Trickle Charge For Backup Battery; Single Antenna - Kenwood TKR-750 Service Manual

2. Trickle Charge for Backup Battery

If the external DC power supply is connected to the Main
DC connector and a backup battery (12V rechargeable type) is
connected to the Backup connector at the same time, the
battery can be trickle-charged from the external DC power
supply with a maximum current of 0.5A.
Short the CHARGE land near R61.
Notes :
1. Make this modification after removing the DC power sup-
ply and battery for safety.
2. When the DC power supply is connected after the modifi-
cation, DC voltage is output to the Backup connector. Be
careful during setup.
3. When the backup battery is used for a long time, remove
the battery from the repeater and recharge it because the
trickle charge is not sufficient for recharging a completely
discharged battery.
CN7 BACKUP
(ORANGE)
CHARGE
Fig. 2
MODIFICATION
Final unit (A/2)
Component side
K1

3. Single Antenna

The TKR-750 can be used as a base station by sharing an
external antenna connector for both transmitting and receiv-
ing data.
3-1. Modification
1. Change the installation position of C92 and C160 of the
final unit using a soldering iron.
Final unit (A/2)
Component side
ANT SW
CN3
REV
Fig. 3
2. Short-circuit the printed pattern of ANT SW near the CN3
connector by soldering.
3. Disconnect the pin connector from CN18 of the TX-RX
unit.
Remove the two screws used for securing the BNC con-
nector on the back panel of the unit. Detach the antenna
cable assy. (E30-3418-05)
4. Cut off the coaxial cable of the removed antenna cable
assy on the BNC connector side.
Strip off the insulation of the cut-off coaxial cable to pre-
pare it to be soldered.
About 20mm
About
8~10mm
Strip off the insulation so that
the cable can be soldered.
Fig. 4
TKR-750
C160
FWD
C92
RX
CN53
E
Cut off the coaxial cable
at this point.
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