Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

[Knight2000uk]

Hey guys yet another 1660 in for repair this ones got a bad FDPC5018SG which I have removed, the pad was fused to the fet so there is not much left of what would have been a pad, my question is what would that pad have connected to would it have been a grounding pad similar to the larger pad or should it have a trace going to a component, also there is a missing capacitor, wondering if anyone could give an approximate value for the cap near the other fet marked in red my esr meter gives 598uf on the board yet to desolder it off to check out of circuit.

[didi79]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Not sure what pad you are talking about. Just compare it to the datasheet https://cdn.badcaps-static.com/pdfs/...54ffabc8b5.pdf

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Thanks for your reply it's pad 10 on the datasheet, looks like it's completely gone on the board.

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Here are some of my findings, hope this may help someone in the future, the capacitor measures 10uF off board so I believe its a 16v 10uF multi layer capacitor that's missing.
I also found alternate points for the burnt pads on the flip side of the board by taking off the good fet to see how the traces are made up, the long pad pins 3 and 4 and the 10uF capacitor are all in the same circuit with continuity between the 2 pair of via points on the good fet but zero continuity on the bad one, it seems to me like the bad one fused with the ground that is in a layer underneath the board (shiny exposed spot on first pic).
Looks like I'm going to have to make some form of barrier between this point to isolate it before rebuilding the traces, any advice is welcomed.

[didi79]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Even if you can find a contact for pin10 (high side drain), it probably will not last long because the pad also serves as a heat transfer to the pcb

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Thanks for your reply, was thinking of using copper tape with a non conductive side and pcb mask between the coper tape and that area of exposed ground.

[didi79]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Thanks for your reply, was thinking of using copper tape with a non conductive side and pcb mask between the coper tape and that area of exposed ground.

Not sure if pcb mask is a good heat conductor or if it would even survive the heat cycles. But please try and let us know!

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

Must be some way of recreating what was once there surely, just seems odd for there to be a grounding pad underneath the layer of where a positive rail goes across.

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

A little update, mosfet replaced, on poking about with multimeter mem, pex and 1.8v appear to be connected to ground.

[didi79]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

A little update, mosfet replaced, on poking about with multimeter mem, pex and 1.8v appear to be connected to ground.

Jikes that sounds like its unrepairable.
Even if you grind away into the layers and fix the short, it would be almost impossible to rebuild the VRM

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

After further inspection 1.8v 5v and 3v, pex, gpu, mem... probe points have no voltage.
12v is present.

[Knight2000uk]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

I have a voltage here but it's only 0.9v this is close to the pcie slot and the 1.8v probe point, from ground the voltages are as in the photo, I think this is the 5v regulator as measuring from the 5v probe point I get voltages, however the 0.85 leg only shows 0.06v, get no readings from the 1.8v probe, any clues on the routing and likely refulators for 5v 1.8v and 3.3v, any help appreciated, the mosfet I replaced is getting 12v probing pmq1 and 2.
Any helps appreciated or any schematics to help with where voltages route from and too, thanks.

[didi79]

Re: Asus 1660 super with blown mosfet, help needed to identify pads and a capacitor

5V is usually a simple LDO, no fancy circuit around it.

No point in guessing since you almost have no voltages. Find a schematic/boardview to know what you're looking at and to know whether it is even important.

Stop poking around to find voltages. Don't even consider powering the card again! You really should focus on finding the short first before anything else.