Epson Stylus COLOR 900 Service Manual page 80

EPSON Stylus COLOR 900/900N
Table 3-18.
Isolating the Problem on the Power Supply Board (continued)
Step Problem
7 Is the main switching Check the electrical continuity of the switching
FET (Q1) defective? FET by trying the four patterns below. Be sure to
pay attention to the polarity. If the main switching
FET is good, the results should be as shown under
the figure.
Step 1: Off, Step 2: On, Step 3: Off, Step 4: Off
8 Is an NPN transistor Check the electrical continuity of Q2 and Q54 on
defective? the C265 PSB/PSE board using the four patterns
below. Be sure to pay attention to the polarity. If
the transistor is good, the results should be as
shown under the figure.
Step 1: On, Step 2: Off, Step 3: Off, Step 4: On
Solution
Table 3-19.
Isolating the Problem on the Power Supply Board (continued)
Step Problem
9 Is a PNP transistor Check the electrical continuity of Q3 and Q53 on
defective? the C265 PSB/PSE board using the four patterns
below. Be sure to pay attention to the polarity. If
the transistor is good, the results should be as
shown under the figure.
Step 1: Off, Step 2: On, Step 3: Off, Step 4: On
10 Is the +5 V regulator Using an oscilloscope, check the output waveform
(IC51) defective? at Pin 5 of IC51. The output waveform should be
as shown below.
Chapter 3 Troubleshooting
Solution
I C 5 1
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