Epson LQ-2550 Technical Manual page 231

Symptom
dead.
+35 V line.
lo%)
NOTE: The parenthesized component numbers indicate those for the ROPSE board.
Table 5-7. ROPS/ROPSE Board Unit ReDair
Cause
The FET (Q3 (Q4)) does
not turn on.
Checkpoint
. ObseNe the voltage between pins
12 and 7 of IC2. (Approx. 10.6 V)
. Measure the resistance across
(RI 4). (Approx. 20.0 ohms)
. Measure the resistance across
R1O (Rl 3). Approx. 20.0 ohms)
. Observe the voltage wave-form
between the gate and source of
. Observe the voltage waveform be-
tween the drain and souce of Q3
. Measure the voltage between pins
4 and 7 of IC2. (Approx. 1.6 V)
. Measure the voltage between pins
12
and 7 of IC2. (Approx. 10.6 V)
. Observe the voltage waveform be-
tween pins 5 and 7 of IC2. See
Figure 5-13.
Observe the voltage waveform be-
tween pins 11 and 10 (pins 8 and
9) of IC2. See Figure 5-13.
. Measure the voltage between pins
14 and 13 of IC2. (Approx. 5.0 V)
5-19
Solution
Replace IC2.
Replace RI 1 (RI 4).
Replace Q1O (R13).
Replace Q3 (Q4).
Replace IC2.