Service manual

Avantra 36/44 Service Manual
2-14 Functional Analysis
2.9 Power Supply
The power supply is a low voltage switching supply, with non-adjustable outputs.
A switch mounted to the side of the power supply configures the input voltages of
110 or 220 volts. The 300 watt power supply generates the following voltages:
+ 5.0 volts 20.0 amps
+24.0 volts 8.0 amps
+12.0 volts 1.0 amp
-12.0 volts 1.5 amps
2.9.1 Additional Voltages
Two other voltages necessary to the system are generated locally with converters
on the DEC PCB:
- 5.2 V
9.0 V
The -5.2 volts derives from -12.0 volts, which is used for the ECL logic on the DEC.
The +9.0 volts derives from the +12.0 volts and is used to supply power to the diag-
nostic modem.
2.9.2 Power Distribution
A discrete wiring harness provides power from the power supply to the DEC PCB.
The signal cabling supplies power for isolated boards within the system. This har-
ness will be included with the power supply as a complete field replaceable unit.
2.9.3 Power Good
The power supply generates a “power good” signal, which is used as a reset within
the system. This signal goes “true” when all supplies are within regulation specifi-
cation. The signal goes “false” at least 2 ms. prior to any of the supplies going out
of regulation. This gives the DEC and OCP enough time to save any non-volatile
parameters that may have changed since the last power-up cycle.
CAUTION:
An internal fuse is located in the power supply, but it is
not necessary to check or replace it. If the fuse should burn out,
consider the power supply as the cause.