Switch OLED stuck in stage 2 boot

Hey folks, got here a OLED switch which stuck in stage 2 boot. No shorts on the board found. When plug in battery connector with bench PSU 0,0mA. Charging is fine. By pressing on button current draw goes up to 200mA and stuck around 100mA within 2 seconds. Found on MAX77620 1,3v rail is missing. No short found. Have here a functional donor board, so I can measure. I cannot find a datasheet for the MAX77620. Can someone tell me what does this thing exact doing? Because when 3,3v rail is present and enable signal for the 77620 is also activated it have to produce all the rails right? I checked all diode values with other board, it is exactly the same. So what can prevent this chip to produce the 1,3v rail? RCM mode not possible. Thanks

Hi waterchill,
seams you have the same issue like me with my OLED.


In the end i find out that the emmc was faulty. The emmc was a SK hynix which was dead after systemupdate. Also the 1,3V line was not on!.

YOu have 2 options: First, remove emmc from board, and solder him on a emmc pcb of a v1 or v2 which is able to start hekate.

You need the emmc stencil to reball the emmc.

Try to read the emmc with the hekate emmc backup tool. If that works, the chance to fix the issue is very high. But i guess it wont work because the emmc is dead.

The second option is to solder the emmc with the sd card hack and try to connect them to pc and read it via nxnandmanager.

Have fun and good luck


Thank you for your input. I will get this week an emmc reader which I can connect via USB to PC. No need to solder it has a socket. I will try to read the chip via nxnandmamager and will share the result. Actually it does not make sense to change the 77620.

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For confirmation I removed the eMMC from a non OLED switch and 1,3v is still produced from 77620. I don’t think that there such so a big difference between these two switches but who knows.

Makes sense. The emmc send a i call it “okay iam here” package that activate the cpu and set the 1,3 volt line to active.

If emmc dead, no signal. :slight_smile:

Its always the CPU calls max77620 to turn 1.3v on, you can verify that by multimeter or oscilloscope, when emmc removed, 1.3v will still present for short period of time when power button pressed but then cut-off when emmc no response.

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I got the reader today and the emmc looks like this. I don’t know if this is good or bad

Looks good so far. Create a backup of the emmc for sure.

Sorry for the late reply. Okay, seems the emmc is okay, please create a backup. For OLED you should solder a rp2040 in and start hekate to dump the keys.


Did the mod and got it to work with this video:

Cannot post link, but youtube unbrick switch level 1