Epson 2070 Service Manual - Page 134

Table 5-6. Repairing the C166 PSB/PSE Board Assembly Continued, Cause, Checkpoint, Solution

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Troubleshooting LQ-2070 Service Manual Table 5-6. Repairing the C166 PSB/PSE Board Assembly (Continued) Problem The 35 V and 5 V lines are not output when the printer is powered on. ^ Cause Q32 is dead. Q31 is dead. Checkpoint Check that the resistance between the collector and emitter is infinite. Solution Replace the Q32. Check that the resistance between the source and drain is infinite. Check the voltage waveform at pin 8 of IC51. The voltage waveform is as follows: Replace the Q31. Replace IC51. The +5 V line is not output. IC51 is dead. Q51 is dead. Check the voltage at pin 12 of IC51. Check the voltage waveform between emitter and collector of Q51. Replace Q51. ^ ^ The PWDN signal is constantly HIGH. L51 is short. IC52 is dead. Check the resistance between both terminals of L51 Check whether the voltage of pin 6 is more than 1.3 V or not. If the voltage is more than 1.3 V, IC52 is dead. Replace L51. Replace IC52. 5-12 Rev. A

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Table 5-6. Repairing the C166 PSB/PSE Board Assembly (Continued)
Problem
Cause
Checkpoint
Solution
The 35 V and
5 V lines are
not output
when the
printer is
powered on.
Q32 is dead.
Check that the resistance between the
collector and emitter is infinite.
Replace
the Q32.
^
Q31 is dead.
Check that the resistance between the
source and drain is infinite.
Replace
the Q31.
The +5 V line
is not output.
IC51 is dead.
Check the voltage waveform at pin 8 of
IC51. The voltage waveform is as follows:
Check the voltage at pin 12 of IC51.
Replace
IC51.
^
Q51 is dead.
Check the voltage waveform between
emitter and collector of Q51.
Replace
Q51.
^
L51 is short.
Check the resistance between both
terminals of L51
Replace
L51.
The PWDN
signal is
constantly
HIGH.
IC52 is dead.
Check whether the voltage of pin 6 is
more than 1.3 V or not. If the voltage is
more than 1.3 V, IC52 is dead.
Replace
IC52.
Troubleshooting
LQ-2070 Service Manual
5-12
Rev. A