TS-1755A/GRM-55A

Test Set for the PRC-25 Military Squad Radio

©Brooke Clarke, N6GCE 2002 - 2010

Purpose

The GRM-55 Test Set is designed to stimulate the PRC-25 with RF and audio signals and to measure the signals present on the module test points. The results of each test appear as a go (green light) or no-go (red light). Included with the test set is a cable to allow accessing the audio and power lines of the PRC-25 POWER connector that also provides DC voltage to the GRM-55. The box on this cable also has a jumper plug like the one on the radio so you should be able to power both the GRM-55 and the radio using any external source that has the correct plug like a test adapter. There are no internal batteries.
A short BNC(m) to BNC(m) Cable is needed to use the GRM-55 but the lid does not have clips to hold one.

Box

Found a New Old Stock (NOS) on eBay Jan 2010. The box is marked on one face:
6625-973-2117 (i.e. the NSN)
TEST SET AN/GRM-55
1 EA SERIAL NO-120
A -10/72
WT 10 CU .6
YU-3X90
Insp 3355 343 BL6 CCA-3

and on the opposite face:
TM-11-6625-514-12
DTD 11/62 W/C1, C3
BILI FH6 DTD 0223

Packing List

Has the following info:

NSN	Description	Nomenclature
6625-973-2117	Test Set	AN/GRM-55
Consists of the Following:
5995-889-1019	Cable	CG-409G/U
6625-973-2118	Test Set Model: PL, A,B, C	TS-1755/GRM-55
6625-973-2119	Test Prod	MX-4622/GRM-55
6625-973-2120	Cable AY	CX-8593/GRM-55
TM-11-6625-514-12	Tech Manual
TM-11-6625-514-12 C1	Tech Manual Change
TM-11-6625-514-12 C3	Tech Manual Change
6240-542-6571	Lamp (3 each)	338

Operation

Maintenance

On test sets that have not been used for some time the rubber gasket between the lid and case sticks to the case when the lid is opened. To fix this clean the case lip and apply a light coat of silicon grease to the case lip and cycle the lid a few times.

Manuals

TM 11-6625-514-12
TM 11-6625-514-20P
TM 11-6625-514-45P

Use with other Radios

This test set should also work on the PRC-77 since the "POWER" and "ANT" connectors function in the same way and most of the module test points are the same. Has anyone done this?

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