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CPU L.E.D.'s
The CPU has three L.E.D.'s located on the upper left side of the board: D19, D20, and D21.
On game power-up D19 and D21 turn On for a moment then, 019 turns Off and D20 starts to
blink rapidly. D21 remains On. The system has detected a problem if the following happens:
CPU Board L.E.D. Error Codes
Center L.E.D. blinks one time
Center L.E.D. blinks two times
Center L.E.D. blinks three times
ROM ErrorU6
RAM ErrorU8
Custom Chip Failure U9
1 Beep
2 Beeps
3 Beeps
4 Beeps
5 Beeps
=
Sound Board Beep Error Codes
Upon Game Turn-On:
=
Sound Board O.K.
=
U9 Failure (RAM)
=
U18 Failure (ROM)
U15 Failure (ROM), if used
U14 Failure (ROM), if used
OPTO THEORY
The opto receiver (detector) should be approximately 0.1-0.7 volts when the opto beam is
unblocked and approximately 11-13 volts when the opto beam is blocked. The opto transmitter
(emitter or L.E.D.) should always be approximately 1.4 volts. Note, the transmitter (L.E.D.) is
larger than the receiver (it protrudes further from its case).
Transmitter
1.0-1.4 Volts
Receiver
0.1-0.7V Unblocked
11-13V Blocked
Green
o
WHT
Infrared Ray
Gray
Black
White
Green
DOCTOR WHO 1-47