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820-00138 question about the U7310

Patricia

Patricia

Member
Hi to all you nice and smart people

I just have one question

I am working on one 820-00138 and I do not trust completely the brd and pdf I have on it .
Long story short it doesnt turn on and upon a close inspection under the scope I found that the u7310 has a lot of pins non soldered
that is the closest explaination I have , pins 1 2 4 6 7 do not have any contact at all !!!!
According to the documents only pin 6 is unconnected , am I reading this wrong or ....
No liquid damage .
I was just moving this board from one chassie to another and it worked before but now dead ... PPBUS_G3h is 12.59v and pp3v42_g3h is 3.41v i will continue to check the other rails.... it takes only 17 miliamperes on the supply ...
Thanks in advance
 
J

JohnB8812

New member
U7310 is likely fine. Are you using a KNOWN GOOD OEM 85 watt Magsafe 2 charger? Tried with all peripherals disconnected?
 
2informaticos

2informaticos

Administrator
Staff member
"pins 1 2 4 6 7 do not have any contact at all"
Do you mean bad solders, or missing pads from PCB?

If board worked before, disconnect any cable in the new case.
Test the board alone, use just USB mouse to confirm activity.
If works, then connect the cables one by one, untill board doesn't start.
 
Patricia

Patricia

Member
HI John and thanks for your reply
yes I have tried with 3 different original (dont use knock offs :) chargers and they are all 85w and same result .
It is driving me crazy since the client turned it on and it worked just nice . I just took it out and put it in the new chassie (english is not my strong side) and it is comletely dead grrrrrrrrrrrr
I did disconnect the battery before (I always do that ) and stone dead .... the board that was there before had restart issues and the client was tired of that and thats why he bought this one .
Well from full working board I have managed to get a completely dead one , great work ....
 
Patricia

Patricia

Member
Hi 2 informaticos

it is hard to explain but it seems like they never have been soldered at all to the board !!! I would take a photo if I just could get the shitty amscope mu300 to play ball with me , I have only a black screen ...
not my day
they look like brand new and no joints at all (the pins)
the board is on the bench and nothing is connected at all .....
 
Patricia

Patricia

Member
Thanks John I will in a couple of minutes
here is a photo (the best result I could get of the U7310
 

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Patricia

Patricia

Member
Here are some measurements

PPBUS_G3H 12.59 v
PP3V42_G3H 3.41 v
PPVRTC_G3H 3.41 V
PP5V_S5 - ? i couldnt find a test point because my boardview and the board itself do not look exactly the same so the pin 18 on J4800 does not look the same on my board.
PP3V3_S5 0V
PM_BATLOW_L 0v
PP3V3_SUS 0v
PP5V_S4 0v
 
J

JohnB8812

New member
PP3v3_S5 0V. That is a problem. Post voltage on C7505. If 5 volts, troubleshoot the 3v3_S5 issue. If 0 volts, post voltage for SMC_PM_G2_EN
 
Patricia

Patricia

Member
Thanks John

the C7505 is 5.03v so I come to the troubleshooting of PP3V3_S5 ... :) I am new to this so bare with me :) am I right that it is created by U7501 ?
 
J

JohnB8812

New member
Ok so you have a short on PP3v3_S5. Just making sure, the die on U1100 is ok? You have a short for sure on PP3v3_S5, so you will need to inject voltage into that line to find it. Start voltage low around 1 volt and slowly increase to 3.3 if necessary.
 
Patricia

Patricia

Member
Great John ( it isnt great but I men thanks)
I will inject voltage and take out the Flir to see what happens ....
It is amazing how from completely working board I managed to get a dead one ..... well I am blond so .... :)
Lets just hope I can get it working again or I will in 12 hours have a very angry client on my neck ....

Thank you so much John and 2informaticos
 
Patricia

Patricia

Member
It should be but .... now you will laugh .... as said I am new to this and I have a problem :) My power supply does not want to stay at 1v . I soldered the wires to inject voltage and set it to 1v but as soon as I start it it falls down to 0.14 v and stays there .... no matter what I put on the voltage it falls down to 0.14v at once... at that voltage nothing gets hot .... it is a Korad KA3005D ...
I did not enable the voltage protection , no protection is activated ... still 0.14v grrr
 
2informaticos

2informaticos

Administrator
Staff member
If there is a pure short to ground, board tries to sink more than 5A, even at 1C.
5A limit bench power supply doesn't help in this case.
Its protection is triggered and will not inject anything.
I recommend to get 20-40A for such case, like here
https://www.ebay.es/itm/480W-power-...var=563854956982&_trksid=p2060353.m1438.l2649
20V/20A, or even 12V/40A.

Lift now L7560 and check which pin the short remains.
If is on C7592, then remove U7501 and check again.
BE AWARE, do NOT power up the board WITHOUT U7501; just check for short!
If still short on C7592 side, then you need to inject voltage and find the culprit.
Remove CPU heatsink when you do that.

However, before inject voltage, check for short at L7430 and L7630.
If one is shorted to ground, at same time with L7560, dead CPU 99.99%...
 
Patricia

Patricia

Member
Thank you 2informaticos
And I just bought a very very used Farnell PDD3502A for 200 :) thinking it is old and maybe has less protection :) I will order the one you recomended .
I will do all you told me to do and see what the result will be .... just hope I didnt kill somebodys board just by taking it out and putting it back in another
chassie ... and it is 16GB just to make everything worse....

Thanks
 
Patricia

Patricia

Member
wooow bad news for me ......lifted L7560 , short still remained and it was on the C7592 side ...... lifted the U7501.... short still remained ....
Before I inject voltage i checked the L7430 no short but the L7630 is shorted ... should I inject voltage at all or should I consider the cpu dead ?
It was working perfectly when I got it .... this is a mystery for me ....
 
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