820-3437 No image/bklt - missing EDP_BKLT_EN to Q7707

[george-a]

Hi ladies and gentlemen - its the macbook air week! Welcome to our show!


This one turns on but no image (thus no backlight) - it powers on, green/orange light ok, CPU gets hot.

PPHV_S0SW_LCDBKLT is 0V (no shorts to ground in the vicinity) and so is signal EDP_BKLT_EN to Q7707 (this comes from CPU). I measure L8550 VLDO and VDDIO to be ok at 5V and 3.3V respectively.

Have no spare LCD to try - I do but it belongs to another customer and I dare not damage it.


So since there is no image and I have no other LCD what could I do to go further? (Unless testing another LCD is generally risk-free).

Any way to test if LCD is detected to rule that out?


duke, I will waste some of your time after all


george

 

[dukefawks]

USB mouse lighting up? Chimes?

 

[george-a]

no chime, no mouse light.. I have the motherboard lying on the bench - the mouse should still light up right? IO board & flex connected of course.

 

[dukefawks]

So it is brain dead. Was this a liquid spill? Voltage on L7310?

 

[george-a]

Happy New Year to you and everyone.

Brain dead means?

1.74V at L7310.

 

[dukefawks]

All power is ok but it does not boot. What is the history?

 

[george-a]

It was not LD - I didn't confirm that earlier - but I would have mentioned it - and the owner is a student (girl) who says it just stopped working. Using original magsafe.

should we look towards EFI or the CPU itself?

 

[dukefawks]

This could really be anything. I would inspect the board closely for damage and then the first thing to try is the ROM. Backup the old! Besides that I don't think there is much you can do in these cases.