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Old 06-02-2022, 10:35 PM   #1
duwane
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Default Apple 85W MagSafe Power Adapter - blown - help with component identification

Hi All.

I have an Apple 85W MagSafe Power Adapter (Model No: A1343) that has a blown power MOSFET (Q050 - Infineon IPP60R299CP - - all 3 pins dead short). When the FET blew it took out an SMT resistor, as well as possibly vaporizing an entire capacitor and its pad (see attached photos). Hopefully that will be all that is blown, but until I can replace the FET and the other physically damaged components I can't tell.

The burned resistor and cap in question are located underneath the large main cap (as seen in 2nd and 3rd images).

Is anyone able to measure what the value of R051, and confirm if C052 is actually a NO STUFF? By the looks of the remaining pad for C052, it could very well be a NO STUFF as the solder looks undisturbed. Just weird that one pad would vaporize if there was no component there. I have cleaned off most of the carbon in there (there was a lot!) for the photos.

Attached images to help identify and/or locate the components I am referring to. In the first image I am showing the board layout with the main cap in the top left. In the second image, I have bent the main cap upwards to see the other components underneath that are damaged/burnt. Third image is a closeup of the burned area and damaged components.

I am hoping someone either has a schematic, or is able to identify the components, or if someone has a working adapter to see what the values are that would be greatly appreciated.

Any and all help appreciated, and thanks in advance.
Attached Images
File Type: jpg 20220603_140808-1.jpg (324.0 KB, 22 views)
File Type: jpg 20220603_140842.jpg (419.0 KB, 26 views)
File Type: jpg 20220603_140842-1.jpg (447.9 KB, 25 views)
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Old 06-03-2022, 12:22 PM   #2
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

My compliments for the clear pictures.

The first two characters on the fried resistor appear to be "R" and "1". The third character could be "0", "8", or "9". I'm guessing this resistor is in the Source circuit of the switch MOSFET, a current sense resistor. .10 or .18 ohms seem the most likely possible values.

I think that capacitor location was unpopulated, for the reason you mentioned. On the other hand, it looks like the trace near the "C" of the reference designator started to fuse. At the least, it will have to be reinforced. That partial fusing means that the trace was carrying significant current until something else opened up first. The cause of the MOSFET shorting may yet be in the adapter. Lite On is a good power supply company.
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Old 06-03-2022, 04:27 PM   #3
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Usually when a mosfet source resistor is open, the drive/controller ic is also damaged because the ic's CS pin can see very high voltage as the resistor goes open. There is likely a small resistor between the mosfet source and the controller CS pin
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Old 06-03-2022, 05:49 PM   #4
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by PeteS in CA View Post
My compliments for the clear pictures.
You are most welcome. Thank you for trying to help out. It makes sense to post clear pictures so that people can actually help. No point posting potato cam pics, and expecting much assistance

Quote:
Originally Posted by PeteS in CA View Post
I'm guessing this resistor is in the Source circuit of the switch MOSFET, a current sense resistor. .10 or .18 ohms seem the most likely possible values.
Yeah I thought a low value too, but it still gives a reading of 19.6k ohm on the multimeter, so threw that thought into doubt. Also with the amount of heat it appreas to have taken, I don't trust its current reading.

Quote:
Originally Posted by PeteS in CA View Post
At the least, it will have to be reinforced. That partial fusing means that the trace was carrying significant current until something else opened up first.
Could just have fused due to heat from the resistor maybe? Just hard to beleive that even the pin end of the capacitor would dissapear entirely, so at this stage the only logical explanation is that there was never any capacitor there.

Quote:
Originally Posted by PeteS in CA View Post
The cause of the MOSFET shorting may yet be in the adapter.
Pretty common for power FET's to die based on my experience. Can be caused by voltage spikes, weakness in the junctions inside the chip itself, etc., but yeah hoping its nothing more than just the FET and resistor lol
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Old 06-03-2022, 06:02 PM   #5
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
Usually when a mosfet source resistor is open, the drive/controller ic is also damaged because the ic's CS pin can see very high voltage as the resistor goes open. There is likely a small resistor between the mosfet source and the controller CS pin
Thanks for helping out.

The reistor still reads 19.6k ohm on the multimeter, so luckily didn't die OL, so I am hoping that the drive chip didn't get hit too hard. I don't trust this reding though, as the resistor must have gotten really hot to burn the paint off and melt the track pad and solder next to it.
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Old 06-03-2022, 06:28 PM   #6
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by duwane View Post
Thanks for helping out.

The reistor still reads 19.6k ohm on the multimeter, so luckily didn't die OL, so I am hoping that the drive chip didn't get hit too hard. I don't trust this reding though, as the resistor must have gotten really hot to burn the paint off and melt the track pad and solder next to it.
That source resistor is OPEN, it should read LESS than 1Ω, not 19k! The Source resistor connects the mosfet source lead to ground. Now as far as the circuit operation, the resistor I was referring to is a different one. And I will bet money that the ic is blown.
Here is a simple smps, Rcs is your burnt resistor, Rcsf is the one I am referring to.
The drain of the mosfet has a min 160vdc, when the mosfet shorts D~S and the source resistor goes OPEN, approx. 160vdc is applid to CS (most ic's can handle about 5v on this pin)
Another path to ic destruction is a short D~Gate, then 160v is applied to the OUT of the ic, it can't handle this.

