820-02098 power button broken.

Hi, got this a2442 with a broken screen. Was working well only screen cracked and power button not functioning. The previous repair shop already opened it and cut the flex cable of the power/touchID button. I wanted to test with a powerbutton of a 16" a2485, looked like the same in the schematics. After connecting it and booting it kept saying "Keep pressing the power button to go to startup option". (The popup what you receive when the power button is been pressed during boot) But I wasn't pressing anything. I saw that I connected the cable the wrong way... I connected it upside down. After disconnecting and trying to start. The laptop starts with apple logo and In 1 sec it shuts down, then starts again and shutdown down. It does this 5 times and then gives apple support logo and does nothing...

I measured all pins on JT500 in diode mode, checking for a short nothing special. I had another a2442 so took the diode mode reading and came to the conclusion that pin 7 was higher.

JT500

Known working laptop
1. 0.0
2. 0.0
3. 0.518
4. 0.0
5. 0.687
6. 0.642
7. 0.556
8. 0.496
9. 0.638
10. 0.496
11. 0.0
12. 0.517
13. 0.0
14. 0.0
15. 0.542
16. 0542

Faulty laptops same but pin 7 was 0.679. Checked on that line and found a little black spot on UT540. Decided to change it of a donor board. After replacing. The Diode mode reading was 0.600 on pin 7 so thought close enough... But still the same issue!

Now I'm out of ideas... Please advice!! THXS

Also, now when the logicboard is out of the enclosure and only connected to the amp meter. It looks like it's booting but after 15 sec turns off and restarts this proces.

Machine should start automatically when connect the charger, without JT500 connected.
This way you can discard a problem with touch ID, or power button.
You can use SV101/11 pads, instead of power button.
Of course, it also starts pressing any key, or clicking trackpad.

Yeah it starts when I connect the power but problem is that it shows apple logo and in 1 sec it shuts down and does that 5 times before apple support logo. So I can't boot... Or anything?!

Seems that actual touch ID is not the issue.
But connecting the flex in reverse way, could affected CPU data lines.

I also recommend to check for knocked off components, damaged connectors, or broken traces.
Mechanical damage is expected, when the board is removed and mounted back in the housing.

After connecting the cable the wrong way I reinstalled osx. All the way to last restart then when it restarted it went to startup options (because power button is continu been pressed) when I was choosing the startup disk it couldn't select and I had to put the power off then I disconnected the power button and the problems started...

Now even when connected cable right way or wrong way it won't go past apple logo for 1 sec ....

Is there a way to reset? Pvram or something?!?

Try DFU restore...

Was looking how to force dfu? As the power button cable is broke? Which pad do I have to short to force DFU manually on the logic board?

Never mind, found it already! SV100, short pin 1&2 or 3&4...

To bad, DFU restore did nothing! I looked like everything went well. Untill I Saw the Apple logo. In one sec it restarted again and after 3 restart again the support.com/applestore logo...

Any other suggestions???

Any help?!?

Damaged CPU I suppose...

Was fixed after replacing power button and entering dfu mode by normal way. Not force dfu...

Problem was while power button was pressed(because of power button of 16" was installed) installing Mac OS... So there was no hardware issue only de firmware or boot partition was trashed.

Everything works now