Background

The RT-1319 is used to make the PRC-113 manpack radio and it can also be used as part of the PRC-240 mounted in an M998 or M1038 HMMWV along with a KY-57, VRC-83 is just the RT-1319 and this RF amp, GRC-206 is a four radio system that includes two VRC-83 systems w/KY-57, one for VHF AM radio and the other for UHF AM radio.

So far most of the manuals seem to be titled VRC-83.

Description

This is a dual band RF power amplifier that works with the RT-1319 to amplify either the VHF AM aircraft band or the UHF AM aircraft band.  It has a panel that looks like the battery box for the PRC-113 radio with two battery sockets to provide DC power to the radio.  The radio front panel antenna connector has a jumper that goes to the AM-7176 front panel so the AM-7176 has a T/R (transmit/receive) switch inside.  There is also a loud speaker in the AM-7176.

In Fig 3 below there is a green sticker that says:
"Warning, Remove batteries prior to shipment or active storage of 30 days or more"  That implies that there is an internal keep up battery.
Note: there are no BA-5590 type batteries in this system since the AM-7176A supplies "battery power" to the RT-1319 by means of connectors J4 & J5 that look like battery sockets.

Photos

Fig 1 Front Panel J5 & J4 Battery eliminator RF In, Antenna & J7	Fig 2 Rear J3 24 VDC Input	Fig 3 Side view, carry handle
Fig 4 Bottom Cover Removed 9V 65 mAh Ni-Cad battery	Fig 5 Front Panel J7 External Speaker and 5V keep alive	Fig 6 External Power Cable for J3 on back CX-11173/U (4ft 0in) MS3116-J12-3S A: Chassis (white) B: +24VDC (green) C: 24VDC return (black)
Fig 7 J3 Power Jack on rear Top pins are A & C (Ground) Bottom pin is B (+24 Input)	Fig 8 to remove finned assembly: * loosen 6 each hex bolts w/ 3/16" driver, * loosen 4 flat head screws holding DB connectors, * use 5/16" ignition wrench to loosen SMA connector at J1 * Pull off other coax near J1	Fig 9 Inside A2A2 main chassis A2A2A5-C1 is input filter cap A2A2A5-C2 is output cap
Fig 10 View of A2A1 finned assembly	Fig 11 Chassis top PCB, loosen only black screws	Fig 12  Loosen black screws on metal plate, Pull coax under plate to disconnect and the completely remove plate (has 9V battery attached).
Fig 13 Loosen black screws on top of the A2A2A5 input DC Filter assembly and fold upside down.	Fig 14 A2A2A5 input DC Filter assembly now accessible. Note black connector on red & black wires.  It connects to the A1 board on the A2A2A5 input DC Filter assembly	Fig 15 A2A2A5 input DC Filter assembly The A1 board is standing up in the upper left.  It has a header for the 9V battery input.  Metal can is L1 (1mH choke) -802 has the A1 battery board. C1 short Cap on left, C2 long Cap on right.
Fig 16 A2A1A3 Hybrid Coupler Assembly	Fig 17 A2A1A3 Hybrid Coupler Assembly	Fig 18 A2A2A2 Control Board
Fig 19 A2A2A2 Control Board	Fig 20 Troubleshooting DC Input Short Hand Drawn DC Input Circuit & ESR-Cap meter readings.	Fig 21 after mating the finned assembly & chassis 4 connections: 2 each DB-9 and 2 each coax.
Fig 22 A4 Power Supply PCB side A1J1 (2x5 header - missing pin #1) on PCB Outputs: +24 Reg Pin 2, 4 Gnd Pin 3,5 -100 V Pin 6 +5V Pins 7 & 8 +12V Pin 9 -12V Pin 10	Fig 23 A4 Power Supply Heat Sink side A2J1 (DB-9m) on heat sink +24V In Pins 1, 2 6 Gnd Pins 4, 5 & 9 +24 Out Pins 3, 7 & 8	Fig 24 Chassis w/o A4 Power Supply
Fig 25 External +24 to A4 Power Supply Black wires = Ground White wires = +24 In	Fig 26 A4 Power Supply Broken Resistors R21 (100R) & R22 (100k)just below U1 (555 timer) are broken off. U1 was not powered, VR1 OK, tracing path found these. Also broken in Fig 22. The actual R22 value is 75k, not 100k.  The actual R21 is 100 Ohms.	Fig 27 After repairing A4 PS But missing the RF Coax. Fault lamp most likely due to missing coax between RT & Amp. The cable is BNCm - BNCm, maybe: NSN: 5995-00-823-2985 SM-D-415563-2Ft Note:  The Donkey Dick antenna will NOT fit on the Type-N panel connector.

