820-3115-B boots about 1/3 into progress bar then hangs

[2informaticos]

You MUST remove SPI chip U6100 and reprogram it with external programmer; connected to another (Windows) computer, through USB.
CH341 programmer is about 5 bucks and is good enough...
When you get the programmer, let us know if need the BIOS dump with clean ME.

 

[jurgenkoppen]

So I now have my EEPROM BIOS USB Programmer CH341A + SOIC8 Clip + 1.8V Adapter + SOIC8 Adapter at hand.
I also have my bios update folder with ImUpdate, SFlash16, and 128MBDOS IMG File. I am trying to the best of my current still very limited understanding to figure out the next step without doing damage.
Could I please have a pointer on how to proceed?

 

[2informaticos]

You don't need 1.8V adapter in this case.
Upload somewhere your BIOS backup.

 

[jurgenkoppen]

Still keep googling for a good video in English to do these jobs on a MBP: Make a bios backup, and how to properly use the the re-programming tools I now have. There is not much out there...at least in language I can understand.Also wonder if I still need to unsolder the chip, given that I have my handy connector wires which can clamp on the chip and tie to the USB. I 'll keep looking....

 

[2informaticos]

Don't waste time with the clamp.
Remove the chip and place it in SOP8-DIP8 adapter.
Then read and save the content (backup).
Verify two times if chip content and saved backup are identical.
Do NOT erase the chip before verify is done.
Upload somwhere the backup and wait to get back the correct file.
Erase chip and write new BIOS dump.

 

[jurgenkoppen]

Thank you for giving me something intelligible to proceed with, 2informaticos.

 

[jurgenkoppen]

Before I venture into the BIOS reprogramming, which is still quite scary/vague for me at this point, I decided to have a look under the logic board to see what I might find, and to check the power rails: So far I found amongst the regular chips:
1 Potato chips in a bed of dust,
​​​​​​PPBUS_G3H: 12.59V
PP3V42_G3H: 3.493V
PPVRTC_G3H: 3.33V
PP5V_S5: 2.22 V on various test points,
Then I nearly burned my finger on L5801 which is on PP5V_S4_P18V5S5 ( Booster for sensors) , which showed OL across the coil and short to ground on both sides.
Could this be the culprit, since the Apple logo is showing up and the bar is getting to the 1/3 point points to passing the first part of POST just not able to get to the second phase when the dedicated GPU and its drivers are loaded (NVIDIA GeForce 320M) That last sentence did not come from me, but does make vaguely sense to me....

 

[2informaticos]

Remove R5805 and test again 5V_S5.
If you get correct value, then see if you get into OSX.
If yes, resolder R5805 and dig in U5805 area.
If L5801 still hot after disconnect trackpad cable, U5805 need to be replaced; or trackpad will not move the cursor.
Also check D5802.

So, don't touch BIOS untill solve this problem...

 

[jurgenkoppen]

I removed R5805, which resulted in fluctuating voltage measured at P2 of the removed R5805, as well as on P1 of C5800 /L5800 respectively. At first reading it was 2.7V, a minute later it had gone up to 3.8V only to go down again a minute later to 2V and ending up at 0V. D5802 is now also at 0V. Things were heating up at first measuring, noticeable at Q3510 and at U5701 but that has now stopped...Can you make any sense of this?

 

[jurgenkoppen]

Shall I put R5805 back in to see if it I at least get some voltage back these C5800 and L5800?

 

[2informaticos]

What is the voltage for pin17/U7200?
And resistance to ground too.

C/L5800 are both connected before R5805.
You can remove L5800 to see if that helps.

 

[jurgenkoppen]

I measured P17 on U7200 , it shows 0V. There also is no short to ground , it shows OL in Diode Mode.
The next task you gave me I is very confusing to my noob brain: Neither L5800 nor C5800 are present on my board!!! There are the pads where they belong, according to my boardview, but they look like they never had seen any solder. (This is now the second time where I run into this in my learning about board repair, ie: where boardview and schematics clearly state that that there should be a component, but nothing is there) Obviously here is something I am not getting (yet) , besides L5800 and C5800. They must exist as they are in line to PP5V_5_CUMULUS, going to the IPD Connector J5800. ????

 

[2informaticos]

Some components are oprional, don't worry about them...

Pin 17/U7200 is the 5V_S5 output; you MUST have voltage there.
I the same rail which goes to R5805.

Post some voltages for U7200, 16, 3, 8, 13, 6, 17 (again).

 

[jurgenkoppen]

As I mentioned in post 29: After I had removed R5805, it resulted in voltage first increasing and then decreasing over a minute or so to 0V. (measured at P2 of the removed R5805, as well as on P1 of C5800 /L5800 respectively). At first reading it was 2.7V, a minute later it had gone up to 3.8V only to go down again a minute later to 2V and ending up at 0V.

Regarding U7200 today:
P17: 0V
P16: 12.72V
P13: 3.06
P3, 6, 8, and all other pins = 0V

Something packed it in evidently, after I had removed R5805.

Optional components....OK, one day I will understand...

 

[2informaticos]

First check resistance to ground at 5V_S5 line.
Be sure didn't make short in some point to ground, when removed R5805.

Now seems to miss SMC_PM_G2_EN; confirm that.

 

[jurgenkoppen]

I checked resistance to ground for the 5V-S5
at the former R5805 contact points P2= 0.4 ohm, at P1= 5.3ohm
It looks clean where I removed the resistor I see no damage which might cause a short. I can send a picture of area if that helps.
I measured SMC_PM_G2_EN at U7941, and there it voltage is present at P2= 3.51V.
While there, I measured the other contacts on U7941 as well, they are all 0V except for P1=3.51V and P3= 3.35V

 

[2informaticos]

"P2= 0.4 ohm"
Check why...
You still have short on 5V_S5, even lower like before.
Should be easiest to find it now, injecting voltage.
Maybe U7200 got bad.

 

[jurgenkoppen]

Thank you 2informaticos.
This will be the first time I fire up my new DC power supply, and I am a bit nervous since there is so much I do not know yet.
If I am going to inject 5V on 5V_S5 would you tell me where would be a safe point to to so? I just want to make sure I do not make it worst...

 

[2informaticos]

You cannot inject 5V into 0.4 ohm; that means more than 10A...
Start with 1V and go up, maintaing ampers bellow current limit; 5A for usual bench power supply.