Brother LX-200 Service Manual page 122

Film Feed Detector Circuit
This circuit detects the film feed status to prevent jams if a problem occurs.
The film feed detector switch TPS is mounted before the paper eject roller and if
there's no problem with the film during document feed or compression, the film
presses against the film feed detector switch TPS and sets the ON (input Low).
Fig. 5.4-8
Input Voltage Detector Circuit
This circuit detects the AC adaptor output voltage to prevent danger due to an AC
adaptor that is faulty or incorrectly inserted.
The circuit detects high voltages using transistor Q7.
When the AC adaptor output voltage is below approximately 23 V, transistor Q7 is
ON. When +24V DC is applied to R80 and R81, port P66 of the main CPU becomes
approximately 4 V, and a High status is detected.
If the AC adaptor output voltage exceeds approximately 23 V, transistor Q7 turns
OFF and port P66 of the main CPU detects a Low status. As the normal output
voltage of the AC adaptor does not exceed approximately 23 V, port P66 of the main
CPU is normally at High status.
This circuit detects low voltages using ZD1 and transistor Q6.
When the AC adaptor output voltage exceeds approximately 16 V, ZD1 is
conducting and transistor Q6 is ON. Port P67 of the main CPU detects a Low
status.
If the AC adaptor output voltage drops below approximately 16 V, ZD1 becomes
non-conducting and transistor Q6 turns OFF. Port P67 of the main CPU detects a
High status. As the normal output voltage of the AC adaptor does exceeds
approximately 16 V, port P67 of the main CPU is normally at Low status.
The main CPU does not process port P67.
Fig. 5.4-9
Film Feed Detector Circuit
Input Voltage Detector Circuit
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