Specifications

2.5.4 Shuttle Power Supply Regulator (SPSR)
The SPSR board is located in the power module on the left side of the
printer. It provides the four regulated dc voltages needed by the printer:
5.10 V, 12 V, -12 V, and 42 V.
Visual LED indicators on the board are used to indicate the presence of
the voltages.
The SPSR board provides crowbar protection for the 5.10 V circuit.
A current limiting circuit is provided to protect the power switching
transistor.
Since the SPSR has a high current usage, it has forced air cooling.
An internal crowbar circuit across the 5.10 V output activates at 6.5 V
and reduces the output to at least 2.5 V ac input power must be removed
for at least 30 seconds before the circuit resets and normal operation is
possible.
The SPSR disables all voltages if the 5.10 V bus cannot attain full voltage.
All outputs can withstand a short for at least one minute.
The SPSR needs forced air cooling.
2.5.5 Shuttle Power Supply Discharge (SPSD)
The SPSD board is located in the lower rear enclosure of the printer.
Its purpose is to discharge the 85V bus voltage maintained by the 85 V
holdup capacitor, and hence the 42V bus voltage derived from it, to less
than 18 V in one second. This occurs only when the shuttle access door
in the top enclosure is opened, operating an interlock switch.
THEORY OF OPERATION 2–15