Epson Stylus Color 980 Service Manual page 93

EPSON Stylus Color 980
Table 3-19.
Isolating the Faulty Part on the Power Supply Board (continued)
Step Check Point
9 Is the main switching Check the electrical continuity of the switching
FET (Q1) defective? FET by trying four patterns below. Be sure to pay
attention to the polarity. If the main switching FET
is good, the findings should be as shown under the
figure.
Step 1: Off, Step 2: On, Step 3: Off, Step 4: Off
10 Is the NPN connection Check the electrical continuity of the NPN
transistor defective? connection transistor on the C265 PSB/SE board
by trying four patterns below. Be sure to pay
attention to the polarity. If the NPN contact
transistor is good, the findings should be as shown
under the figure. Note the NPN connection
transistor is shown in the circuit diagram as
described below.
Step 1: On, Step 2: Off, Step 3: Off, Step 4: On
Troubleshooting
Action
Overview
Table 3-20.
Isolating the Faulty Part on the Power Supply Board (continued)
Step Check Point
11 Is the PNP connection Check the PNP connection transistor on the C265
transistor defective? PSB/SE board in the same manner described in
the previous step.
Step 1: Off, Step 2: On, Step 3: Off, Step 4: On
12 Is the +5 V regulator Check the IC51 for the oscillation waveform
(IC51) defective? (measured by using a oscillo scope) output from
the Pin 5. If the output waveform is as shown
below, it means the IC51 is working properly.
Revision A
Action
89