3115 changed out bad U7400, now no display and full fan 1/4 spin fixed though

[Rford]

Changed out a non water damaged U7400 ona 3115causing 1/4 fan spin. Fan now spins at full speed (at least its a step in the right direction). Problem is that it runs at full speed, and I now have no backlight/display. no obvious damage to the board, all looks well around LED driver. Is the U7400 related in some way to fan speed (like mouse issue) and/backlight? No voltage at screen connector, no display or backlight on known good screens.

 

[aprendiz]

What about external display?? Does it chime?? What voltage do you have on PPVCORE_S0_CPU_REG??

 

[Rford]

What about external display?? Does it chime?? What voltage do you have on PPVCORE_S0_CPU_REG??

aprendiz

0 v

Should that be present always? What causes that circuit to die? There was no water damage, r7510 measures correctly.

 

[dukefawks]

I bet there was nothing wrong with U7400. You actually made it worse by changing U7400 cause now there is no CPU Vcore at all. When it did the 1/4 fan spin it did have Vcore but was shutting down because of another issue.