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2850 Flex board no backlight

G.Beard

G.Beard

New member
Hi.

Had this board on a shelf for a long time. I think I may have fixed PPBUS at some point.. Don't remember, it's mine.
Anyway, backlight is working but flex the board and the backlight goes off. I have tried replacing the backlight circuit, running wires all over the shop, poking the board in various places to find the spot, tried pissing about poking the GPU MUX which does turn backlight on and off but no more so than poking around the GPU reg or poking the 6259 or the USB HUB U3700. Fucking board's been poked more times than Louise Fokken. Tried a new LVDS connector and different screen right at the start too. Just can't locate it.

Bad via?
Bad ceramic cap?
Bad solder joint?

Guess it could be all or any, but if there is a common cause for this, please let me know.
 
2informaticos

2informaticos

Administrator
Staff member
Always has image, only backlight goes off?
Post BKLT_EN, LVDS_BKL_PWM_RC, LCD_BKLT_EN and SMC_LID for no backlight case.
 
G.Beard

G.Beard

New member
2informaticos said:
Always has image, only backlight goes off?
Post BKLT_EN, LVDS_BKL_PWM_RC, LCD_BKLT_EN and SMC_LID for no backlight case.
Click to expand...

Actually, if I flex the board in different ways sometimes it turns off backlight and sometimes the image too.


dukefawks said:
U9600 MUX problem. Very thoroughly remove the edge bonding and reflow MUX.
Click to expand...
I'll try that today.


2informaticos said:
Post BKLT_EN, LVDS_BKL_PWM_RC, LCD_BKLT_EN and SMC_LID for no backlight case.
Click to expand...

I've not tested it. I'll flow the mux first.
 
G.Beard

G.Beard

New member
I fucked it up and knocked the fucking chip. What's the pin pitch / ball size for these chips? Need to reball it :(
 
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