MRC-67A Amplifier-Speaker

Brooke Clarke 2011
MRC-67A
          Amplifier/Speaker


Background
Connectors
Wiring
Mounting
Patents
Links

Background

When a radio that works fine as a backpack is used in a vehicle an amplified speaker is needed.  Many of these are designed for a specific radio system and others like the MRC-67A is a Commercial Off The Shelf (COTS) product that has general applicability.

I got these one because it has a broken connector so needs a repair and some reverse engineering.

There are two volume controls, one for the loudspeaker and one for a handset like the H-250.  I haven't tested it, but I've read that when the DC supply is off the handset is directly connected to the radio and will continue to work.  For mobil ops it may be easier to use the M-80 microphone.

MRC-67A
                  Amplifier-Speaker w/Broken AUDIO connector
MRC-67A
                  Amplifier-Speaker w/Broken AUDIO connector





Controls & Connectors

ON/OFF

Toggle switch

HANDSET

U-229 type audio

POWER

Chassis: 2 mail pin
Cable: MS3116 F8-2S
A: +10 to 36VDC
B: Gnd

V
ma
10
43
24
19
36
15

AUDIO

Chassis: MS3114 E10-6P
                (PT07A-10-6P)

Cable: MS3116 F10-6S

Color
Desc
U-2291
A
Grn Gnd
A
B
Blu Audio In
D
C
Yel PTT
C
D
Vio Audio Out
D
E
Red +DC Pwr
n.c.
F
Blk DC Gnd
n.c.
Note 1: cable for use with most radios.

Handset Volume

Top knob

Speaker Volume

Bottom knob

Green LED

DC Power good

Yellow LED

Receive Audio Present

MRC67 broken AUDIO
                  connector MRC67 broken
                  AUDIO connector

Wiring

Speaker Enclosure

2x6 Socket P1 connects to:

P1-
1
3
5
7
9
11
2
4
6
8
10
12

Red
Vio
Blu
Grn
Blu
Blu
Blk
Yel
Grn
Yel
Vio
Viio
Speaker
S





S





Green LED
L





L




Yellow LED

L






L


Handset Vol


H
H





H

Speaker Vol




SV


SV


SV

Chassis Enclosure

2x9 Socket P2 connects to:

P2-
1
3
5
7
9
11
13
15
17
2
4
6
8
10
12
14
16
18

Grn Red
Vio
Grn
Yel Blu
Blk
Blk
Brn
Blu
Vio
Yel
Gry
Vio
Org
nc
Red
Red
On/Off

A2


A1


BC



AC

B2



Handset (E, F: nc)
A
B








D
C





Power






B









A
Audio


A
C
F


B



D


E


On/Off
A1: Blu
B1: nc
AC: Gry
BC: Brn
A2: Vio
B2: Org

Amplifier

Speaker Jack J1
Chassis Jack J2

Mounting

There are 4 captured screws in the very corners that hold the two chassis boxes together.  They are either 6-1.0 x 35mm or 1/4-28 x 1-3/8" (the screw fits both metric and English screw checkers).

These screws do not fit the two tapped holes (see Controls & Connectors above) on the face where the connectors are located  or the two tapped holes that are directly opposite them.  They may have a center to center distance of 73.675mm (2.900").
These two tapped holes are for a "U" shaped mounting bracket that's held in place by a couple of thumb screws.  See photo on the Ultralife MRC-67 web page.

On the bottom there are four 7.2mm (0.283") I.D. clearance holes in a rectangular pattern that's 82mm (3.23") wide x 106mm (4.17") high.  The idea is to remove open the two boxs and install mounting bolts to hole the connector (rear) box to a bulkhead then reinstall the speaker (front) box.

Patents

The back of the speaker has these patent numbers:
3898393 Magnet Centering Device and Shield, C.B. Digre, Aug 6 1975, 335/231; 381/420
4293741 Magnet Assembly, C.B. Digre, Oct 6, 1981, 381/420; 335/231; 381/189; 381/396

Links


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page created Nov 18, 2011.