I got a buck converter from Amazon. This- https://www.amazon.com/MCIGICM-step-down-Converter-3-0-40V-1-5-35V/dp/B06XZ1DKF2

Now it's soldered onto a custom PCB I designed. I'm supplying it with 12V and the output is set to 5V. Total power in and out of the system is about 9W.

As soon as I start pulling power from the chip, it emits a horrible screeching sound, something in the high 10kHz range. That makes sense because it might be noise from the inductor, but here's the kicker: If I desolder the same buck convertor and instead of soldering it directly to the board, attach it using jumper wires; the sound disappears. I can also duplicate this problem with the exact same results with all the buck converters I received and it's breaking my mind a little

Any clue why? I'd like to have the chip soldered on and not floating in the air. Any suggestions on how to get out of this mess?

  • \$\begingroup\$ "any suggestions on how to get out of this mess?" What happens if you apply (thin) nail varnish to the inductors and leave it a few hours to dry out? (The idea being that it will stop the wires from rattling.) \$\endgroup\$ – Andrew Morton Dec 4 '20 at 0:32
  • \$\begingroup\$ It's one of those inductors inside its own black epoxy casing, I believe those are already filled with some kind of buffer material. Not sure if the varnish would ever reach the wires \$\endgroup\$ – rjds Dec 4 '20 at 0:48
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    \$\begingroup\$ maybe your circuit hits a mechanical resonant frequency of the component \$\endgroup\$ – jsotola Dec 4 '20 at 1:06
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    \$\begingroup\$ Try putting 1/8” or 3 mm thick foam pad between the module and your main pcb if you have the space. Use stranded wires to connect. These are amazingly cheap and the inductors are probably vibrating and exciting resonances on your main board. \$\endgroup\$ – Mark Leavitt Dec 4 '20 at 6:39
  • \$\begingroup\$ These converter modules are garbage \$\endgroup\$ – bobflux Dec 4 '20 at 8:28

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