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820-00165-A, no backlight

M

Max7

Member
Hi all,

A newbie here so bear with me if I ask something silly.

820-00165-A with no major apparent issues other than the backlight is not working, if this is the real issue.

When connected to the charger, outside the case, the flex cable is removed, drawing 530-550 mA constantly, the CPU gets warm, and the fan starts well however it reaches full speed in about 10-15 seconds.

PPVIN_S0SW_LCDBKLT_FET = 0.0v

F7700 good
R7788, R7789 are good

No EDP_BKLT_EN at Q7707, it is 0.0v, no short to ground as far as I can see
R1430 (100k) 0.0v

This is the bit I got a bit lost, EDP_BKLT_EN is generated at U0500 as far as I can say, the CPU?
PLT_RESET_L is high at 3.3v
PPVCC_S0_CPU is at 1.8v
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Do you get image for sure, only missing backlighT?
Tested external video and USB activity?
 
2informaticos

2informaticos

Administrator
Staff member
Did you test for USB activity?
If not detected, your problem is not video related.

Any history available?
PLT_RESET_L goes high?

BTW, write directly into reply box (below the last post) instead of clicking Reply button.
No need to quote an entire post, visible few centimeters above.
Please, maintain forum aesthetic...
 
M

Max7

Member
You are right, when I saw 500+ mA draw, warm CPU and fan spin I wrongly assumed that the issues was display related.

Yes, I measure PLT_RESET_L at 3.3v and if relevant PPVCC_S0_CPU is at 1.8v. How can I further check that the CPU is actually running?

Re: Replies, noted, will do.
 
2informaticos

2informaticos

Administrator
Staff member
"Any history available?"
???

Check all SPI Bus Series Termination resistors and their traces.
Inspect J6100 for corrosion.
You can try known good BIOS.
 
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