Connectors

AM-7176		RT-1319
J1
J2
J3	24 VDC In (Fig 6)
J4	Battery DC out
J5	Battery DC out
J6
J7	5V Keep Alive External Speaker

Cables

VRC-83 ID	Description	End	End
W1	DC Pwr	AM-7176-J3	Vehicle Batt Spade Term
W2	RF	AM-7176-RF_In	RT-1319-Ant
W3	Crypto	KY-57	RT-1319-Audio
W4	Memory	AM-7176-J7	RT-1319-Remote

Controls & Indicators

Bypass or Power Amp toggle switch
Fault warning lamp
Speaker Volume
Power On/Off
RF IN (from RT-1319 antenna connector)
ANT to VHF/UHF antenna
Front panel speaker
J7 external memory power supply.

Problem

Shorted DC Input

This unit came DOA (I knew that at the onset) with the symptom of blowing a breaker.  My hope is that it can be repaired without detailed documentation.
After removing the finned assembly which contains the DC input filter and RF power amp, the resistance between J3-B (+24VDC) and either J3-A (chassis) or J3-C (-24VDC) shows as OL (Over Load) so the problem is not in the finned assembly. 

The next most likely place is the Input DC Filter assy (not the EMI filter on the back of J3).
C1 and C2 can be measured with the ESR-Cap meter with the power supply as is.
C1= 0.24 Ohms - 1530 uF [s.b. 01132U050AK - 1300uF 50V] so looks OK
C2= 0.00 Ohms - 1720 uF (Fluke 87V DMM shows falling resistance not short) ESR meter now reads 0.40 Ohms - 1720 uF [s.b. 101172U100AJ2A - 1720 uF  100V] so OK
So, the above two caps seem to be OK.  They are in the DC power supply Input Filter assy that contains CB1.
The power supply is connected to the chassis and to the two printed circuit boards above it, so they will need to be removed to get it out.
See Figs 11 to 19 above.  Only back off the black captured (+) screws.

With the Fluke 87 V DMM in diode mode (black to ground) it reads 1.1 V at C1+ and 1.0V at C2+ with power switch on or off.
Something is bad on the A2A2A5 input DC Filter assembly.
It looks like the 2N685 SCR or the 1k resistor from Gate to Anode (ground).  The resistance measures 37 Ohms.
Using the ESR-Cap meter on the SCR side of choke L1 shows 0.48 Ohms but on the C2 sice of L1 shows 0.00 Ohms ^ 1720 uF.
That's strange.  So I opened one of the connections on C2 and the circuit and C2 both look good.  I think the problem was a short between one of the black wires at the top of C2 and the other terminal of C2. After reassembly the current draw is 0.042 A not the 1+ amps it was.
-----
Note when reassembling First connect the molex connector on the 9V battery wires to the A1 board on the A2A2A5 input DC Filter assembly.
When the A1 assembly is complete and before installing the A1 finned assembly applying 24 VDC to C2 results in about 62 ma of current.
Prior to placing the finned assembly into the chassis, position the chassis with the bottom side down and the opening on the edge of a table facing you.  That way the flex cable and DB-9 connector will be held by gravity in the proper place.  If the chassis is in some other position the connector may be trapped.

For a discussion of the troubleshooting method see the ESR-Cap meter web page.

