HP N91 motherboard - 3V_S5 short to ground and CPU hot

[mattpd]

This is an HP all in one, but basically a laptop.

Pretty sure the CPU is dead but I am looking for a sanity check from someone with more experience.

Dead except for the LED that indicates power adapter is plugged in.

3v_s5 rail is fully shorted to ground. Removed PL22 and the short is on the 3v_AUX_R side.

I injected 3A into the rail and didn't find anything hot at first but then took the CPU heat sink off and found that the CPU was getting rather hot. The CPU has two dies, and it's the smaller die that is getting hot.

Attaching schematics here. Can someone take a look? Page 15 is relevant. Is there any other reason for the CPU to be heating up other than a short inside of it?

[Techtiger]

Re: HP N91 motherboard - 3V_S5 short to ground and CPU hot

if it's 3V_S5 short to GND this voltage goes all over the MB SOC CPU all in one 3V_S5 required by PCH & CPU power ect you have to narrow down the 3V_S5 you can remove PJP10 PJP12 for example test all PL coils for resistance to GND

[mattpd]

Re: HP N91 motherboard - 3V_S5 short to ground and CPU hot

if it's 3V_S5 short to GND this voltage goes all over the MB SOC CPU all in one 3V_S5 required by PCH & CPU power ect you have to narrow down the 3V_S5 you can remove PJP10 PJP12 for example test all PL coils for resistance to GND

I don't think the "PJP" markings are actual components. In the area of the board where they are marked there is just a via.

[piernov]

Re: HP N91 motherboard - 3V_S5 short to ground and CPU hot

Smaller die of the CPU package is PCH. If it's heating up when injecting voltage on 3V rail, it's dead.

[mattpd]

Re: HP N91 motherboard - 3V_S5 short to ground and CPU hot

Smaller die of the CPU package is PCH. If it's heating up when injecting voltage on 3V rail, it's dead.

Thank you for the confirmation.

[NEUTRONS]

Re: HP N91 motherboard - 3V_S5 short to ground and CPU hot

Smaller die of the CPU package is PCH. If it's heating up when injecting voltage on 3V rail, it's dead.

Salut , ta remarque est intéressante, je me trouve peut être dans la même situation avec un hp 250 G5 , je ne trouve pas le schéma de la carte mère, BDL50 LA-D704P Rév: 4: 0, que dois je faire pour m'assurer que le cpu est mort , en court circuit quoi
merci d'avance