[ARC5] Fun with the DU-1

[arc5 at ix.netcom.com]

Got a chance to work on my DU-1 Navy direction finder.
I'm sure most of you recognize it:

http://home.netcom.com/~arc5/DU1/DU-1.jpg

Cleaned it up, touched-up the cosmetics, lubricated, 
De-Oxit-ed where needed etc. and it fired right up
into my service monitor.
This one is jumpered for 12-volts.
Very impressive engineering.  While it is speced
for 200 volts B+, this little honey was still pulling
BCB stations out of the noise and DFing 
just fine with B+ all the way down to 12 volts.
In fact, I found no advantage at all to running 
the B+ any higher than about 45 volts.
Higher voltages made no difference 
in sensitivity or in noise floor.  

Interesting-  The manual specs the set for 200-1600 KC,
with an 800 KC test point in the middle of the top band.
But this set tunes and DFs all the way up to 3.3 MC,
with 800 KC in band #2.  
While I have not yet gone through the manual and 
inspected the components for changes, I can find no
evidence of ham-hacking (save one) that would indicate
someone munging the frequencies.  Since a common 
aviation freq at the time was 3105 KC, I wonder if
there was ever an official modification order.

The one ham-hack: the power connector.
Please take a look at this photo:

http://home.netcom.com/~arc5/DU1/DU-1bk.jpg

This set has had J-101 replaced with an octal male.
Given how many of these 5-pin-with-index plugs were
stripped out, there should be some in junk boxes around.
I had one, but sent it to a list member years ago.
The socket includes a black mounting plate that engages the 
matching plug's securing pin.  If anyone has one, I'm be grateful
and glad to trade or buy.  Also- (hope springs eternal) 
one of the scarce single-pin output connectors would put 
a smile on my face.

TNX OM ES 73 DE Dave AB5S