concluded
it's 9 KC from the carrier by peaking the carrier of a BC station in the 0.1
KC BW position, then listening for the BFO and zero beating in the 16 KC BW
position.  Zero beat is very nearly 9 KC above the BC carrier.
 
I don't see any way to adjust the BFO frequency other than maybe L509 inside
the Z502 BFO can which I presume is factory set and not accessible.  Before
I head down a rabbit trail, can someone please suggest the most likely
problem(s) and best approach to diagnose and fix?  Perhaps the whole 455 IF
strip is off frequency, but that seem unlikely to me.  No measurements taken
yet, but I do have the Y2K documentation.
 
Thanks in advance for your advice.
---
Chuck, AE4CW
 
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