Power Supply; Ac Power; Dc Power - Printronix

P9212 Maintenance Manual

Power Supply

The power supply board, ac input connector, power switch/circuit breaker,
and a cooling fan are contained in a removable steel module at the rear of the
printer. The power supply senses and adjusts to any commercial electrical
system that provides ac mains potential in 50 or 60 Hertz systems. AC input
power is converted to +48 volt and +12.5 volt dc power and sent to the
hammer driver board for filtering. The hammer driver board passes the
filtered +48 and +12.5 Vdc to the mechanism driver board for distribution to
logic and electromechanical circuits. The power supply board supplies +5
Vdc power directly to the mechanism driver board or to the backplane in
printers using the LMI print engine.

AC Power

The power supply operates on ac voltages ranging from 88 to 135 or
176 to 270 volts. It can tolerate variations in frequency of 47 to 63 Hz. The
power supply is designed to withstand an ac input overvoltage of 125% of
nominal for one second with no degradation of dc output voltage or damage
to printer circuits.

DC Power

The power supply board contains two dc power supply systems for the
printer. The first is a + 5 volt bus for logic circuits. The second consists of
+ 48 volt and + 12.5 volt buses for the electromechanical sections of the
printer (all drive motors and the hammer bank).
The + 5 volt and + 48/12.5 volt supplies have separate return lines. Both
returns are tied together in a single–point ground at the mechanism driver
board.
There is an opto–isolated logic level input from the printer that can shut
down and latch off the + 48 volt and + 12.5 volt supplies while maintaining
the + 5 volt output. The return for this signal is the + 5 volt return. In
addition, this shutdown circuit discharges and latches the + 48 volt down to a
level lower than 15 volts in less than 300 milliseconds and requires recycling
of the power switch/circuit breaker to reset the latch.
The + 5 volt power supply has its own inverter, separate from the + 48 volt
and + 12.5 volt outputs to provide logic power if the +48/12.5 volt supply is
shut down.
2–38 Principles of Operation