Talkback Removal; Mod #1 - The Relay Approach - PRESIDENT LINCOLN Modification Manual

Talkback Removal

MOD #1 - The Relay Approach

One method of Talkback removal is to break the speaker line with a relay.
Parts needed :
12Volt SPDT relay
2 - 1N4148 Diodes
1 - 1N 4001 Diode
Several pieces of hookup wire
Jumper the Relay coil - K1 with a 1N4001 Diode - D1. To key the relay you connect one side of the
Relay coil (the side with the Cathode of the diode) to IC107 pin 1.(HA17808W)
Cut the Blue wire that goes to pin 1 of the AUX plug on the rear of the radio. (Make sure you leave
enough wire to reconnect each end to wires for the relay.) Attach the wire from pin 1 of the AUX plug
to the Wiper contact of the Relay- K1. Attach the other half of the Blue wire to the Normally Closed
side of the Relay.
(Make sure you leave enough wire to reconnect each end to wires for the relay.)
Cut the Yellow wire from pin 3 of the Mic plug. Jumper the cut Yellow wire with a 1N4148 Diode - D2
(Cathode to the Mic Plug Pin 3) Connect the last 1N 4148 Diode - D3 to the Relay coil, Anode side to
the Anode of the Diode - D1 on the coil of the relay.Connect the Cathode to Pin 3 of the Mic
plug.(Cathode to Cathode of the two diodes on pin 3 of the Mic plug.)
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