Epson MX-80 Technical Manual page 55

The carriage assembly moves properly, but none of the 9 dot wires operates to print a dot.
No.
Cause of Trouble
Faulty head driving pulse
width, or no head driving
pulse is output
No drive signal is input to
the head driver
Check Point
• Check the terminal TO on the driver cir
cuit board with an oscilloscope, for
proper voltage and pulse width.
Appro*. 400 /AS
• Check the base of each of the 9 head
driving transistors (Ql—Q9) for proper
input voltage
Appro*. IV
400 fjLS
Repair Method
• If the pulse width is abnor
mally short (less than 200 /as).
adjust VR1 so that the pulse
width becomes 400 /Asec at
24 VDC. See paragraph 4.3.1.
(Refer to Fig. 5.4 for the loca
tion of VRI.)
•If no pulse is output, the con
trol circuit board is defective.
See paragraph 3.4.3.
•If no signal is input, control cir
cuit board is defective. See
paragraph 3.4.3.
SYMPTOM 4 . . . . . .
The carriage assembly moves properly, but some of the dot wires do not operate to print dots.
No.
Cause of Trouble
Check Point
Repair Method
1
Defective print head unit
• Check the driving transistor (Q1~Q9)
of each dot wire that does not operate,
for proper driving voltage waveform.
• If the waveform is normal, the
print head unit is defective.
Replace it with a new one. See
paragraph 3.3.3 (2) for re
placement.
1
Appro*. 24V
Appro*. 45V
400 /AS
2
Defective driver circuit
• If the waveform is abnormal in the
above.check. check the driving transis
tor of each dot wire that does not oper
ate. for proper base voltage.
• It no collector voltage is output in the
above two checks, check the Pin No 13
of CN6 for output of -F24V (in normal
character print mode).
• If the base voltage is properly
input, the driver circuit board
IS defective. Replace it with a
new one. See paragraph 3.3.2
(1) for replacement.
•If -I-24V is not output, the
driver circuit board is defec
tive. Replace it with a new one.
See paragraph 3.3.2 (1) for
replacement.
Appro*. IV
Appro*. 400 /AS
3-17
REV. A