15V Under Voltage Protect - Toshiba 1997 G Series Troubleshooting Manual

9. +/-15V Under Voltage Protect.

The two circuits work independantly, and do not affect
each other.
The +15V turns on transistor Q853. This causes the
collector of Q853 to stay low, about 0V. If the +15V
goes low, Q853 will turn off, and the collector will go
high, to about 5. This will pass through the diode switch,
D 866, and shut down will take place.
The -15V turns on transistor Q854. This causes the col-
lector of Q854 to go to about -15V. If the -15V goes
low, Q854 will turn off, the collector will go towards the
12V supply. Thios will pass through the diode switch,
D867, and shut down will take place.
Figure 21. +/-15V Under Voltage Protect.
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JRS 12-97