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john-seaton

Repairing the LEDs PWM

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My LEDs shorted out and blew the main board's PWM control circuitry. Simon sent me a replacement but I can't help wondering if it is repairable. If I had to guess its going to be a mosfet or transistor that has been blown and this should be fixable.

Anyone here attempted this fix before? I have the tools to do SMD work so I'm not too concerned about that and I think I found the schematic on github, I just need to make sure it matches the version of the board I have now.

 

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I'm pretty sure there's only one version of the schematic for the UM2 at this point. Any changes to the board have been parts only I suspect - the layout likely hasn't changed.

 

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Yep this should be an easy fix. J15, when shorted sends uninhibited current to ground through the NPN transistor BC817. This transistor has a max collector current of 500ma. Chances are this was exceeded and burnt out the transistor. I believe it is the SOT323 package too. Can anyone confirm?

Thanks

John

 

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