Kenwood Th 75e Manual Arts
Service Bulletin no. 957 (9-1-1990) When the TH-75A is connected to a vehicle battery, ignition or alternator noise can be induced on the DC line. When the transceiver is in the automatic battery saver mode, the noise pulses overcharge C348 on the RF board causing it to short. The supply current opens L218 and the foil trace at this coil.
Legacy Vista Blood Bank here. To protect the transceiver, a Zener diode will be used to clamp the SBR line. The Zener should be solder between the SBR side of L218 and the shielding case of L221 on the component side of the RF board (X53-3370-11) (A/3).
Modifications for the Kenwood TH-75. The Service Manual disassembly instructions will be. Some TH-75A owners have reported that the transceiver intermittently.
The Service Manual disassembly instructions will be required to perform this modification. Note: This modification has already been performed on models stating with serial number 007xxxx. Required part: 22V Zener diode (UZP-22B) This is an optional change that is not covered under warranty.
Time to perform this modification is 1 hour or less. Author: Kenwood Communication, inc. Service Bulletin no. 978 (8-8-1990) Some TH-75A owners have reported that the transceiver intermittently loses its memory channel information after transmitting. Other users have reported symptoms such as key board lock up after transmitting. The following modification will re-configure the PTT input to the microprocessor to correct these conditions. Required parts: 33 Kohm chip resistor RK73GB1J333J 470 pF ceramic capacitor CK45B1H471K PTT tactile switch S40-1415-05 • Disconnect the battery and antenna.
• Remove the three case screws and two battery plate screws. • Lift the front panel from the body of the transceiver and disconnect the two flex cables. To open the connectors push the tabs towards the flex cables and gently lift up. • Remove the 4 screws from the Control board inside the front panel. • Remove the 3 screws from the speaker mount. • Carefully lift the Control board, PTT switch assembly, speaker, and mic element from the front panel.