Error in Applying MWO 11-5820-477-30/1

TM 11-5820-477-30

2-17. Error in Applying MWO 11-5820-477-30/1

a. Instructions in MWO 11-5820-477-30/1 (Modification of Radio Set Control Groups AN/GRA-39 and

AN/G RA-39A to Improve Communications When Used With Radio Set AN/PRC-25 in Squelch Mode, 11 April

1967, which was rescinded by DA Cir 310-25,6 Oct. 71) assumed a wiring condition on TEL-REMOTE-RADIO

switch S102 of the C-2329/GRA-39 and C-2329A/GRA-39 that did not exist on all units. After performing the

MWO on some units, the operator could not communicate with the other control unit when switch S102 was in

TEL position.

b. There is a jumper between terminals 4 and 9 of S102A (rear) in some units and not in others. A blue-white

wire is connected between terminal B of AUDIO receptacle J101 and terminal 4 of S102 A in some units and to

terminal 9 of S102A (rear) in other units. The MWO removed the jumper wire and connected a 560-ohm resistor

(RI 23) between terminal B of J101 and terminal 9 of S102A (rear). In units where the blue-white wire ran to

terminal 4 of S102A, the equipment performed correctly; in units where the wire ran to terminal 9 of S102A,

telephone communication between operators of control units could not occur.

c. To determine whether units C-2329/GRA-39 and C-2329A/GRA-39 were modified correctly, make either of

the following tests:

(1) Set the control switch to TEL. Make a resistance measurement between terminal B of AUDIO receptacle

J101 and terminal B of RADIO receptacle P101. It should be 560 ohms (R123). If it is O ohm, the MWO was not

applied or it was done incorrectly.

(2) Perform an operational test as follows:

(a) Connect field wire between the remote and local control units and set the control switches to TEL

position.

(b) Using the handset connected to the AUDIO receptacles, communicate between the two units. If the

local control unit operator has no sidetone and cannot hear the remote control unit operator, the MWO was

performed incorrectly.

d. To repair equipment that fails the tests (step c. above), proceed as follows. (Refer to figure 2-18.) Inspect

switch S102A (rear) to determine if the blue-white wire from terminal B of J101 is connected to terminal 4 or 9 of

S102A (rear) (A, figure 2-18).

(1) If the wire is connected to terminal 4 of S102A (rear), do not disturb the blue-white wire, but cut the

jumper from terminals 4 and 9 of the switch. Connect a 560-ohm resistor (NSN 5905-00-682-41 09) (same as

resistor R115 in TM 11-5820-477-35P) between terminal B of J101 and terminal 9 of S102A (rear) (B, figure 2-18).

Put insulation sleeving on the resistor leads.

(2) If the blue-white wire is connected to terminal 9 of the switch, DO NOT REMOVE THE JUMPER FROM

TERMINAL 4 OF THE SWITCH. Instead, remove both the blue-white wire and the jumper from terminal 9 of the

switch. Strip 3/8 inch of insulation from each wire, splice the two wires together, solder them, and insulate the

splice with electrical tape (C, figure 2-1 8). Connect the 560-ohm resistor (NSN 5905-00-682-4109) between

terminal B of J101 and terminal 9 of the switch.

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