EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: xfd1001 on March 02, 2022, 06:47:00 pm
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Hello,
I have one of those cheap 24V switch mode power supplies in use for the LED lighting, it has been running 2 years but now it has come near to it's end.
The big output coil started overheating, the output is fluctuating between 23-28V, caps look all good.
Can anyone point me in the right direction?
It's a bit hard to see in the pictures due to the light; under the coil the PCB has discolored because of the extreme heat.
Update:
Found this schematic online of a similar power supply and it doesn't make any sense to me how the coil can overheat that much...
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Even if the "caps look all good", they can be bad: https://www.eevblog.com/forum/repair/help-with-power-board-of-old-bernina-sewing-machine/ (https://www.eevblog.com/forum/repair/help-with-power-board-of-old-bernina-sewing-machine/)
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Thanks for your reply and the post; I just checked the 3 output caps with my ESR meter and all 3 caps come out as good :-//
Just don't understand how it can be the ferrite; there must have been some significant current running for it to heat up this much
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Don't overlook the smaller electrolytics on the primary side, they can be a common cause of malfunctioning SMPS.
The output inductor overheating could be related to the failure, or could just be bad design and it always runs toasty.
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Wouldn't really know, but if you have some contact cleaner,
maybe you could try it on the adjustment potentiometer?