[R-390] R-390/URR MWO's

[Ed]

Change 4 of TM 11-856, TO 31R1-2URR-154,  dated 22 Dec 1958,  indicated that 
" In receivers modified by MWO 11-5820-294-35/1, the wires connected to B+ 
3/8A Fuse F102 are removed and tied together, and the ground connection on 
transformer T801 is removed.  There is no connection between the DC 20A Fuse 
F103 and P118-15 (not applicable to Fig 53 of TM), and Terminal 6 of T801 is 
connected through the contacts of J818-15 and P118-15 and B+ 3/8A Fuse F102 
to ground.  The B+ 3/8A  Fuse is called the HV 3/8A Fuse.

Power Supplies PP-621/URR modified in accordance with MWO 11-5820-294-35/1 
are NOT interchangeable with power supplies that are not so marked because 
of wiring changes in the B+ 3/8A Fuse F102 circuit.

R-390/URR Receivers modified by MWO -35/1 above have the former B+ 3/8A Fuse 
F102 in the ground lead of power transformer T801 and the name of the fuse 
is changed to HV 3/8A.  The MWO -35/1 supersedes MWO SIG 191 dated 20 July 
1955 and contractor changes on Power Supplies PP-621/URR identified as MOD 1 
and above.  These changes restore interchangeability between Power Supplies 
PP-621/URR and permit their being used in all Radio Receivers R-389/URR, 
R-390/URR, and R-391/URR so modified.

In receivers modified by MWO -35/1 above the B+ 3/8A Fuse F102 is NOT 
connected between P120-5 and +300V Unregulated.

In power supplies modified by MWO -35/1 above there is NO connection between 
Terminals 10 (Ten) and 6 (Six) of T801; There is a wire connected between 
Terminal 6 of T801 and Terminal 15 of J818.

On Receiver Main Frames modified by MWO -35/1 above, ( TM Fig.106) Station 
35 Wire 1-33 is 7-40,  Wire 5-41 is 15-41 and B+ is HV .  At Station 37 
there is NO Wire 15-41.  At Station 41 there is a wire added between the 
cable and Terminal 1  of C101 labeled 5-41, change  Wire 35-1 to 42-2, and 
Wire 37-2 to 35-1.  At Station 40, add a wire between Terminal 7 and the 
cable labeled 35-2."

Perhaps some other group member might bring up details for other R-390/URR 
MWO's, such as: 11-5820-294-35/2,  11-5820-294-35/3, 32-5820-134/2, 
32-5820-134/3 and any other pertinent MWO's.


73, GL DE
KD6EU
Ed Alves
USA