Digital Equipment RW504-ZA, Руководство по обслуживанию

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6.3 The Power Supply
The power supply is a switching supply that pr5V at 5.6 amperes, +12V
at 0.5 amperes, +12V at 2.7 amperes, and -12V at 0.6 amperes. The supply also
provides the drive power-on reset signal.
The AC line voltage is connected to the power supply through a line cord
receptacle mounted on the power supply PCA. A PCA-mounted power on/off
switch controls both sides of the AC line. The one hot side of the AC line is fused
in the 115 VAC setting. Note that both sides may be hot in the 230 VAC setting.
The fuse rating for both 115 VAC and 230 VAC is 3 amperes (the fuse and fuse
holder cap lengths are different). An input line filter is provided to reduce the
level of AC line transients and the amount of switching noise leaving the supply.
For additional protection, an over-voltage protection device is enabled while in the
115 VAC position in the event that 230 volts in inadvertently connected (a blown
fuse is the only damage that would occur). A diode array and several capacitors
rectify and filter the incoming AC. Included are two thermistors that limit the
initial power-on surge current to approximately 25 amperes peak at both voltage
settings.
The power-on (PVAL-H) reset signal, which is used to control wake-up and
shut-down operations in the drive, is activated by the +5V output. At power-on,
PVAL-H remains high for at least 100 milliseconds after the +5V output reaches
4.75 volts or higher. PVAL-H goes high (shutting the drive down for protection)
500 milliseconds 5V goes below 4.75 volts.
Theory of Operation 6–7