[Milsurplus] OA-65AMRC-2 Receiver

[WA5CAB at cs.com]

Joe,

OA-65/MRC-2, including O-59/MRC-2 and RA-20-B, is covered in Change 1 to TM 
850, and dated 02 June 1952.  The change is 70 pages and 4 foldouts (about 
the size of one of the BC-348 series manuals).  Price by itself $20.00 plus 
$3.50 shipping.

TM 11-624 on AN/MRC-2(*) shows a little bit on the OA-65 but for 
maintenance refers to TM 11-850 (09/03/46) with Change 1.

The only tips I can offer are that the Channel A receiver differs from the 
BC-342 it was converted from in having an added connector on the back with 
center contact wired through a 2.2 Meg resistor to the cathode of the HFO.  
Plus there are a number of component value or type changes in the oscillator 
and mixer stages of importance only if you need to replace them (including 
changing the tube to a 6J5).  Also, an IF output connector is added to the 
2nd IF stage.  The Channel A receiver will run standalone.  The Channel A 
receiver's HFO is connected to the Channel B receiver's mixer through O-59.

The Channel B receiver will not run standalone (without O-59 and the 
Channel A receiver).  The same changes were made to the mixer and 2nd IF stage but 
as far as I can find in the text, the only change to the HFO stage is the 
removal of the tube and the cathode resistor R42 and the addition of a 
connector (octal) plugged into the tube socket and wired to a connector added on 
the rear of the receiver.  To run the Channel B receiver standalone (for 
general maintenance other than alignment), you would need to make a plug-in 
adaptor from an octal tube base and socket and wire R42 into it.  And use the 
original type 6C5 tube.

In a message dated 05/26/2012 15:46:23 PM Central Daylight Time, 
joeconnor53 at yahoo.com writes: 
>    I've had this receiver for about 10 years and it has been on my to-do 
> list since then. I worked up the nerve to tackle after having just 
> disassembled and recapped a BC-342 and a BC-344. (Man, they sound so much better 
> with all the leaky Micramolds out of the under-chassis cans).
>  
>     This set has the rather interesting RA-20B power supply. The exterior 
> is in pretty clean shape. The interior, however, is a mess. It's gonna need 
> work. I've been told this is an unusual receiver so I want to restore it 
> right.
>  
>      1. Does anyone have a source for the manual for this set or a copy 
> they could scan for me? From what I can gather, the manual is TM 11-624. I 
> can't find it from any of the usual sources. From just a cursory look, I can 
> see that the RA-20B power supply is radically different from the RA-20. I 
> see some disconnected wires and what may be some ham mods (which I would 
> like to undo)
>  
>  
>      2. From what I can see, I am missing the following parts:
>  
>       a. The "snout" from the front panel;
>  
>       b. The BFO assembly cover;
>  
>       c. The "toilet-seat covers" for the front panel jacks. 
>  
>       d. The dial cover and tuning indicator.
>  
>       e. The vernier lock.
>  
>     If anyone has any of these missing parts and would like to sell them 
> to me, please contact me.
>  
>  
>     3. Have any of you worked on these sets? If so, do you have any tips 
> or suggestions?
>  
>  
>     As always, thank you for your help and guidance.
>  
>  
>                             Joe Connor
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480