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820-00875-A Partial Power

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Alex Thayer

Member
Board hangs at 20V 0.4A after a few seconds indefinitely, or 0.5A when installed in the chassis with only the battery disconnected. All major power rails are present, trackpad clicks, no light on caps lock, no response on display. No signs of liquid damage.

I'm often unsure where to start troubleshooting when a device hangs like this, what would you recommend?
 
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Alex Thayer

Member
No blinking light activity on a thumb drive or external SSD.
No external video output.

External video test procedure: Place board in housing for hall effect sensors, with no flexes connected, connect USB-C power and USB-C to HDMI adapter while the lid is open, wait 30 seconds, close lid, image fails to appear on TV.
 
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Alex Thayer

Member
This whole BIOS programming thing is going to make me loose my mind.

I bought the TL866II PLUS

And a WSON8 adapter board

Amazon.com: QFN8 /WSON8/MLF8/MLP8/DFN8 to DIP8 Universal Two-in-one Socket/Adapter for Both 6 * 5MM and 8 * 6MM Chips : Industrial & Scientific

Amazon.com: QFN8 /WSON8/MLF8/MLP8/DFN8 to DIP8 Universal Two-in-one Socket/Adapter for Both 6 * 5MM and 8 * 6MM Chips : Industrial & Scientific
www.amazon.com

And got the official software from Xgpro, plugged in the device, successfully "reflashed" the TL866II firmware when prompted by the software...

Trying to auto detect the chip fails. When I go to self test, it fails on "ERROR #25", with or without the WSON8 adapter installed.

Am I doing something stupid or is my programmer defective? As far as I can tell it is genuine.
 
2informaticos

2informaticos

Administrator
Staff member
I don't have TL866 programmer, no idea about it.
I use Medusa for Apple jobs and CH341 programmer, when need it.

Did you try to manually select a compatible chip?
Then read and see if the dump looks like expected.
 
A

Alex Thayer

Member
Got a replacement TL866II PLUS programmer, much easier to use when it's not defective.

First I followed the instructions below to clean my ME region, no changes observed afterwards

Clean EFI ME Region - LogiWiki

We have Apple MacBook and iPhone Diode readings and general fault finding information compiled by the leaders in this area
logi.wiki logi.wiki

Then I flashed this BIOS image with a clean ME region that I found linked elsewhere on the forum, if I understand correctly I can directly flash this file without making any changes for testing purposes, again there were no changes in the device behavior afterwards

00875 clean ME.BIN

drive.google.com drive.google.com

Where should I go from here? I was encouraged by the good vcore and lack of shorts, but the cpu is starting to worry me, it appears to be the main power consumer after the boot sequence hangs.
 
A

Alex Thayer

Member
I've already done so, the board hangs at 20V 0.4A after a few seconds, no activity on anything connected. Do I need to leave it for a significant period of time (more than a few minutes) for this test?
 
2informaticos

2informaticos

Administrator
Staff member
You should get USB activity, or external video, after 30s; in some boards I got it after 5s.
If not, probably bad CPU.

Is strange that VCORE has correct voltage.
I found it to be 0.72V on working board; practically same in your case.

PLT_RST_L goes high?
 
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Alex Thayer

Member
Just left it in the exact configuration you requested for 5 minutes, nothing.

I agree, I haven't seen this behavior before on this model AND had correct vcore, not sure what to think.

PLT_RST_L goes high as soon as the USB-C ammeter jumps up to 20V, and remains high indefinitely.
 
A

Alex Thayer

Member
Yes, did that from the beginning, no change with SSD removed.

I think so as well, but any way to diagnostically confirm that the cpu is dead?
 
2informaticos

2informaticos

Administrator
Staff member
This is not an exact science.
We don't have the test hardware from manufacture line.
In general, A1708 = garbage...
 
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