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820-3332 mux

G.Beard

G.Beard

New member
No liquid, no impact, no visibles.

No internal display, ran ASD reports MUX IG internal switch error.

I wonder if the issue could be A1 GPU_SEL not pulling low?.... Or if it's something else I have no idea about?.. Or just a fucked chip?

What is the likely cause and solution please?

Thank you.
 
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larossmann

larossmann

Administrator
Staff member
My blame would be on the mux first and foremost. You can use a regular SMC stencil to reball one from a donor
 
D

dukefawks

Administrator
U9150 is a very simple analog MUX and ASD has no way to tell if it switched or not besides not seeing an LCD. My guess this would be an LCD/connector/eDP caps problem.
 
G.Beard

G.Beard

New member
In that case I'll just try everything I possibly can starting from the screen and working back.
 
D

dukefawks

Administrator
I still don't believe the MUX is the issue. All caps in edp lines checked? Tried a known good LCD?
Reballing would require a universal 0.5mm pitch stencil. A COMPLETE PITA
 
G.Beard

G.Beard

New member
dukefawks said:
I still don't believe the MUX is the issue. All caps in edp lines checked? Tried a known good LCD?
Reballing would require a universal 0.5mm pitch stencil. A COMPLETE PITA
Click to expand...

You may very well be right but I pulled the mux off already so now I need to stck it back on and it may aswell be a new / donor one.

From LCD connector the side I have Tested:

New LCD cable on old screen.
Known working screen.
New LCD connector.
All of the DP_INT_ etc, caps
LCD_HDP

Not tested:

LCD_FSS - not sure what that even does and the datasheet for U9100 is fucking mind boggling.
Likely I have not tested lots more I should have before I went pulling the analog mux.

Will test all, again, once some donor 3332 boards arrive.
 
Last edited:
G.Beard

G.Beard

New member
dukefawks said:
I still don't believe the MUX is the issue. All caps in edp lines checked? Tried a known good LCD?
Reballing would require a universal 0.5mm pitch stencil. A COMPLETE PITA
Click to expand...

You were of course completely correct. I've stuck the new mux back on now and it's the same.
Got a good screen in there too. Side from just replacing everything I'm clueless.

What do you think guys, please?
 
G.Beard

G.Beard

New member
So I have now replaced every cap conected to the LCD connector, stuck a good screen on it, replaced screen connector, replaced U9150 and U9100, checked all inductors.... I have no fucking idea what to look for.
 
Gurmon

Gurmon

Member
This is a good one. If you have a donor board, you may as well replace the inductors. Testing these for continuity in high speed data circuits isn't the best way to measure these.
 
D

dukefawks

Administrator
Did you verify the basics like power at L9000? Should be at least a short burst of power there after turning it on.
 
G.Beard

G.Beard

New member
backlight is 0V... Now I know what you are going to say but the OS does not know the internal screen is there. ASD reports GPU mux switching error and a light through the Apple shows nothing. And I have a working screen on there. What the fuck is going on here?
 
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