Epson LQ-2550 Technical Manual page 230

REV.-A
Symptom
NOTE: The parenthesized component numbers indicate those for the ROPSE board.
Table 5-7.
Cause
Transistor Cll does not
Triac TY 1 is defective.
OP. AMP.
defective.
Fuse resistor RI 9 (R21)
is open.
Fuse resistor R22 (R25)
open.
is
Shunt regulator Q4 (Q5)
is defective.
Photo coupler PC 1 is
defective.
Zener diode ZD 1 is
defective.
Checkpoint
Observe the voltage wave-form
between the base of Q 1 and pin
6 of T1. See Figure 5-9.
. Observe the voltage waveform be-
6 of T1. See Figure 5-10.
.
Check the continuity between T1
and T2 of TY 1. See Figure 5-11.
Check the voltage between pins 8
and 2 of IC 1. (Approx. 10.6 V)
. Check the voltage between pins 4
and 2 of IC 1. (Approx. 10.7 V)
. Check the voltage between pins 1
and 2 of ICI. (Approx. 7.4 V)
. Measure the resistance across
. Measure the resistance across
. Measure the voltage between the
cathode and anode of Q4 (Q5).
. Measure the voltage between the
gate and anode of Q4 (Q5).
Measure the voltage between pins
1 and 2 of the photo diode in
Confirm the voltage between the
anode and cathode of ZD 1.
5-18
Solution
Observe the output
voltage waveform of
Q2.
Replace
Replace Q1.
Replace
TY1.
Replace IC 1
Measure the voltage
between A and K of
Replace R19 (R21).
Replace R22 (R25).
Replace Q4 (Q5).
Replace PC 1.
Replace ZD1.