Comnet LBI-38435B, Maintenance Manual

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LBI-38435B
14
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Receiver Voltage Readings
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IC and Chip Component Replacement
Procedures
Also provided in the Maintenance Manuals for each
circuit board are IC DATA SHEETS with information
about each IC package used on that particular circuit
board.
DTMF MICROPHONE MODIFICATION
1. Remove the top radio cover and locate the
System Control/Synthesizer board (A801).
2. To isolate J701-1 from the printed board,
carefully cut the zigzag run on the component
side of the board near capacitors C613 and C615
(see Figure 5).
3. Solder a wire (#24 AWG) to J701-1 on the
component side of the board.
4. Solder the other end of this wire to the output of
the 9-Volt Regulator IC207, pin 3. Pin 3 of
IC207 is the pin nearest the rear wall of the
radio.
5. Locate the connector plug on the DTMF
microphone and insert the blue wire in P701-1.
6. If an external speaker is desired with the DTMF
microphone, perform the following
modifications:
a) On the Transmitter/Receiver board (A802),
connect jumper plug P502/P551 across pins
1 and 2 of J502/J551 (IN).
b) Verify that the internal speaker plug
P503/P552 is connected to speaker jack
J503/J552.
c) Locate the internal speaker in the front cap
assembly and cut the two wires from the
speaker terminals.
d) Solder two extension wires to these cut
wires and run the wires along the side wall
near the System Control/Synthesizer board
(A801) and through the opening around
J701 at the rear of the radio.
e) Add a connector to these wires and a mating
connector to the leads of the external
speaker.
f) Strain relieve the wires inside the radio with
a tie wrap at J701-8.
Figure 5 – DTMF Microphone Modification