No Regulated 24 VDC on Battery Sockets

R21 (1oo Ohms) & R22 (75k Ohms) next to U1 have been broken off.  Replaced with single 100 Ohm and series combination of 56K + 22K = 78K Ohms.
Now with 26 VDC input the A4 assembly (no output loads connected) draws about 700 mA.  The cases of the power transistors show about 40 kHz.
The 2x5 post header has the following voltages:

-13	+6.5	-101	+26	+26
+13	+6.5	0	0	X

Manuals

TO 31R2-2VRC83-1-1 Supplemental Operator's Manual, Radio Set AN/VRC-83(V)2, p/n 707123-803, 15 March 1985

TO 31R2-2VRC83-1 Operator's Manual, Radio Set AN/VRC-83(V)1, p/n 707123-801, 15 March 1985

TO 31R2-2VRC83-2-1 TM w/Supplemental Maint. Inst, Ill Parts Breakdown (IPB), Intermediate Level, Radio Set AN/VRC-83(V)2, p/n 707123-803 & 707123-805, 16 July 2013

TO 31R2-2VRC83-2 TM Maint Inst w/ Ill Parts Breakdown (IPB), Intermediate Level, Radio Set AN/VRC-83(V)1, p/n 707123-801, 31 Dec 2008

TO 31R2-2VRC83-3-1 TM Supplemental Maint Inst, w/ Ill Parts Breakdown (IPB), Depot Level, Radio Set AN/VRC-83(V)2, p/n 707123-803, NSN 5820-01-127-3485 and p/n 707123-805, 30 March 2014

TO 31R2-2VRC83-3 TM Maint Inst w/IPB, Depot Level, Radio Set AN/VRC-83(V)1, p/n 707123-801,NSN 5820-01-108-6622, 26 March 2014

TO 31R2-2VRC83-6WC-1-1 TM Supplemental Sched Peroidic Inst Workcards, AN/VRC-83(V)2, p/n 707123-802 (ATOS), 1 Oct 2003

Incomplete without TO 31R2-2VRC83-6WC-1
Incorporates TO 31R2-2VRC83-6WC-1-1 dated 28 Feb 1995

TO 31R2-2VRC83-6WC-1 TM Sched Periodic Insp Workcards, Radio Set AN/VRC-83(V)1, p/n 707123-801, 1 Oct 1984

Incorporates Supplement TO 31R2-2VRC83-6TP-1 dated 26 Feb 1995

TI-08946A-35/I Installation of UHF Radio Set, AN/VRC-83(V)2, in Radio Sets, AN/MRC-138A & AN/MRC-138B, 4 Jun 1006

Test Sets (all test sets & manuals WANTED contact me)

Nomenclature	Name	Magnavox p/n	Manual	Description
TS-4090/GRC-206(V)	Power Converter Test Set	812540-801	TO 33DA27-17-1	pots and switches, no meters & 2 cables
TS-4091/GRC-206(V)	Receiver Test Set	812539-801	TO 33D27-36-51-1	speaker, switches, pot & 2 cables
TS-4093	Transmitter Module Test Set	812542-801	TO 33D7-33-191-1	3 meters & 3 cables
TS-4094/URC	Multi-Module Test Set	812541-801	TO 33D7-33-190-1	5 meters & 6 cables
OF-118/U	Test Adapter		TO 33D7-50-755-1	3 adapter boxes & 8 cables in suitcase
MXF-220-1	Adapter/Power Supply	901450-801	Wanted	see below

Magnavox MXF-220-1 Power Supply and Watt Meter

This is an axillary piece of equipment to be used with the AM-7176 typically in a base station.
Came from American MilSpec.

My RT-1319 came from the UK and I expect that this unit is also from the UK because in Fig 2 below you can see it's setup for 220 VAC.
Maybe there's a jumper change that will make it work on 115 VAC.

Controls, Indicators & Connectors

Y-cable (upper left) that connects to the RT-1319 REMOTE and AUDIO connectors.
Amplifier RF Nm - goes to AM-7176 RF In
Pilot lamp with "press to test"
Power toggle switches for AC and DC
1/4" phone jacks for RECord and MICrophone
Monitor Switch: XMT AUD, REC AUD, REFL RF, FWD RF, AMPS, VOLTS
ANT Nm to ANT on AM-7176
Local Remote Control toggle switch
CONTROL connector -?
AUDIO (6-pin U-229 type)

Fig 1

Fig 2 note: 220 VAC sticker

Fig 3 Photo 3 had wrong cable connections Photo 4 should be correct.

Related

Links

Back to Brooke's Products for Sale,  Military Information, U229 Audio Accessories, Audio Connectors, Electronics, Personal Home, PRC68.com Contact, Alphanumeric Index to web pages

Page created 23 Sep. 2014.