[SOLVED]Need help with placement direction of U7940 on 820-3023 Macbook Air

[brooke.j]

Like an idiot I forgot which way the U7940 goes on the logic board. I "smartly" took a picture in HDR and realized that it was not in focus to see the lettering on top. I've looked up the part ( I hope ) here http://www.mouser.com/Search/Refine.aspx?Keyword=sot891 .... doesnt give me much help because first of all it's square and second I cant really clean off the bottom good enough to see the tiny variant on pad 1 to orient it. The part has a number 2 on it and if any one can post a pic or tell me which way the number 2 faces. ..etc. Also if I've fried it can someone please let me know if I've got the right part and which one it is on that webpage. *FACEPALM

 

[aprendiz]

No Title

Hope this helps....

 

[brooke.j]

Hey there is a "-" symbol and a "0" symbol. Each above a pad. Could this mean ground for "-" That would be cool.

 

[brooke.j]

aprendiz Thanks for the help but unfortunately I need to know what pad is what on the actual part. I have the boardview and Schematics just cant figure out what the actual pins are on the part. I hope looking on the top of the actual part will clue me in. Thx bro!!

 

[aprendiz]

the dot in the corner is pin 1

 

[brooke.j]

OMG duh! Just like every other freaking part on the board. Ok I need sleep. You are the man SOLVED! I replaced this part from a working board and now the computer boots buts is soooo slow at everything. The put it back on working board ( fyi this is just for practice ) and now working board has same issue. I wonder if I got it too hot? looks fine but can you tell me if the mouser part I posted is the correct one and actually which one I should use? Thx I'm just learning and I don't see the exact amps on the schematics as whats given to me on that webpage.

 

[dukefawks]

U7940 cannot cause this. Running slow can be caused by a sensor failure or no battery/wrong battery installed. Run ASD to check for errors and check battery.

 

[brooke.j]

dukefawks Really!! I was running it off just the power supply (85w) without battery, just to practice my micro soldering skills transferring component without frying it etc. So running with no battery can cause the slow down? Thank you for your thoughtful insight.

 

[brooke.j]

Can anyone help verify the part that I will now need to get because I got the component to hot too many times. Hey I did what I planned on doing which was practice not pulling pads off and finding out how much heat these components can take. I took it off and put it on about 5 times so lesson learned. Just not that great with looking at the schematic and seeing what the differences are when buying the part from mouser.com. Here is what I have found on mouser.com http://www.mouser.com/Search/Refine.aspx?Keyword=74AUP1G3208. I'm just a little hesitant to pull the trigger.
I know it needs to be 74AUP, SOT891 (SIZE), what I'm unsure of is the 74AUP vs AUP on that page. The only thing in stock is just AUP. I'd really like to get my working board back up and running. Thank you

 

[brooke.j]

No Title

this is the schematic of the part. [h=1]U7940 on 820-3023 Macbook Air[/h]

 

[brooke.j]

ok. thank you