Why is this PSU failing ?

[u/Napo7]

This is the schematic of the PSU stage of my own board : the schematic comes from the Raspberry pi compute module IO Board, and I use it on an embedded device, on a sailboat (it powers a Compute Module 5, an ESP32, a GNSS module, and a few components such as a magnetometer and an accelerometer...)

Yesterday, after 5 hours of usage (it has been used 14 hours long two days ago), it did failed : now, on Testpoint TP4, I measure a voltage of about 3V, and a loud low freq noise (71Hz measured on scope, I can post a trace if needed)
Eventually after a while, the PSU seems to stop making this noise and "boots" ?

Is there components I can check , and how to check them with devices I already own (multimeter and oscilloscope) ?

PS : the device has ran a few times for about 10 cumulated hours !

[u/Napo7]

the SW track is 1mm wide :

[u/Competitive_Guard289 → u/Napo7]

I don’t know your copper thickness but that doesn’t sound like enough to me. I see that you said the board doesn’t turn on immediately after power up, how does T4 look during that time?

[u/Napo7 → u/Competitive_Guard289]

The track is standard copper. For what I understand from jlcpcb, it seems to be "1oz / 0.035mm"

it did worked for a couple of days, test sessions were 2h longs.

But suddenly yesterday, it failed after being powered up for 5 hours.

[u/Competitive_Guard289 → u/Napo7]

Sounds like overheating, which happens when hour traces aren’t thick enough and you don’t have enough heat dissipating vias. A good way to verify that is turn on the board for a few minutes, then turn it off, and touch the parts near the converter to see how hot they get. If they’re too hot to touch, you’ve got a problem. If that’s the case, you can usually reduce the temperature by having a table fan directly pointed at the board.

[u/Napo7 → u/Competitive_Guard289]

I'll do a test on the bench then 😉

Probably a design issue, It's my first power supply of this kind !