LL-T1820 (serv.man5). Troubleshooting - Sharp Monitor Service Manual (repair manual). Page 2

PC-UM10M

LL-T1820-H/B   TROUBLE SHOOTING

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The port from which the analog signal cable 
was removed is the input signal port selected?

48th pin and 49th pins of IC601 are in H level 
(DC+3.3V)?

LD618 and LD621 are in H level (about 
DC+1.9V)?

LD801 is less than DC+1.0V at maximum 
brightness?

1st pin of CN2, CN3, CN4, CN5, CN6, and CN7 
on inverter PWB unit is about 750 Vrms?  (Use 
caution not to get electric shock accident. Use 
a high-voltage probe (more than 100:1) for 
measuring voltage.)

Check analog signal cable and CN100 
(CN200).

Check SDA and SCL signals and circuits 
around IC401 and IC601.

Press INPUT key to switch over to the 
correct input signal port.

Check the power unit and cable and their 
connections, and DC+12V power supply 
line.

Check BL_EN signal and circuits around 
CN801.

Check BRT_VR signal and circuits around 
IC603.

Signal waveforms of test terminals LD303, 
LD304 (LD310, LD311) are normal?

Signal waveforms of test terminals LD305, 
LD306 (LD312., LD313) are normal?

Signal waveforms of 31st and 32nd pins of 
IC401 are normal?

Check SW PWB and SW cable and their 
connections.

48th pin of IC601 is in H level (DC+3.3V)?

continued from  1

LD618 is H in level (about DC+1.9V)?

Check SW PWB and SW cable connections.

Test terminal LD804 is DC+12V?

LD800 is in H level (DC+5V)?

Check lamp inside LCD module.

Check circuits around IC601.

Check Q600 and its surrounding circuits.

Replace inverter PWB unit with a new one.

Check circuits around IC601.

Check Q600 and its surrounding circuit.

Check circuits around IC300 and IC301.

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