Tandy 102 Service Manual page 49

3. Key doesn't function
3
Check if the keyboard connector is correctly connected.
Check the key scan signal.
Is the scan signal present at M25 PAO - PA7 and PB1 ?
(If not, check if pulses are emitted from the TP terminal (pin 10) of M18 and M25 at 4
msec intervals.)
Check the diodes on keyboard.
Check the return signal.
Check M15, M3, M26, M16 and pull-up resistors R163 - R170.
Check the key switching no-input keys.
END
4. Buzzer doesn't function
4
No melody is heard.
YES
NO
Check the connector connections.
• Check if the LCD connector is correctly connected.
• Check if the buzzer connector on LCD PCB is correctly connected.
Check the buzzer control logic.
Check M26 and M25 (PB5 port, TO terminal).
Check the buzzer.
END
5-5