SERVICE MANUAL LC-XB41 - TechEdu.com

Troubleshooting
No Power
This projector provides a function which can be specified a defective area simply by indicating the LEDs. Connect the
AC cord and press the Power button once and then check the LED indication.
- When all of LED indicators are not lighting, the symptom indicates that the primary power supply circuit does
not operate properly. Check the power primary circuit and parts as follow;
AC cord, F601 (Fuse), Power board,
SW902 (Thermal sw.) short in normal
SW902 opens when the surrounding temperature of the switch exceeds 100°C.
- When the WARNING (red) and POWER(red) indicators are flashing, the symptom indicates that the projector
detected an abnormal temperature risen inside the projector. Check the air filters and remove the object near the
intake and exhaust fan openings, and wait until the POWER indicator stops flashing, and then try to turn on the
projector.
The internal temperature is monitored by sensor ICs, IC8811(Lamp), IC8821 (Panel) on the Main board and
IC4831 (Room) on the Temp. board
- When the WARNING indicator lights red, the symptom indicates that the projector detected an abnormality in
the cooling fan operation or in the power supply secondary circuits. Check fan operation and power supply lines,
and the driving signal status.
The P_FAIL signal (Error: L) is sent to pin 215 of IC301 when the abnormality occurres inside the
projector, and then the IC301 sends the shutdown signal, LAMPDC_ON, to the power supply circuit to stop its
operation, and signal BALAST_AC to the lamp ballast board via IC4891 and SW901 to stop
operation of the lamp circuit.
An abnormality occurs on the secondary power supply;
Check power supplies 15.5V, S6V, S-5V. P_FAIL signal becomes “Low” when the abnormality occurs on
any of the power supply lines.
An abnormality occurs on the fan control circuit;
Check FN901, FN902, FN903, FN904, FN905, FN907 and peripheral circuit.
If any of the fans has an error, the fan lock signal drives Q3601 or Q3644 becomes on. As the result, signal
FAN_ERR becomes Low and is sent to lamp ballast board to stop lamp circuit.
An abnormality occurs on the drive signals;
ON_150V signal (Power-on: H) is output from pin 344 of IC301 and switches Q2501,15.5V supply circuit.
ON_5VA signal (Power-on: H) is output from pin 110 of IC301 and switches Q3582, 5VA supply circuit and
switches IC5081, 5V_AUDIO supply circuit. ON_3.3V signal (Power-on: H) is output from pin 11 of IC301
and switches IC5631, 3.3V supply circuit and IC491, 1.2V supply circuit.
LAMPDC_ON signal (Power-on: H) is output from pin 89 of IC301 and supplied to the P.F Control IC,
IC601, on the power supply board through Q681, and PC603.
BALAST_AC signal (Power-on: H) is output from pin 413 of IC301 and applied to pin 2 of IC4891 and output
pin 4 and then supplied to the lamp ballast board through SW901.
CHO_RXD signal at pin 26 of IC301 is applied from the lamp ballast unit. If the abnormality occurred on
the lamp ballast unit, LAMP_DET/CHO_RXD signal becomes “High” and then IC301 shuts down the power
supply circuit.
Lamp Cover switch
Make sure that the lamp cover is mounted correctly. If not
or the lamp cover removed, the lamp does not light on for
the safety. Check the lamp cover and lamp cover switch
(SW901).
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