betty r6_mb

[Jeff Ronnermann]

Re: Razer Blade RZ09-01953 no power

Flux and remove the 2nd mosfet. Then measure the resistance to ground again. No power to the logic board during these tests.

Also review the above sticky by piernov on charger circuits.

I have a betty r6_mb with a similar short to ground at the drain of the left mosfet, even after removing both. It stopped working after water ingress, and there are a few minor rust spots on some of the caps. Do I need a multimeter that supports capacitance to confirm which specific caps are shorted? Even if the shorted cap is identifiable, is there a way to identify the expected value without the schematic?

[mon2]

Betty?

https://www.youtube.com/watch?v=pz1rjq5emKY

To confirm, the left mosfet is the 2nd dcin mosfet on the board that is powering the main power rail? Or is it the side that mates with the DCin power adapter?

If it is the main power rail, this implies that a high side mosfet is leaking and is usually bad news. Remove all power. Meter in lowest resistance scale. Measure the resistance to ground of this same shorted rail.

What is the exact resistance in ohms?

Respectively, repeat this measurement at the inductor near the CPU on the board. Often, the high side mosfet will leak and pass onto the cpu rail, the high adapter voltage and will kill the CPU.

[Jeff Ronnermann]

To confirm, the left mosfet is the 2nd dcin mosfet on the board that is powering the main power rail? Or is it the side that mates with the DCin power adapter?

If it is the main power rail, this implies that a high side mosfet is leaking and is usually bad news. Remove all power. Meter in lowest resistance scale. Measure the resistance to ground of this same shorted rail.

What is the exact resistance in ohms?

Respectively, repeat this measurement at the inductor near the CPU on the board. Often, the high side mosfet will leak and pass onto the cpu rail, the high adapter voltage and will kill the CPU.

It's the one labelled P039, further from DCIN, not sure which exact purpose it serves in the circuit. It's measuring 0.8~1.8ohm. At PL7, which is below the GPU and to the left of the CPU, it's 2.2ohm to ground, but the smaller PL5 and PL6 above the CPU are open with respect to ground.

It's a shame with all these fuses on the board none of them blew to protect the rest of the circuit, but I guess there's only so much you can do when it's water damage.

Thanks for your prompt reply

[mon2]

Post pics of this area and label the parts you have referenced above. Fuses are slow to act. Often the silicon devices get the hit and fail before the fuse reacts.

[Jeff Ronnermann]

attached

[mon2]

Need to see a close up view of the mosfet region (P039) that was measured.

[Jeff Ronnermann]

attached

[mon2]

Review this thread (if not done already) - same case:

https://www.badcaps.net/forum/troubl...01953-no-power

[Jeff Ronnermann]

I thought i had posted in that thread, i'm not sure how this conversation wound up as a DM.

I have some replacemenet MOSFETs on the way, i'm just worried if there's a short to ground on one of them. It looks like there's supposed to be 20v there.

[mon2]

Which pin on mosfet P039 is measuring the low resistance to ground?

source (1-2-3)
gate (4)
drain (5-6-7-8)

[Jeff Ronnermann]

Like I said above, the drain

[mon2]

Inject 1 volt (not more) onto the drain pin and hunt for who is heating up.

[Jeff Ronnermann]

Inject 1 volt (not more) onto the drain pin and hunt for who is heating up.

There's no current draw and no heat on the thermal camera, even after slowly increasing the voltage, and installing the replacement mosfets.

[mon2]

Meter in resistance mode. Remove all power. One probe on the drain pin of the mosfet you suspect to be shorted. Other meter probe to ground (metal shield is ok).

What is the exact resistance in ohms?

[Jeff Ronnermann]

.8 ohms

[mon2]

Can you post a pic of your meter when you are measuring this point? Wish to review the meter scale and units of measure.

[Jeff Ronnermann]

I promise you it's ohms, not kiloohms or megaohms. 0.8 ohms.

[mon2]

Then there must be a current draw if the injection is done correctly. This is a direct short to ground or may even be ground.

ps: hate apple auto-correct