Hello everyone,
I'm facing an issue with a HEG-001 motherboard that is unable to complete the Second-Stage Boot. I'd like to start directly with my conclusion, which is the decision to replace the MAX77621AEWI chip, and understand if it could be a correct evaluation.
Before I dive into the process that led me to this decision, I want to mention that I have a fully equipped lab where I can perform any kind of tests.
Let's begin:
Following some guides online, I tried to understand how the Boot phase of the Nintendo Switch works, and what are the important components for the console's startup.
First, I checked for a short circuit on the inductor of the VSYS line (4.2V). Once confirmed that there was no short on that line, to analyze all the components involved in the First-Stage Boot, I started by powering that line with 4.2V, and the bench power supply showed an absorption of 0.2A, indicating that the First Boot phase was occurring correctly.
Then, I went to check if all the voltages related to the First-Boot and the First+Second Boot were present (
) and they were all present. However, the V8, V11, V12, V13 voltages were missing.
Since from what I understand: the Second Boot phase is divided between two identical chips (MAX77621AEWI-1 and MAX77621AEWI-2) which also share an identical circuit, so if one of the two chips does not work, the Second Boot phase should not start; based on this reasoning, I went on to inject 1V and 1A into the circuit of the chip MAX77621AEWI-1 but I did not notice any current absorption nor heating by the chip or any component. I also tested the circuit components in diode mode but there was no short circuit.
I performed the same test by injecting 1V and 1A into the circuit of the twin chip, i.e., MAX77621AEWI-2, and I noticed that indeed the chip made the isopropyl alcohol evaporate. I checked for a short on the components that were part of the circuit and the multimeter (in diode mode) marked a short but not at 0V, rather at 0.063V (which made me assume it was a false short circuit). After removing the chip, I noticed that the 0.063V value on those components was still present. The strange thing was that I couldn't identify the heating of the chip either through a Thermal Camera or with Rosin, but only with the evaporation of the alcohol. So, I had the doubt that the chip did not heat up enough to be detected with a thermal camera or with rosin.
The question I now ask you is the following: Could it be that, even if the chip did not heat up enough during the injection phase, is it still the culprit for the failure to start the Second-Stage Boot?
In any case, I have already ordered the chip and it should arrive in a few weeks, so I have not yet been able to replace it with a new one.
Thank you in advance for the patience you have dedicated to reading this lengthy topic.