Lenovo Z710 main powerrail is short - how much volt/amps is safe to inject

[Hw31]

i guess its the main power rails, as it has widests vias. i tried injecting voltage 1v and 1-5a but nothing is getting hot. resistance to gnd is about 0.002 or something like that(will update later). as its the main powerrail, do i raise the voltage to 19v and then inject 1-5amps? thx

[mon2]

No. The 1 volt should be increased slightly and the process repeats. Do check if the cpu under the heatsink is the fault. Best to check the cpu power rail resistance first. Often will be a shorted cap. Do you have a thermal camera? Ipa alcohol?

[Hw31]

theere is a cpu sockel and the cpu is and is removed(good old days). i have a thermal camera and also ipa. nothing is visible under the camera. i made a mistake in the OP. its 0.2ohms resistance to gnd.

[mon2]

0.2 ohms is a dead short. Would you have schematics for this unit? One approach is to remove all power, meter in lowest resistance mode, one meter probe at this main power rail with other meter probe at an inductor. What is the measurement? If you see a low resistance then then high side mosfet for that inductor may be leaky. Concern is to review the inductor linked to the CPU power rail. As noted by piernov, if that rail is showing a short then the high voltage from the ~19 v power adapter has travelled onto the CPU power rail and likely killed the CPU but do investigate. If the resistance at the CPU power rail is high then it is ok to keep escalating the voltage used for the power injection along with the current till the bad boy smokes out. Hoping it is a capacitor. Do post your findings before proceeding with the power injection at higher values.

reference:

PPBus_G3H - LogiWiki

[Hw31]

unfortunatly i couldnt find schematics for this board. what would a low resistance be? next to the cpu there are two inductors which where in the Mega Ohms. the rest of the unduxtors where around 30ohms and lower. i removed all mosfets from the board but the short was still present. soldered them back in

[mon2]

The wide traces with 0.2 ohms to ground may be the ground trace itself. That is why no component is heated.

[Stevedb]

Or the leads itself what you use or to small and can not give enough current to board. Use thicker wires

[Hw31]

The wide traces with 0.2 ohms to ground may be the ground trace itself. That is why no component is heated.

😳😳 thx mate. tps51363 was gone. short is gone. need to wait for replacment. will report.