This is just a sample circuit, your ic etc. will be different but similar in operation.
Attached Images
File Type: jpg smps_diagram.jpg (159.6 KB, 9 views)

Last edited by R_J; 06-03-2022 at 06:40 PM..
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Old 06-03-2022, 07:12 PM   #7
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
That source resistor is OPEN, it should read LESS than 1Ω, not 19k! The Source resistor connects the mosfet source lead to ground. Now as far as the circuit operation, the resistor I was referring to is a different one. And I will bet money that the ic is blown.
Here is a simple smps, Rcs is your burnt resistor, Rcsf is the one I am referring to.
The drain of the mosfet has a min 160vdc, when the mosfet shorts D~S and the source resistor goes OPEN, approx. 160vdc is applid to CS (most ic's can handle about 5v on this pin)
Another path to ic destruction is a short D~Gate, then 160v is applied to the OUT of the ic, it can't handle this.

This is just a sample circuit, your ic etc. will be different but similar in operation.
Roger that, thanks, and thanks for the explanation. I will pick up some controller chips as well just in case. They seem to be relatively cheap on AliExpress, so will replace this as a precaution as well.

When I measure the uquivalents of RBleeder, and RG on your example curcuit, they both read as OL but show no signs of heat damage (they are on the underside of the board), so may end up having to replace them as well.
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Old 06-03-2022, 07:24 PM   #8
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

What is the controller number in your power supply?
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Old 06-03-2022, 07:36 PM   #9
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by r_j View Post
what is the controller number in your power supply?

lta910n
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Old 06-03-2022, 07:46 PM   #10
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

I can't find a specific datasheet for the LTA910N chip, but I did find this PDF on the manufacturers website when I search for LTA910N:
https://www.nxp.com/docs/en/data-sheet/TEA19161T.pdf

It seems that the LTA910N chip interacts with the other chip on the board (TEA1762)
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Old 06-03-2022, 07:51 PM   #11
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Found the datasheet for the other chip on the board:
https://www.nxp.com/docs/en/data-sheet/TEA1762T.pdf
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Old 06-03-2022, 08:03 PM   #12
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Took a photo of the underside to show what I am talking about.

Circled in red is the LTA910N, and TEA1762.
Circled in green is where I have now removed the FET from.
Circled in yellow are the 2 resistors (RBleeder, RG) that also seem to measure as OL, so assuming they are also damaged.
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File Type: jpg 20220604_135531-1.jpg (740.5 KB, 10 views)

Last edited by duwane; 06-03-2022 at 08:06 PM..
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Old 06-03-2022, 08:10 PM   #13
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 (1N4148) may be damaged, These are in the gate circuit.
The 4.7Ω and the diode are across the 100Ω, these components are between the mosfet gate and one of the ic pins, Can you see which pin it connects to? likely either pin 10 or 12

Last edited by R_J; 06-03-2022 at 08:25 PM..
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Old 06-03-2022, 08:15 PM   #14
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 may be damaged, These are in the gate circuit.
T4 diode seems to be fine, It measures 0.565v drop in one direction on diode tester, and OL in the other direction
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Old 06-03-2022, 08:16 PM   #15
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 may be damaged, These are in the gate circuit.
What wattage would you say those 2 resistors are? Also trying to decide what wattage the unknown resistor might be as well.

Last edited by duwane; 06-03-2022 at 08:23 PM..
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Old 06-03-2022, 08:32 PM   #16
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by duwane View Post
What wattage would you say those 2 resistors are? Also trying to decide what wattage the unknown resistor might be as well.
The two gate resistors are low wattage (1/8w?) the other one might be around 1~2 watts? being very low resistance the wattage won't be to high. measure it's physical metric size. You will need to know the resistance as it is important to the operation as the current through this resistor controls how the circuit operates

Last edited by R_J; 06-03-2022 at 08:37 PM..
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Old 06-03-2022, 08:52 PM   #17
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
The two gate resistors are low wattage (1/8w?) the other one might be around 1~2 watts? being very low resistance the wattage won't be to high. measure it's physical metric size. You will need to know the resistance as it is important to the operation as the current through this resistor controls how the circuit operates
Yeah thanks. Hoping to find that value. After looking at the numbers on the unknown resistor again, my guess is it says "R170" which would be 0.17ohms. Still hoping that someone can confirm if they have one of these sitting around somewshere.

I am working through using the measurements of each one to get package number. I guess I could just buy the highest available wattage with the same package number.
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Old 06-03-2022, 09:01 PM   #18
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Try cleaning that burnt crust to see if the other numbers are reviled

Last edited by R_J; 06-03-2022 at 09:06 PM..
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Old 06-03-2022, 09:10 PM   #19
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
Try cleaning that burnt crust to see if the other numbers are reviled
I tried, but the parts that are not visible are actually missing/burned paint. I just removed that resistor, and it has a crack right through it (it fell into 2 pieces when I desoldered.
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Old 06-03-2022, 11:07 PM   #20
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Default Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

Quote:
Originally Posted by R_J View Post
Can you see which pin it connects to? likely either pin 10 or 12
Sorry, only just saw this. It connects to pin 13. I have taken another photo now that I have removed the 2 resistors, the FET, and the IC.

There was some sort of hard underfill in a circular blobs under the chip which I can't remove, so its not so clear or easy to see. Sorry. The exposed tracks were underneath the fill.
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File Type: jpg 20220604_170250.jpg (885.1 KB, 11 views)

Last edited by duwane; 06-03-2022 at 11:55 PM..
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