[Milsurplus] "Sick" R390/URR

[WA5CAB at cs.com]

John,

The first thing that you should always check in the R-390 and R-390A is the 
mechanical alignment of the coil tuning racks.  And especially in the 
relatively rare R-390.  To mechanically align an R-390A, you set the band switch to 4-8 
MC and turn the tuning up to 7999+.  And all of the alignment marks on all of 
the cams should match up.  The R-390 isn't done this way.  You do each slug 
rack on its own band setting.  If you do the 390 the way you do a 390A, you get 
a receiver with a few hot spots, mostly deaf and partially dead.  The reason 
I know this is that during an ocean vacation cruise in 1967 and 1968 I was for 
a thankfully short period responsible for the care and feeding of about 92 
R-390A's.  A few years after I came home, I acquired an R-390 and the first 
thing I did was the mechanical alignment since everything was "way out of 
adjustment".  Then I read the TM which I had also acquired and discovered that the 
similarity between the two receivers is mostly only skin deep.

There are several other problems that could explain your reported symptoms 
but that's certainly the first one I would check as I'm probably not the only 
Navy tech to have made that mistake (the R-390 was mainly an Army set).

In a message dated 3/23/2008 6:56:39 PM Central Standard Time, 
k5pgw at yahoo.com writes: 
> Hello Folks!! I have been tinkering with a Collins
> made R390/URR for several days now and am not making
> much progress. I have had it on the shelf for about 20
> years.  
> 
> I have removed all connectors and applied De Oxit . I
> have removed all tubes and treated the tube sockets
> with De Oxit. I have done some tube swapping with
> little result. I have not chanced the 6AJ5 because I
> don't have one. I feel like the receiver is deaf
> compared to other receivers I have such as KWM 2 and
> several Drakes.
> 
> It receives after a fashion but has low sensitivity
> and amplification within the receiver. It works on the
> AM broadcast band with "not very loud" audio. I am
> using a 70volt line transformer to 4 ohm Hammarlund
> speaker. I copy a few CW signals on 160 meters and CW,
> AM, and SSB signals on 80 meters. The shortwave bands
> in the 6 mhz and 9 mhz are received fair. I get weak
> WWV signals on 5, 10, 15 mhz. I hear nothing above the
> 12 mhz shortwave bands that I consider receiving a
> useful signal.
> 
> I don't know the heterodyne scheme so I don't know if
> various bands just aren't there because of hetrodyne
> problems.
> 
> My "gut" feeling is that the RF stage isn't working
> correctly as well as "some bands just aren't there"
> for some reason or other.
> 
> If you have experience with the R390/URR and have
> encountered these symptoms, I would greatly appreciate
> your suggestions and guidance. Thanks for reading. 73,
> 

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at comcast.net> (Backup email)
   
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