820-00923 small squares on internal display

Rper123

New member
Hello,
I hope to find help with this one.
Water damaged, PPBUS_G3H had short, changed U7220 and U7420. The board turns on and everything seems ok apart from bunch of small squares on internal display. They come and go constantly. The funny thing is that, when the external monitor is connected, everything is okay on both displays.
Anyone have an idea what the problem is?
 
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2informaticos

Administrator
Staff member
Check L7410/20/30 voltage in both cases.
Also see what happens playing YouTube video on internal LCD only.
 

Rper123

New member
Thank you for replay.
On all three I get 0,140V when playing Youtube video. Both when external display is connected and disconnected.
 

2informaticos

Administrator
Staff member
So VCCGT doesn't increase when image is correct on internal LCD?
I was supposing that can be related somehow.
Because iGPU doesn't require this voltage under low graphics load.
 

Rper123

New member
VCCGT does't increase on internal LCD.
Could it be U7100? PPVCC_S0_CPU is only 0,6V when only internal LCD connected. It increases to 0,7V when also external display is connected. I read in a few other threads it measures 1,2V.
Area around U7100 was also touched by fluid. I had to connect PPBUS_HS_CPU by wire because the trace was away.
 
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2informaticos

Administrator
Staff member
0.6V is correct; VCORE, as VCCGT too, are dinamicaly adjusted voltages.
And VCCGT stays normally at 0V if no graphics load is detected.
 

Rper123

New member
Okay. Do you have some other suggestion what it could be?
It confuses me that connecting external display the graphical error is away. I had a thought that liquid came under CPU causing this but it doesn't make sense.
 

2informaticos

Administrator
Staff member
When external monitor is detected, iGPU settings change somehow.
So your problem should be CPU.
Run RAM stress/test, as graphics benchmark too; when external monitor is connected.
 
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