Apple 85W MagSafe Power Adapter - blown - help with components

[bastyani]

Hi, I have an 85W MagSafe Power Adapter, Model No: A1343, worked ok,
then suddenly dead. Opened it up and there are a few components blown.
Two resistors and a chip.

You can see more on the attached pictures.

Unfortunately I can only read the few last characters on the chip - an N on the top and 3261 or 5261 on the bottom (can't rally tell, the character is halfway visible but most probably is a 5261). The chip is blown right on the position where the model/type is printed. The resistors are also hard to tell.

Can anyone of you experts tell me if it is possible to source the right chip and the resistors and replace them? All other seems ok. Another question is why this happened?

Will it hipoteticaly work if those things are changed or is there a problem somewhere also and they will be blown up again?

Thank you for your help!

[techtiger]

Find out the Schematic check the pic

[bastyani]

Hi techtiger,

thanks for the schematic. As I can see the IC34 is not the same? It has 14 pins, the chip on my board has 16 pins...

[bastyani]

Maybe instead of the DAP013F it is the DAP015D?

[PeteS in CA]

My guess is that the 3-pin power device near those two blown resistors, probably a MOSFET, is shorted. If it is a shorted MOSFET, the blown IC may be in its Gate circuit and was exposed to high voltage when the MOSFET shorted Drain to Gate. The resistors look like low value current sense resistors in the Source circuit. The surge of current when the MOSFET shorted Drain to Source fried the resistors, and may have vaporized some of the trace connecting the resistors to the source, damage that would need to be repaired.

[ACS-Repair]

One thing to keep in mind here is that by piecing this back together you may be at risk of it blowing up again in the near future and potentially causing a fire. Think about whether the risk is worth just replacing it.

[bastyani]

Hi guys, thank you for the replies!

Originally Posted by PeteS in CA

My guess is that the 3-pin power device near those two blown resistors, probably a MOSFET, is shorted. If it is a shorted MOSFET, the blown IC may be in its Gate circuit and was exposed to high voltage when the MOSFET shorted Drain to Gate. The resistors look like low value current sense resistors in the Source circuit. The surge of current when the MOSFET shorted Drain to Source fried the resistors, and may have vaporized some of the trace connecting the resistors to the source, damage that would need to be repaired.

Thanks "PeteS in CA" for a thorough explanation. I was sure there must be something else wrong that blew the IC and the resistors... I will also check the MOSFET. I am also a little worried about the "vaporized traces", hopefully I will be able to fix them. Any idea on the resistors values?

Originally Posted by ACS-Repair

One thing to keep in mind here is that by piecing this back together you may be at risk of it blowing up again in the near future and potentially causing a fire. Think about whether the risk is worth just replacing it.

Thanks "ACS-Repair"! I know that, and that's why (if I manage to fix it) I will only use it as a "backup" under supervision.

[momaka]

Originally Posted by bastyani

I was sure there must be something else wrong that blew the IC and the resistors... I will also check the MOSFET. I am also a little worried about the "vaporized traces", hopefully I will be able to fix them. Any idea on the resistors values?

Could we see a few pictures of the top-side of the adapter where the components are? That should help us determine what that MOSFET is doing. It's clearly on the primary side, as the presence of the Source resistors suggests. But whether it's used for the APFC circuit (if there is even one) or the switching device for the PS, that's what we need to know.

Generally, these adapters won't blow from an overload on the secondary side, but could blow from over-temperature, high voltage spikes / dirty power from the lines, or also if the main input bulk cap has failed... which could be the case here if this adapter is old and/or was used a lot and/or has APFC.

Originally Posted by ACS-Repair

One thing to keep in mind here is that by piecing this back together you may be at risk of it blowing up again in the near future and potentially causing a fire. Think about whether the risk is worth just replacing it.

As long as the correct replacement parts are used and fuse is rated properly, it's extremely unlikely for these adapters to cause a fire. Now if it was any cheap Amazon/eBay/AliExpress "replace power" adapter, I would be worried about those even when new out of the box. But this genuine one is made by Lite-On, and Lite-On doesn't half-ass their stuff when it comes to safety and fire-hazards. So I wouldn't be worried about the adapter once repaired... so long as we can find out what went wrong and why.

[bastyani]

Hi momaka!

Yes, of course! The top side had a lot of "silicone" in there and it was really time consuming to put it all out. You have to go slowly and carefully to not damage any of the components.

P.S.: someone knows if this "silicone" is there just to "hold" the components or is it something more "special" and maybe has increased thermal conductivity to spread the heat around more evenly??

[momaka]

Thanks!

Looks like your APFC circuit MOSFET has likely bit the dust. So replacing the burned resistors and the IC likely won't solve the problem.

First step would be to remove all components that might be affected. This means the big cap and the three TO-220 components (2x MOSFETs and 1x diode) mounted on the heatsink shown in this picture:
https://www.badcaps.net/forum/attach...5&d=1618132438

For the big cap, you will need to check its capacity and ESR. APFC circuits typically blow when these reach end-of-life and go high-ESR / open-circuit. For the MOSFETs and diode - check for short-circuit on pins. In addition to that, check the input fuse, bridge rectifier, and NTC (if there is one... though there usually is.) All of these could have been taken out when the APFC MOSFET blew. In other words, time to heat up your soldering iron and start removing parts. Unfortunately, that's the only way to fix this fault... and for a power adapter like this, it may not be worth it, unless you're doing it for an educational experience.

Originally Posted by bastyani

P.S.: someone knows if this "silicone" is there just to "hold" the components or is it something more "special" and maybe has increased thermal conductivity to spread the heat around more evenly??

A little bit of both, actually.
That is, the adapter will work OK without it but may run justly a tad bit warmer internally. And if you drop it, it may not be as resistant to shock as before. But either way, it's *not* that important that you replace this silicone.