Access to the LOGIC UNIT is required.
- Disconnect mains lead and antenna lead.
- Remove the EIGHT screws from the TOP COVER.
- Remove the FOUR side screws. (Two left & two right).
- Remove the top cover.
- Remove FOUR screws holding the PA/REG UNIT. (Two at top front & two at rear).
- Carefully hinge PA/REG UNIT back out of the way.
- Remove shield to LOGIC UNIT. (Unit on right hand side).
Refer to diagram above.
This modification is done to the LOGIC UNIT in three parts;
- Cut the red wire to J3
- Add a diode (small signal type ie; 1N914 etc.) between PIN 18 of IC5 74HC244 [ANODE END OF DIODE] and the CATHODE of D10 [CATHODE END OF DIODE]. The back-up battery may have to be carefully levered out of the way in order to gain better access to PIN 18 of IC5.
- Add a diode (small signal type ie; 1N914 etc.) between the pad where D25 CATHODE would go [CATHODE END OF DIODE] and the pad just opposite D20 CATHODE [ANODE END OF DIODE]. See diagram for details. (that's coming later)