Newhaven IPS LCD Backlight Issue

[InsertUsernameHere]

Hi guys,

I have a few of these LCD's (NHD-7.0-HDMI-HR-RSXP-CTU) out in prototype systems and we have started having back light failures (2 in one week).
I'm not 100% sure on the best way to try and trouble shoot this one as everything seems to be ok.

The weird thing is that when I put my multimeter across D4 (in voltage mode) the backlight magically seems to come back to life, D4 seems to test ok as well.
I'm not too sure if its something to do with the driver chip maybe?



Any ideas how to test and trouble shoot this one?

Cheers guys.

[coromonadalix]

Is the control  line properly driven    it a high pull up,  parts around the chip  okay, well soldered, are they properly rated and having good values as given in the reference design ?? (havent seen the datasheet)

Clean input voltage ?,   is the backlight circuit on the good display is under 200 ma ?

If you say your circuit work for a short time,  is the driver Ic  overheat ??

Good connectors contacts,   I had a similar problem with our 7" Sharp displays, it was based on 3x led group on a 24vdc backlight system, when we moved the backlight fpc connector, we could see some leds (group) turned off, it gave a strange effect on the screen bottom

EDIT
OH  ok  i see the display specs and photos,  it has eveything on its back,  hdmi interface, supply input, drivers ic's  etc ...    nice one

Is your supply range is between 5 to 7 vdc at 1.3 amps ??

Do you use the external pwn connector ??

[InsertUsernameHere]

Yeah the Power Supply is good, I also have tested with my bench power supply.
I dont use the PWM so the display is just always on 100% brightness.

The displays have been working for over 12 months now out in the field so I dont think its an overheating issue.

Everything looks to be ok.

[coromonadalix]

maybe drop the intensity by 5 - 10% by the pwm input could make it last longer ?  since it wont be at 100% all time.