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820-3332 Display Issue

S

SMMRepair

Member
Inspect eDP connector very well; sounds like there may possibly be some slightly bent/damaged pins inside. Also compare diode values for data lines on eDP to working board; I've seen a few of these (drops I believe) that had open data lines (and sadly were not repaired). With these symptoms, you should be able to find something off in the diode readings. Make absolutely sure all filters working well; they can be bad but have continuity (rarely--they break super cleanly).

USB not working is odd and may not be related, but "might" hint at a BIOS/ME issue. Could also be SMC or MUX related; check and make sure there's no crack/break in the board near I/O ports. Of course, lots of lines there, and cracked PCB will cause funky issues due to internal shorting.
 
J

JohnB8812

New member
Ok I did notice the right side of the connector is slightly bent, so I will start with that. I may just replace all of the filters as well to rule it out because I have seen similar filter issues on iPads before. HOPEFULLY it is not a crack in the board haha that would be the worst, but I will check that as well
 
J

JohnB8812

New member
Replaced LCD connector to be safe no change. All of my DP lines on the LCD connector measure OL pins 11,14,17,20,23. Pins 9 and 10 measure 0.6. I don't have a known good 3332 to compare to unfortunately. I don't see any physical cracks to the board, but this doesn't sound good to me if all of the pins measure OL.
 
S

SMMRepair

Member
Ahh, yeah, OL isn't great news. .6 is fine, and all data pins should read roughly that. The good news is that they don't all go straight back to the CPU; all of those pins measuring OL could indicate a bad U9150. What does U9150 area look like? I'd reflow, then replace if reflow doesn't help.
 
J

JohnB8812

New member
No change after reflow. Going to need donors to replace it. Can it come from a different board or does it have firmware?
 
2informaticos

2informaticos

Administrator
Staff member
"All of my DP lines on the LCD connector measure OL pins 11,14,17,20,23."
That's correct, all data lines have serie capacitors.
You should check diode mode at pin 1 of C9020-29 caps in this case.
Be sure to have good continuity from pin 2 of them to LCD connector.
What is the voltage at pins 28-30 of J9000?
Do you get white, or black screen?
 
J

JohnB8812

New member
Ok will check that on Monday. Pins 28-30 gives me 5.1 volts. I get a black screen. As soon as you press the power button, immediate faint black screen, then flash and chime and black screen while external works great.
 
J

JohnB8812

New member
Ok finally got back to this one. Yes steady 46 volts on BKLT (it is present). 5 volts at the LCD connector. Replaced the eDP MUX U9150 and still exact same issue! Any ideas? I might replace all the filters to the screen to rule that out.
 
J

JohnB8812

New member
Let me edit this: on pin 1 I have around 0.57 on all caps. On pin 2, I have open line. Does this mean I need to jump each to the connector? Is the board cracked possibly? I don't see a crack, but that might make sense.
 
2informaticos

2informaticos

Administrator
Staff member
So backlight is present, only missing image.
That should be some problem on the eDP data lines.
Measure resistante to ground on data lines, when video cable is inserted.
The values will correspond only to LCD display, but any strange difference will denote LCD connector issue; bad/bent pins, bad contacts...

U9100 manage some LCD signals too.
I don't know if is involved in your problem, but you can change it, just in case...
 
J

JohnB8812

New member
It's definitely not the screen or LCD connector I'm using a known good tester and I've already replaced the connector. Do you think it is worth replacing U9100?
 
J

JohnB8812

New member
Replaced GMUX. EXACT same issue! This board sucks lol any other ideas? I don't think BIOS because that would make no sense if it boots externally right? I would guess GPU or broken internal trace?
 
2informaticos

2informaticos

Administrator
Staff member
GPU should control internal LCD too, when external is connected.
But internal DP output (from GPU) could be bad.

You can try some trick; using external monitor.
Just an idea, I'm not sure if you can enable iGPU in this way.
Install and run gfxcardstatus, prepare to set iGPU as default; only place cursor mouse on the option.
Then disconnect external monitor and left click.
See if internal video tries to appear at least.
 
J

JohnB8812

New member
Hmm ok I will look into that tomorrow. If it?s GPU, I may just tell the customer to try using it externally. I did give them external video back for free at minimum
 
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