Drive Reset Circuit Explanation - Panasonic TH-42PX80U Service Manual

Drive Reset Circuit Explanation

The DRV RST circuit of the D board is used to monitor the physical connection of the D board to the C
board. DRV RST input to IC9500 and IC9003 must be high for the unit to operate. The D board
provides the 5V source needed to power the C boards. On the C1 board and the C2 board, the 5V is
routed back to the D board via connector C11/D31, C21/D33 to activate the 5V SENSE circuit. A
voltage divider consisting of R9157 and R9162 (For TH-42PZ85U) develops a voltage drop that causes
the collector of transistors Q9058, Q9059, and Q9060 to become low. As a result, the base voltage of
Q9061 also becomes low causing its collector to go high. The output voltage is applied to IC9500 and
IC9003 as DVR RST.
When the 5V SENSE circuit does not detect 5V from the C1 board and the C2 board, the DVR RST
output becomes low. The unit goes into shutdown and the power LED blinks 6 times.
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