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7901A
4-59.
When an error condition exists, a R/W Unsafe
signal is developed in assembly A7 and sets the Drive Fault
flip-flop in assembly A 7. This action produces the same
drive fault conditions described in paragraph 4-33. The R/W
unsafe condition also is gated through to the read/write
input logic of assembly A 7 to inhibit a read, write, and
erase function, as well as the head select gates. When the
carriage is retracted and the disc drive enable conditions are
satisfied, an R/W Reset signal is developed in A10 and sent
to assembly A 7 to reset the read/write error detection
circuit. Simultaneously, a low R/W Unsafe output in as-
sembly A10 resets the Drive Fault flip-flop.
4-60.
DISC DRIVE POWER SUPPLY.
4-61.
The disc drive power supply (see figure 5-22),
consists of a line filter, a transformer with two rectifiers
that are chassis mounted, and three regulators that are
located on servo amplifier/regulator assembly A4. A
Theory of Operation
chassis-mounted
terminal
board
in
the
transformer
circuit provides strapping options that enable the disc
drive to be used with various ac sources. A list of
strapping options is contained in section II.
4-62.
During operation, one rectifier-filter network
supplies an unregulated +8 Vdc to assembly A4, and a
second rectifier-filter network supplies a +20 and -20
Vdc to assembly A4. The +8 Vdc is applied to a series
regulator in assembly A4 that provides a regulated +5
Vdc to the disc drive printed-circuit assemblies. The +20
Vdc input to assembly A4 is applied to a series regu-
lator that supplies the regulated +12 Vdc to disc drive
PCA's. An unregulated +20 V dc also is provided by
assembly A4 to assembly A1. The - 20 V dc input is also
passed through a third series regulator that supplies a
regulated -12 Vdc to the disc drive PCA's. Read/write
control assembly A 7 contains circuits that require a
-5-Vdc supply. A zener diode filter network is con-
nected in the regulated -12-V dc supply to provide the
-5 Vdc.
4-9/4-10
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