Hi,

The resistance on those two coils is quite high. It starts at around 20kΩ when I begin the measurement and gradually increases to 140kΩ, after which the resistance continues to rise very slowly.

Looking at the datasheet for the AOZ1212, on page 7 under Output Voltage Programming, the formula is:

V = 0.8 × (1 + R1/R2)

I removed both resistors from each buck regulator and measured them. The readings are consistent across both:
R1 = 140kΩ and R2 = 20kΩ
So:
0.8 × (1 + 140/20) = 6.4V — which is what I have measured. ...

Hi everyone,

I’ve got a Ubiquiti switch (model US-48-500W, motherboard: USW48P_BCM) on my bench. The switch powers on, but none of the LEDs next to the LAN ports light up.

I’ve measured voltages across the board and suspect a problem with the 12V rail. At the coils where I’d expect 12V, I’m seeing around 6.3V. One coil shows a stable 6.378V, while the other fluctuates between 6.270V and 6.310V.

All other voltages seem fine — 1V, 3.3V, and 5V are present and match the expected values.

I've replaces both buck regulators already (AOZ1212)...