Casio PR-420A User Manual

— 5 —
Trouble Cause Checkpoint Note
1) Does not work
at all.
2) No display.
3) No print.
4) Poor display.
5) Poor printing
• Motor does
not stop.
• Missing of
digits.
• Refer to the printer service manual published separately.
VDD, VSS, VM, VF1, and
VF2 are OK?
Check the pulse signals
from LSI.
If VF1, VF2, Digit and
Segment signals are OK.
VM=17V (while printing)
Check detector of printer
block and timing signal.
Secondary voltage
of transformer
Waveforms of each
pin
VF1, VF2
Signal D1 ~
S1 ~
Between LSI and
display tube
5. TROUBLESHOOTING
• Defective power transformer
• Defective LSI
• No voltage at VF1, VF2
• No digit signal or no segment
signal
• Defective display tube
• Poor voltage VM
• Defective motor
• Defective LSI
• Short or open circuits between
digit signals and segment sig-
nals.
• Defective display tube
• Timing signal is bad.
• Defective printer magnet

Casio PR-420A Specifications

General

Brand	Casio
Model	PR-420A
Category	Calculator
Language	English