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2031 LP CIRCUIT THEORY

[Power up/down write protection circuit schematic]

Power Up/Down Write Protection

This circuit prevents erroneous data from being written on the disk during power up/down sequences. During a power up, the 12VDC supply is not applied to the R/W coils and amplifier circuits before the processor has control of the logic. During a power down, the 12VDC supply is removed from the R/W coils and amplifier circuits before the processor loses control of the logic.

Q1 acts as a series pass transistor biased to regulate the 12VF output to the R/W coils and amplifier circuits. Q2 is a feedback amplifier monitoring the 5VDC supply. CR5 develops a precise reference voltage for Q2. L7 and C12 delay the 12VDC supply.

[Write protect switch schematic]

Write Protect Switch

Connector P6 connects the control circuits to the W/P switch and activity light. UCD4, a 6522 VIA, monitors the state of the write protect sensor on pin 14 and controls the red activity LED on pin 13.


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This page has been created by Sami Rautiainen.
Read the small print. Last updated December 08, 1998.