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1541 circuit theory

[wRITE AMPLIFIER 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. l8 AND c15 DELAY THE 12vdc SUPPLY.

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tHIS PAGE HAS BEEN CREATED BY sAMI rAUTIAINEN.
lAST UPDATED aPRIL 18, 1998.
rEAD THE SMALL PRINT.