Over Current Protect - Toshiba 1997 G Series Troubleshooting Manual

5. +30 V Over Current Protect.
Resistor R 7782 is the Sensing Resistor. It is a very
small value. It can cause intermittent shut down prob-
lems.
The current flow to the convergence circuits flow through
this resistor. Too much current will cause an increase in
the voltage across the resistor. Transistor Q768 is bi-
ased just below cutoff. A slight increase in voltage across
6. +15V Over Current Protect.
The +15V over current protect operates in a similar fash-
ion as the +30V over current protect.
R 7782 will turn on Q768. The collector then goes to
about 30V. This is the monitor point for shut down.
The normal collector voltage is Zero.
This trigger voltage will turn on Q758. It's collector
will go low, to about 0V. This, in turn, causes transistor
Q757 to turn off. Q757's collector rises to about 5V,
causing shut down to occur.
Figure 17. +30V Over Current Protect.
Figure 18. +15V Over Current Protect.
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JRS 12-97