[R-390] 51J-4 in Denmark

[Clemens S.Ostergaard]

Hi everyone,


Having been away from the list for a while, I can report a lucky break. I
have long wanted to supplement my R390A=92s and SP-600 with a Collins
51J-4. I finally located one, perhaps ex-NATO HQ in Jutland. It turned
out to be almost unused, the rotary dial not the usual butter-yellow from
heat and smoking, in its original black wrinkle case, with original
manual and RCA valves (no tools though). Not a scratch or wear mark, so
perhaps it has been a spare, or somehow supernumerary. The VFO did not
need end-point adjustment and it does not vary more than 1-1,5 Kcs over
the whole range.


The s/n is 3026 (at least on the label, on the back the receiver has the
number 109 stamped not engraved, but I think this is unlikely to be the
s/n since the manual is dated 1960 and 109 would be from 1957. Any
comments? Any other places to look for dates, I don=92t see any obvious
candidates?) Front panel is black wrinkle, - personally I like the
=92non-black=92 versions which contrast with the many black knobs. Perhaps
only the R-388A came like that? Is that the colour called St.James gray
wrinkle?


It is unmodified, apart from the usual Danish military practice of
replacing the 51J-4 meter with a small loudspeaker. It has been possible
(thanks to my friend Ib M=FCller) to find a suitable replacement meter ,
and copy the correct meter scale. Replacement of an electrolytic and the
missing 100 kcs. crystal, and a thorough overhaul so it looks and feels
like a new set. 


The little I have tested it (with a T2FD and a trap dipole) seems very
promising. It is indeed useful to have the mechanical filter at 6
Kcs.(and the other two) and the crystal filter gives an early version of
a notch filter, often effective. SSB is not overly difficult to manage
and I find the AVC-constant OK. A business-like audio, though at times
one misses the 8 kcs filter of the R-390A. Amazingly accurate scale, it
seems equivalent to a length of about 85 yards.


Handling this receiver, one can understand why the DOD , on the strength
of its early version from 1949, asked Collins to create the R-390x, which
admittedly are a cut above it in complexity, materials and performance
under extreme conditions. Still, the 51J-4 leaves my wrist feeling a lot
better, has the right filters and it is a great looker. (and it weighs
less than two-thirds of our favorite BA) 


How many were produced? 6-7000? Compared to 55.000+ of the R-390A?
Perhaps we ought to make a caucus of 51J-4 owners if there isn=92t already
one.(OK, make that 51J-*/R388* owners). Seriously, I would very much like
to gather any advice, any lore available about this enjoyable set. I know
there are a number of active people around like Jose, Dallas, W3AKEY,
Martin Boesch, Dave Knepper, - and likely many others. It is difficult to
get relevant articles from the newsletters, because they rarely seem to
make it over the Atlantic. If anyone can help I would  be very
grateful for that.   I also seem to recall that there were two
types of Kcs knob, was it improved in later s/n, did people switch it
from the 75A-4,  and what other changes were made over the course of
production (1957-1963)? Were the R-388A manuals more detailed than the
=92civilian=92 version? (which is good)





Best, 


Clemens


Clemens S.Ostergaard

Stadion Alle 52

DK-8000 Aarhus

DENMARK

+45 8611 0018


BA=92s:

R-390A/URR Teledyne Systems Corp 37856-PC-63 s/n 3821 

R-390A/URR Motorola 363-PH-54 s/n 1155 

R-390A/URR Electronic Assistance Corporation    
-60    s/n 1435
Hammarlund SP-600 JX-17 s/n 17566 

Siemens 745 E 310a  s/n 9/958974 
R-439a/ SRR 11, Magnavox Company, s/n 202 

Collins 51J-4 s/n  3026. 







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