Electronics > Beginners
Cheap chineese power supply missing short-circuit protection
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dominicM:
So I got this S-400-12 power supply to hack into a variable supply. The hack did sort of work as I get 5V-15V bit I noticed something. Looking at the schematic my PSU seems to be missing all short circuit protection components. It's even missing thermal cut out for the fan so it's on all the time. Looks like they just took everything out that's not absolutely essential.

My question is this how bad is this in practice and why exactly? Is it reasonable to use it at all? Populating the components isn't really worth it as it would cost same as a new PSU. In that case I may just try my luck with a UK seller this time and hope for the best. I would appreciate some general thoughts and reasoning from someone with some experience with power supplies.
Jwillis:
Did buy that out of the back of a van? Just asking.
floobydust:
Sorry that looks like an elcheapo power supply. It may have been a decent design but every possible part stripped out to save pennies.
Missing fan control and short-circuit protection parts, and filter inductor L1 etc. Electrolytic capacitors C21, C22 are much smaller than the PCB footprint and some junky resistors there.

I would not invest much more time and money with it.
Brumby:

--- Quote from: floobydust on May 13, 2018, 12:18:59 am ---It may have been a decent design but every possible part stripped out to save pennies.

--- End quote ---

Including a very obviously missing heatsink.

Not getting any good vibes on this unit.
Eka:
There has been a problem with very low cost stripped down power supplies missing the safety circuitry they passed UL, CE and other safety standards with. More than a few fires have been caused by them.
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