HP WF1907 Service Manual page 18

4.5 Abnormal OSD display adjust problem
Check the input level whether was changed when pressed
function keys on the P308 pin 2, 3, 4, 5. (normal is 3.3V,
when push button, generated different voltage. pin 2, 4 is
Check the input voltage level whether was changed when
pressed function keys on the I306 pin 114, 115. (normal is
3.3V, when push button, generated 2.46V or 2V.)
Failure Point
I306 is failure.
2.46V, pin 3, 5 is 2V)
NG
OK
NG
OK
Failure Point
1) Function key wire disconnection.
2) Function key wire is failure.
3) Function key board is failure.
Failure Point
1) Printed wire broke between P308 pin 2 and I306 pin 115.
2) Printed wire broke between P308 pin 3 and I306 pin 115.
3) Printed wire broke between P308 pin 4 and I306 pin 114.
4) Printed wire broke between P306 pin 5 and I306 pin 114.
5) C381, C382, R367, R368, C387, C388, C389, C390, C391, C392
is short.
6) R378, R379, R381, R382, R384, R385 is short or open.
7) R380, R383 is open.
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