Dell Latitude 7490, no POST, no fan, LED on

[jaroslav.psenicka]

hi all,

I have a Dell Latitude 7490 here, when I connect the charger

• the powerbutton LED turns on, no fan spin (the +5V rail is present on the connector though)
• the front LED turns on
• all voltages incl. +VCC_CORE (0.8V) are on, +VCC_GT is not present
• connected USB blinks momentarily, being accessed probably
• the screen backlight blinks as well (I believe, it's very short)

after a little while (5-10 sec, maybe more)

• powerbutton LED turns off, the front LED remains on
• +VCC_CORE disappears, some rails remains present (5V and 3V)
• the CPU is not warm

may be a BIOS issue? I can't really find a BIOS for this model (DAZ40 LA-F321P REV3.0 (A02) 2018-11-08)
the BIOS may also need a service tag which I can't find, the sticker was removed...
also tried the Ctrl+Esc method with the BIOS_IMG.rcv file on my thumbdrive, no keyboard backlite
there were signs of corrosion around the USB-C port, there were a slight water damage IMO

also, a schematic and boardview for this exact model (LA-F321P) would be much appreciated
I'm using the LA-F322P version and it's not perfect

thanks,
JP