QM7500 Technical Manual
QM31930/03093 Rev AD
Troubleshooting 3
Troubleshooting
Problem
Possible Cause
Solution
Row of keys fail to work.
Chips loose on the circuit board.
Make sure the RAM chip (U8) and
the software (U7) are properly
installed, and that the Zilog chip is
not loose.
Printed circuit board is defective.
Replace the printed circuit board.
(See page 19.)
The green light is on, but the unit
will not print.
Wires loose from the barrel
terminals.
Reseat any loose wires in the
barrel terminals. (See Figure A.)
The unit prints intermittently.
Wires disconnected from the
barrel terminals.
Reseat any loose wires in the
barrel terminals. (See Figure A.)
The print light is constantly
orange.
Printhead photocell board
defective.
Replace the printhead photocell
board. (See page 15.)
The machine resets itself.
Valve shorted out.
Replace the defective valve. (See
page 12.)
The unit will purge but not print.
Wires loose from the barrel
terminals.
Reseat any loose wires in the
barrel terminals. (See Figure A.)
A dot or dots missing.
Unit ran out of ink.
Replace the ink bottle.
Nozzle clogged.
1. Spray the nozzle block with
solvent.
2. Backflush the nozzle. (See
page 10.)
3. Replace nozzle block. (See
page 11.)
Tube and jewel assembly in the
nozzle block cracked,
Replace the nozzle block. (See
page 11.)
Worn valve.
Increase dot size to temporarily
adjust for worn valve.
Valve became loose from the
valve board.
Reseat the valve on the valve
board.
Valve is defective.
Replace the valve. (See page 12.)
Ink line became loose.
Reattach the ink line.
Wires loose from the barrel
terminals.
Reseat the wires in the barrel
terminals. (See Figure A.)
