Epson LQ-860 Technical Manual page 206

REV.-A
5.3.2 JUNMM Board Unit Repair
If trouble occurs with the JUNMM board, troubleshoot it as described in Table 5-8.
Problem
Symptom
The printer
VX does not
does not
reach 5 VDC.
operate at all.
(The POWER
LED
The RESET
is lit.)
signal is not
canceled.
No mecha-
initialized at
(the printer T h
all
does not
operate at
all).
The printer is No mecha-
initialized,
but enters an
initialized at
error state.
all (the buzzer
rings five
times).
Printing qual- A specific
ity is not
dot is miss-
good.
ing.
Printing is
not execut-
ed.
Table 5-8. JUNMM Board Unit Repair
Cause
The VX gen- Check that transistor Q5 is on.
eration cir-
The reset cir- Check that pin 21 of the IC (8B) is HIGH
The program Check that the IC (6A)
ROM is
defective.
Observe the waveforms at pins 16 (+) and
e
defective.
The carriage Check that phase switching signals are
sent from pins 62, 63, 64, and 1 of the CPU either the IC
does not
move at all.
printer power is turned on (see Figs. 2-58
and 2-59).
The CS drive Check that phase switching signals are
lever does sent from pins 2, 3, 4, and 5 of the CPU
not move up
or down. when the printer power is turned on (see
Figs. 2-66 and 2-67).
The C. G. Check that the IC (3A) and IC (4A) are
inserted correctly.
ROM is
defective.
The IC (2A) Observe the waveforms to check that the
or drive tran- output voltage between the emitter and
sister is collector of the drive transistor for the
specific dot and the corresponding output
defective.
(see Figure 5-8).
The IC (2A) is
defective. head coil drive pulses are sent from HPW
(pin 31) through VSS (pin 9) of the IC (2A).
5-20
Checkpoint
inserted correct-
Solution
ON : Replace
OFF: Replace
Q5 or ZD8.
Replace the
Replace
(6A).
Replace the
or
CR1.
Replace
(lB), IC (1A),
or IC (4B).
Replace the
ing element.
Replace the
(4A).
Replace the
ing defective
element.
Replace the