Hi everyone, on my EDM-20 board, I measured the impedance at the RAM switching regulator, and it fluctuates between 160 and 200 ohms. From what I understand, it should be around 40 ohms.
Where should I continue looking for the fault?
The UART output shows the following error:
25.04.2026 14:51:33 80810001 Severe
PowerSequence - Power Sequence Error - General Power Failure
(Peripheral, GDDR6, APU, Data Line Short)
Thanks a lot!
The resistance to ground depends on the RAM manufacturer. I guess your GDDR6 RAM chips are Micron, where I would expect ~190 Ohm. Samsung chips would read resistance to ground ~40 Ohm.
Are there more UART codes?
Please provide the whole UART error string.
Yes you are right , manufacturer is Micron.
It is alway´s the same errorcode. After i cancel error code list i get this:
[*] Operation: Run Read Error Codes
[Slot #] [Date Time] [Error Code] [Priority] [Error Message]
00 25.04.2026 14:51:33 80810001 Severe PowerSequence - Power Sequence Error - General Power Failure (Peripheral, GDDR6, APU, Data Line Short)
|-(OK 00000000 80810001 FFFFFFFF FFFF0023 00000100 216D 0036 FFFF 0000:D8)
Click for TSB Information
01 25.04.2026 14:51:33 80810001 Severe PowerSequence - Power Sequence Error - General Power Failure (Peripheral, GDDR6, APU, Data Line Short)
|-(OK 00000000 80810001 FFFFFFFF FFFF0023 00000100 216D 0036 FFFF 0000:D8)
Click for TSB Information
02 25.04.2026 14:51:33 FFFFFFFF Low No Errors
|-(OK 00000000 FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFF FFFF FFFF FFFF:5A)
Click for TSB Information
At power-on, the thermal camera shows that the SSD controller is heating up, and the GDDR chips also heat up briefly, but the NAND ICs do not heat up.
Could this be a clue or indication of the fault?
The sequence number is ‘216D’ = ‘Main SoC Power ON Cold Boot’
with the APU temp ‘FFFF’ = ‘no value’ it seems that the APU isn’t turning on.
I guess the APU core isn’t showing any heat.
Yes, there is no noticeable heat coming from the APU.
Could the APU be faulty?
It is possible. But I would check if there are any issues with the voltage lines for the APU. Maybe one line has a short or is missing.
The voltage should appear at least for some seconds after start button press.
Hi @Calvin i have a EDM 02X board. Is the green arrow the right point for the APU Powerline? there are 0,8V at Startup.
@Calvin Please excuse the mistake — I marked the points incorrectly.
I measured again, and I do have all the Power ON voltages as you specified. They are present for about 200 milliseconds during Power ON measured whit oszilloscope.
And on the other side both lines are present (VCore and VGFX)?
The both lines on top are VCore the other six are VGFX.
I guess you meassured on both lines 0.9V.
If so, I have no ideas why the APU isn’t turning on. 
Yes on booth lines as shown on picture.
If anything else comes to mind, I would be grateful for any further advice or tips.
But thank you very much for your help and involvement so far.
