I’m trying to power on the Switch with a lab PSU, but it stucks on first-stage boot and drawing only 80mA. In the internet I find info, that it can be a problem with a MAX77621 IC. I didn’t find any shortages near MAX77621 and MAX77620 ICs. How can I detect a faulty IC?
Check the various voltage rails, I assume you connect the nand before trying to power the board? otherwise it will get stuck in stage 1 at around 0.08a
Yes, nand is connected.
Rails near ENXX:
3v3 - 1.05v
1v8 - 1.05v
Rails near MAX77620:
VDD_CPU_1v1 - 0.17v
VDD_CPU_1v0 - 1.00v
VDD_1v3 - 1.35v
VDD_CPU_1v8 - 0.50v
VDD_1v0 - 1.05v
VCC_3v3 - 1.05v
VCC_2v9 - 0
VCC_3v3 - 1.05v
VDD_1v05a - 1.05v
VDD_1v05a - 1.05v
VDD_1v05b - 1.05v
I think it looks really bad…
Yes you have multiple shorted rails, look for physical damage on the max77620, same for the ENXX ic on the back of the board above the audio ic, that enxx ic delivers the 3.3v.
Upload images that are close up to the ENXX, max77620 and the max77621 below the apu
I would take note of the resistance to ground on each rail and not power on the board anymore until you can track down the issues
I think it will be a problem with max77620 IC, but I can’t say if it is a problem with my soldering skills or a problem with the IC, that I bought from China and in the soldering process it started to peeling off a top (paint?) layer of IC.
And where can I find template images, those are used to note diode measurements?
It’s very difficult to see what is and is not a bridge in those images
The max 77620a does have a coating on top but even so it looks rough, so the one in the image is the replacement? how did you flow it into place? doesn’t take much of a nudge to cause bridges under the chip
I think you should go over everything and make sure no components are bridged
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your 77620 is completely toast due to poor rework. Pull it and place a new one on but be far more gentle this time, they are extremely fragile, essentially a glass substrate. Your audio IC is also looking like its trashed as well and a faulty one can here can prevent boot as its tied into the 3.3v rail. Id look into replacing this as well.