A1286 820-2915b chime ok, but no image no bklight

[marce002]

Hello

I have this a1286 with minor water damage, after cleaned ISL area turns on and chimes , load os but: no image no backlight.... LCD_PWR_EN is 0vol ..
I have done gmux bypass to many a1286s with gpu issues, so though this would be the case. routed jumpers to avoid the gpu and removed resistor r8911 as usual to disable ati gpu... but still no LCD_PWR_EN signal...

what can be going on to not have LCD_PWR_EN enabled? i do have 3.3v in pin 4 at lcd connector but not pins 2,3, because u9000 is not enabled by this missing LCD_PWR_EN

thanks in advance

pd i did not remove gmuch chi only bypassed in site like this img:

[mon2]

Re: A1286 820-2915b chime ok, but no image no bklight

What is the voltage of R9678, pin # 1 ?

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

Hi mon it is 8.2mV at #1 and 2.66V at #2.. resistor is in range

[mon2]

Re: A1286 820-2915b chime ok, but no image no bklight

Check the resistance to ground of LCD_PWR_EN pin. Any liquid damage in this area ? Trace is ok from source (U9600) to target ?

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

it is 8.2kohm and traces are ok there around...

remember that i have a mod jumper from #1 of r9678 (lcd_pwr_en) to R2015 pin 1 (lvds_ig_panel_pwr)

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

R2015 is the source for my lcd_pwr_en after my mod.... is it? .. which in fact should be 100kohm and i have it at around 8kohm... mmm

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

bad pch?

[mon2]

Re: A1286 820-2915b chime ok, but no image no bklight

But you don't have an image?

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

nop no image no backlight but do have brain ...replaced that resistor and after soldered in it is 8kohm so in circuit resistor parallel afects messurement.

[mon2]

Re: A1286 820-2915b chime ok, but no image no bklight

Do you get external video?

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

please understand me.. i ve just made a bypass in order to fix gpu issues and that excludes external monitor usage

[marce002]

Re: A1286 820-2915b chime ok, but no image no bklight

fixed it was bad corrupted efi bios so if you have chime but lcd pwr on signal not enabled might NOT be a bad pch or bad connector screen or coils around... thks mon

[mon2]

Re: A1286 820-2915b chime ok, but no image no bklight

Well done! Thanks for the update.

[gurangax]

Re: A1286 820-2915b chime ok, but no image no bklight

fixed it was bad corrupted efi bios so if you have chime but lcd pwr on signal not enabled might NOT be a bad pch or bad connector screen or coils around... thks mon

Thanks for tips. I managed to fix mine same problem. flashed with other firmware and it worked.