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Old 06-03-2023, 12:47 PM   #1
giove
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Default problem with keyboard macbook a1297

Hi, I have a macbook a1297 emc2414 motherboard 820-2914-B with password prompt on startup. I unmounted the bios chip and reprogrammed deleting everything after $SVS from the binary file. After reassembly it boots normally with the operating system. Unfortunately, probably by disassembling the motherboard, the keyboard no longer works.
I have unplugged and plugged the connector several times but nothing to do not even the start button works. To start it I have to disconnect the battery and put the power supply connector. Is it possible that the keyboard broke? do you think replacing it works? I have many doubts because before disassembling the motherboard at least the power button worked ...
Also what is the keyboard pinout to locate the Power button?
Thanhs
Roberto
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Old 06-04-2023, 06:54 AM   #2
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Default Re: problem with keyboard macbook a1297

See attached.

1) In the absence of the keyboard, the PCB designers have left shorting pads on each side of the PCB which can be used to emulate a power button using tweezers.

2) The keyboard & trackpad functions are mapped to a USB port on a USB hub. The actual keyboard and trackpad USB functions are handled by a Cypress PSOC chip = 8051 or Cortex M0 processor with USB interface.

3) Start with the usual power rail checks on the keyboard connector. Be sure that you are inserting the flex cable deep enough into the keyboard FPC (blade) connector. Be sure that the flat bar is in the open state (use 2 hands and finger nails to open the wimpy black bar - going from memory here) -> then insert the cable as deep as it can go -> then close the flat locking bar to compress the contacts onto the FPC cable.
Attached Images
File Type: png kbc_connector.png (132.8 KB, 6 views)
File Type: png power_button_pads.png (42.0 KB, 4 views)
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Old 06-04-2023, 11:25 AM   #3
giove
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Default Re: problem with keyboard macbook a1297

ok then by grounding pin 5, which is at 3.4Volt, the macbook turns on correctly and turns off keeping pin 5 grounded. I noticed that by pressing the power button the voltage on pin 5 drops from 3.4V to 1.7V. Is the resistance probably too high? Is it a keyboard problem?
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Old 06-04-2023, 04:27 PM   #4
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Default Re: problem with keyboard macbook a1297

Yes, it appears that the keyboard contact is not a perfect one where when it is pressed, should be a hard short to ground to power this board ON/OFF. Perhaps some dirty contact?

Consider a work around and apply a resistor from SMC_ONOFF_L to ground. You will have to experiment with the values. Test with 1k, etc.

The idea is to pull-down this voltage level which then will also allow for the keypress to yet further lower this voltage so that the ON/OFF functions.

Somewhere on this forum is a thread with the same fault and the tech posted the value that worked for him. Same fault / same fix (going from my fading memory).
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