LCD Not Working?

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cheesemonkeys
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LCD Not Working?

Post by cheesemonkeys » Sun Dec 29, 2019 12:30 am

Not sure if I'm doing something wrong with the settings. I have the #tester mode on the settings, nothing else I have changed on the SD card. With the 320x240 screen, everything works as expected and the diagnostic program loops fine. With the 640x480 screen, there is no backlight, and inductor whining. All the LEDS I believe show normal status.

Is there a setting I need to change? I read the wiki and it said nothing to change with 1.3D
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kite
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Re: LCD Not Working?

Post by kite » Mon Dec 30, 2019 9:38 am

Hi, if you remove the CM3 and power on, under where the CM3 was should be an LED saying "BL_OK", is that on? Is that area of the board REALLY hot? (be very careful finding this out, if the BL chip has gone bad then it possibly may burn you (it thermally limits itself but in the 105*C region!). I'm suspecting it is like this, in which case send me an email and I'll sort out repair/replacement for free

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Re: LCD Not Working?

Post by cheesemonkeys » Wed Jan 01, 2020 2:02 pm

Thanks for the quick reply Kite. I don't see a LED labeled BL OK but one just BL and its lit red. (see attached). I let it whine for 60 seconds but dont particular notice anything under the CM3 area that is warm or hot.
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kite
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Re: LCD Not Working?

Post by kite » Mon Jan 06, 2020 8:52 am

Ah yep it's called "BL" :)

Do you have a multimeter/voltmeter? Could you do it exactly as you have done, and put the red probe on the highlighted pads, and the black probe on any GND (e.g. the metal of the SD card reader or the USB C connector, or a pad labelled "GND") and let me know the voltage. The expectation is that it is about 26-42v in that range. Can you do it WITHOUT the screen, and then WITH the screen?
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cheesemonkeys
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Re: LCD Not Working?

Post by cheesemonkeys » Mon Jan 06, 2020 9:27 pm

I got 44v at both locations in both conditions:

without screen
c59 44v
c17 44v

with screen
c59 44v
c17 44v

Edit: not sure if you circled diode 3 but it is also 44v both w + w/o screen

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kite
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Re: LCD Not Working?

Post by kite » Tue Jan 07, 2020 6:23 am

Yeah all are the same signal, and that all sounds perfect! Right, i'm 99% sure then that the LCD you have is at fault. The backlight IC and circuit is working correctly, but it's like the LEDs are dead in the screen!

As a last thing, can you inspect the LCD connector on the board, check there is no debris or anything, and that the LCD contacts are clean? If no joy there, send me an email and i'll send you a replacement LCD right away :) ideally if you could let me know today/tonight i can send it tomorrow

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Re: LCD Not Working?

Post by cheesemonkeys » Tue Jan 21, 2020 12:26 pm

Just wanted to let everyone know Kite is great. We determined it to be a bad 640x480 lcd and he sent a new one and it works like a charm. A+

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