Printronix p300 Maintenance Manual page 80

2–8. Power Supply (Figure 2–39)
a. P300 and P300XQ
The power supply assembly consists of chassis mounted transformer/rectifier/filter circuits and the power
supply PCBA. AC line voltage is connected to the transformer at primary winding taps selected for the line
voltage in use. A fuse provides circuit protection.
Secondary windings of the transformer provide power to rectifiers, regulators, and filters that generate the
following voltages to the PCBA:
28 V, unfiltered – regulated on the PCBA to provide +28 V to the hammer bank drive circuits and the
paper feed control circuits through fuse F3.
+8 V – applied through fuse F1 to the reference voltage circuit and the logic +5 V supply.
–30 V – applied to the paper feed control circuit through fuse F2.
b. P600 and P600XQ
The power supply assembly consists of chassis mounted transformer/rectifier/filter circuits and the power
supply PCBA. The P600XQ uses the same power supply PCBA assembly as all but the oldest P600 model
printers. The part number of the PCBA for both new machines is 104712–901.
NOTE: Very old P600 machines use a separate circuit card for the motor relay
trigger circuit. This card (P/N 104925–001) is mounted directly above the
shuttle motor, with the solid state relay. These older machines used a different
power supply PCBA (P/N 103250–001) which interconnected with the motor
relay trigger card. PCBA P/N 103250–001 can be replaced by P/N 104712–901
only with the addition of cable assembly 105392. The best course of action is to
send the old cards to Printronix for repair, or to replace the entire power supply
assembly (P/N 105513–901).
The AC line voltage passes through one or both sides of a dual circuit breaker and appears at the trans-
former primary winding taps selected for the line voltage. The circuit breaker trips magnetically when
excess voltage is detected in the +36 Vdc on the power supply PCBA. There is also a thermal trip feature
that detects excessive T1 primary current.
Secondary windings of the transformer provide reduced AC voltage to bridge rectifiers and filters that
provide the following voltage to the PCBA:
36 Vac – used to produce unfiltered +36 Vdc for the hammer bank and +70 Vdc for the paper feed drive
circuits.
+9.5 Vdc – applied to the reference voltage circuit, the +5 Vdc supply for the logic PCBAs and to the
+9.5 V fault circuit.
–36 Vdc – input to the –12 Vdc voltage regulator on each of the printer's PCBAs, and to the –36 V fault
circuit.
The power supply PCBA contains several DC voltage supplies used throughout the printer. Additionally,
fault detection circuits monitor the supplies and the paper out switch. A paper feed disable circuit controls
the action of the paper feed drive circuit. Finally, the motor relay trigger circuit provides temporary AC
voltage to the shuttle motor start winding to start the motor turning. This circuit removes power from the
start winding when it detects the shuttle is up to speed.
2–58 P300/P600 Principles of Operation