Abbott aim Technical & Service Manual page 82

Section 6, Troubleshooting
Table 6-5. Troubleshooting
Symptoms Possible Source Troubleshooting (repair as required)
3. One or more keys on Locked keypad. Unlock keypad.
keypad inoperative. - - -
Keypad ribbon cable. Check that keypad ribbon cable is
plugged in properly to circuit board.
Keypad. Typical keypad failure causes one entire
row or column to be inoperative. Replace
keypad.
Keypad interface.
Check connector J3 and J14, and U18.
Check for keypad column strobes at
PBXO, PBX1, etc.
4, Motor won't turn or turns
at incorrect speed.
UMA. Check for output DC voltage change at
U11-1 as PWM duty cycle is changed at
U2E pin 11.
Current amplifier U23B and/or
associated components.
No voltage or too low a voltage at U23-7
output causes too slow a motor speed;
replace components as necessary.
U24. Verify that U24-6 pulses whenever U24-7
is less than 1.3V (approximately).
U28 or U27A. Both should be on when U24-6 is high
Summing amplifier U23A.
Verify that amplifier operates properly;
replace as necessary.
Comparator U25B. U25B-7 should be high when U24-6 is
high.
Transistor U13B. U13B should be off when U13-4 is high.
Transistor U34B. U34-5 should be on when its gate drive is
low; replace as necessary.
Comparator U25A. U25-1 should pulse low when U24-6
pulses high.
Voltage converter U22 or U22-5 should be -5V when motor drive
associated components. circuit is on.
Transistor U27B.
U27-5 should be low when U27-4 is high.
Motor. Replace motor.
430-600035-002 (Rev. 11/99) 6-16 AIM/AIM Plus Technical Service Manual