Acer AL702 AL702 Monitor Service Guide - Page 15

4. Abnormal screen Check the R, G, B video signal from computer input on D-Sub R, G, B connector. OK NG Failure point 1) No R, G and B video signal output from host computer. Check computer 2) Video signal cable disconnection. Check the R, G, B input signals on I301 pin 12, 20, 28, respectively that their level is 0.7Vp-p maximum. Failure point OK NG Is the pulse of the TTL level being output to P303, P304 from the data line of I300? In case of the Red signal. (A Green and Blue signal is the same path, too.) 1) Printed wire broke between D-Sub(R) and I301 pin 12. 2) R341 short. 3) C321 open. 4) R362 open. OK NG Failure point 1) Printed wire broke between I300 data line and P303, P304 2) I317 failure. Check the negative horizontal sync pulse output to P304 pin 38 from I300 pin 80 at TTL level. OK NG Failure point 1) Printed wire broke between I300 pin 80 and P304 pin 38. 2) R351 open A LC502 Check the negative vertical sync pulse output to P304 pin 40 from I300 pin 75 at TTL level. OK NG Failure point 1) Printed wire broke between I300 pin 75 and P304 pin 40. 2) R352 open 3) C416 short Check the positive DE pulse output to P304 pin 42 from I300 pin 74 at TTL level. OK NG Failure point 1) Printed wire broke between I300 pin 74 and P304 pin 42. 2) R355 open 3) C382 short Check the SHFCLK OUTPUT to P304 pin 44 from I300 pin 44 at TTL level. OK NG Process "Checking the resolution change IC movement" section. Failure point 1) Printed wire broke between I306 pin 44 and P307 pin 44. 2) FB314 open 3) FB315 open 4) C380 short 5) C381 short Page 6 Trouble Sh ooting