KC Micro Tronix
Member
I am working on a 820-00840-A "Came in for no backlight."
After a few quick checks the (PANEL_PWR_EN) out of U8501 never shows up. Not even for a split second. I know what part of the boot process it should show and it never does. On my reference board it does. My understanding is this should turn on and if the CPU does not get a response from the LCD or current draw is too high it will shut it down. The current draw circuitry is "No Stuff".
Then I checked. (EDP_PANEL_PWR_EN) input into U8510 and it never shows up. The power rails to these chips are present and normal.
The only thing in front of this is U0500 "the CPU" I don't suspect this part. I am lacking the understanding of this process to troubleshoot further.
Watching the board it does boot. Current draw pattern shows a booting board. Exact same pattern as my reference board. It even chimes like it is happy.
After a few quick checks the (PANEL_PWR_EN) out of U8501 never shows up. Not even for a split second. I know what part of the boot process it should show and it never does. On my reference board it does. My understanding is this should turn on and if the CPU does not get a response from the LCD or current draw is too high it will shut it down. The current draw circuitry is "No Stuff".
Then I checked. (EDP_PANEL_PWR_EN) input into U8510 and it never shows up. The power rails to these chips are present and normal.
The only thing in front of this is U0500 "the CPU" I don't suspect this part. I am lacking the understanding of this process to troubleshoot further.
Watching the board it does boot. Current draw pattern shows a booting board. Exact same pattern as my reference board. It even chimes like it is happy.