Macbook Pro 13" No Power (another one)

[skyking421]

I have another one of those 13" Macbook Pros (2010) that have no power.

Pressing the power button does nothing. No fan spin, lights, nothing. I have checked the power button operation (pins 5 and 29 on the keyboard socket) and it drops the 5v on pin 5 to zero when pressed. I guess its working.

The fuse near the power plug is good as well as the other 3? green fuses.
The charger seems to work normally. Green, then orange, then green again, showing a charged battery (I guess). Tried two chargers.

I get an occasional 19v at the battery. It seems that the charging circuit intermittently checks and sends a burst to the fully charged battery.

I tried a reflow of the Nvidia chip and no change.

These boards are selling used for about $300 and it seems to be a widespread problem.
Could it still be the Nvidia chip?

Any other ideas to diagnose this?

Thank you much for your expertise.
Richard

[skyking421]

Re: Macbook Pro 13" No Power (another one)

Just by chance, I see a tiny resistor (?) is broken off the motherboard.
If I did it, then it's an additional problem.
I don't think I did it, so maybe this is the whole problem. I bought this laptop like this.

It is part of the circuitry for part #51125. There are other resistors also connected to #51125.
It's clear to see in my photos attached.
I'm willing to try soldering a microscopic piece on again, if I can find a replacement. I do have a number of motherboards around that I could get it from.
I would need to know what it is and its value. I assume it's a resistor.

[degutji]

Re: Macbook Pro 13" No Power (another one)

Maybe you can start from here http://www.ti.com/product/tps51125 if you don't have schematic for this model. It's look like resistor 20K Ohm if we read the datasheet. I Hope it help

[skyking421]

Re: Macbook Pro 13" No Power (another one)

Thanks.
I'll start looking at that.

[skyking421]

Re: Macbook Pro 13" No Power (another one)

I'm having a hard time trying to decipher the datasheets.
It looks like my "resistor" is connected to pin#3 (vref) of the chip, but another datasheet rotates the thing 90 degrees and confuses me as to which pin is which.
Usually pin #1 is at the "dot" on the chip. Right???

Anyway, if this is pin #3, then it has a .22uF Cap connected directly to it.
Pin #2 has a 20k resistor.

Can I verify anything by measuring a voltage there?

Thanks much.
Richard

[skyking421]

Re: Macbook Pro 13" No Power (another one)

I measure 2.6v dc on the missing component connected to pin #3.
And 0v on the other side of the missing component space.
Any help?

[degutji]

Re: Macbook Pro 13" No Power (another one)

I measure 2.6v dc on the missing component connected to pin #3.
And 0v on the other side of the missing component space.
Any help?

pin #16 is VIN , measure if you get adapter voltage, start from there to find pin direction #1 . But if you get 2.6v on pin #3 ( VREF ) maybe you are on the spot , I think . Good luck

[kennethf]

Re: Macbook Pro 13" No Power (another one)

The component you are missing is an .22uF Cap

[spidey]

Re: Macbook Pro 13" No Power (another one)

tell me what is the current ?
if its less then 0.001 something is open. it migth be that resistor. You have the schematic so measure the voltage after the power "not the charging part of the circuit just after powering part(acording to charginf led is on)" check +3 +5 +19 etc.. if dont find any of them start measuring from that point to source.

"The component you are missing is an .22uF Cap"
if so, it is not. (i assume there is no current higher then 0.01A)
so check mosfets and ic's you'll find.

[tamas]

Re: Macbook Pro 13" No Power (another one)

May i ask the voltage at top of the right capacitor of 51125 please?
At me it is battery voltage and 5 v is gone if magsafe is disconnected
thanks