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820-00165 - MacBook Air No Display

M

mccafe

Member
We have an 820-00165 that customer said was flickering all of a sudden and then it just went black. He said he didn?t drop, didn?t spill anything on it. No faint display when flashing a light over it. No signs of corrosion - completely clean. Tested a known working board and the display assembly is working.

What is the next step to troubleshooting this?

Thanks!

EDIT: I forgot to mention that the MacBook turns on. Chimes, etc.
 
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2informaticos

2informaticos

Administrator
Staff member
Do you get 3V at pins 18/19 of J8300?
Check it when machine chimes; should appear at least 1-2s.
If not, check L8304.
 
M

mccafe

Member
3.3 volts at pins 18/19 of J8300 for a few seconds when machine chimes, yes. Connector looks good, continuity on all pins. l2c sda/scl lines check out too.

DP_INT_HPD 0 volts
 
M

mccafe

Member
Unfortunately, yes I did check with LCD connected. I wish it was that easy lol

And yes, 3v split second then 0v.
 
2informaticos

2informaticos

Administrator
Staff member
If you detect pulse at DP_INT_HPD, then check al data lines; voltage and diode mode to ground.
Also check the four C832x capacitors and R836x, as all pull-down resistors too.
 
M

mccafe

Member
Okay,

With LCD (pulse lasts a split second)
R8318 & R8317 OL (or super high resistance) 0.13v to 0v pulse
R8380 & R8370 OL 1v to 0v pulse
R8361 - 0.5 diode - 3v to 0v pulse
R8362 - 0.5 diode - 3v to 0v pulse
R8360 - 0.55 - 3v -> 0 pulse

Without LCD (pulse lasts 2-3 seconds as compared to with LCD)
R8361 - 0.7 - 3.3 -> 0v pulse
R8362 - 0.7 - 3.3 -> 0v pulse
R8360 - 0.7 - 0v

Caps all have 0.25 on diode pin 1 and OL pin 2
All traces from pin 2 of all 4 caps to connector checks out fine

Connector looks pristine condition. Could there be an issue with the SMC or traces to the SMC?
 
M

mccafe

Member
Yes, red probe on ground.

I checked external display and it doesn't output anything here either. As soon as I plug in the charger, the monitor LED indicates a device is connected through HDMI however just a black screen. Chimes and everything still.

I also notice that for the internal display, when we get 3.3 volt pulses on the pin 18/19 the screen goes to a really dark black and then goes "neutral" black again.
 
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M

mccafe

Member
I was putting this aside for a while. I'll give the USB drive with LED a try.

One question: can failed hall sensor cause no output to external display? The customer mentioned the screen was flickering before it went black forever.
 
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