TR-7800 Optional continuous charge for internal batteries
The internal batteries for memory back-up charge only when the radio is on. If the radio is used less than 2
hours a day, the internal batteries may not charge sufficiently to retain memory if the main power is disconnected. This
optional change may be made to continuously charge the internal batters from the main power source, whether the radio
is on or off.
Procedure
On the RX unit X55-1270-10, change R94 from 56 ohm to 120 ohm, ½W. Cut the foil at the input to Q27 and connect via
a 3/4" lead to the BB terminal on connector 1. Battery charge current will be 15mA nominal.
Note:
The radio should be connected directly to the vehicle battery and not through the ignition switch.
Turn the radio off before connecting or disconnecting the power cable.
For early units: Before closing the case, check clearance from the back of the battery case to the chassis.
If very close, add suitable insulation between the battery case and chassis.
Check for the presence of a 470 kohm 1/8W resistor which should be located on the bottom of the
Control unit X53-1180-xx, Connector 11, UP pin. Add if not already installed (and see Service Bulletin #829).
