Intermec EasyCoder 501 XP Service Manual page 111

14.1 Description, cont.
Intermec EasyCoder 501 XP & 601 XP – Service Manual
Booster Converter
The booster converter transforms the AC input voltage to 385 VDC
by sensing the shape of the curve of the input voltage and chopping
it to short pulses, where the pulse amplitude follows the shape of
the curve. The booster is protected by two 3.15A fuses.
Forward Converter
The forward converter transforms 385 VDC to 24 VDC 0.3-5 A
and 42 V 0.1-0.9 A. The 24V is used for the thermal printhead
and the optional cutter unit and the 42V is used for the stepper
motor(s). The potentiometer R89 is used to trim the 24V. Note that
the 24V must be loaded with at least 0.3A before the voltage is
stable enough to allow trimming.
Buck Converter
The buck converter transforms 24 VDC to 5.3 VDC 0.3-3 A which
is used for the logics. The 5.3V can be adjusted by means of the
potentiometer R146.
Fan
The cooling fan at the bottom of the power supply unit is con-
trolled by a thermostat on the primary side cooler and will improve
cooling and spread the heat in the entire machine to avoid local
high temperatures.
Connections
X1 Input voltage >90 to <264 VAC, 45 to 65 Hz
X2 Power to thermal printhead
X3 Power to CPU board
X4 Power to PSU fan
Miscellaneous
The power supply unit is also fi tted with a switch that can shut off
the 24V to the printhead and cutter and a Power Fail Interrupt (PFI)
signal that warns the logics that the power is about to be shut off.
The high voltage and low voltage parts of the PSU is divided by a
thick white line printed on the circuit board.
Troubleshooting
All voltages are available on test points on the CPU board, see
Chapter 15.5. If all voltages are present, but the 24V is too high or
low, load with at least 0.3A and trim on R89.
Jarring sounds or repeated overheating interrupts at high-load print-
ing (for example large black areas) in an otherwise faultless power
supply indicates that the cooling fan may need to be replaced. It is
fi tted at the bottom of the PSU with four plastic screws and con-
nected to X4.
If a fuse is blown, do not try to repair the PSU, but replace the
entire unit!
Chapter 14 Power Supply
109