Saturday, January 28, 2017

[Random Teardowns] YU4802 48V/2A power supply

Device: Cheap 48V 2A power supply (YU4802)
Origin: Aliexpress
Reason for teardown: Preemptive checkup
Impressions: Not bad for the price ($14 shipped)

Blue Power LED on top

Yeah, but if I don't it's still a risk due to being a 96W  $14 power supply from china so.... bring on the risk of electric.

Noname primary-side cap, mismatched screws on the TO-220s but the design doesn't seem to be too terrible at least
Based on UC3842 (datasheet)

3 noname secondary side caps, par for the course

I've seen way worse for the same amount of money.
So after actually using this with a significant load (charging a 50cell 10S5P LiIon battery) I can say that it's really not a very efficient power supply and that it should probably never have been designed into this enclosure. A hundred vent holes and a fan later I'm now reasonably sure it won't burn down.

This is a very similar circuit to what they sell as SLA battery chargers for electric bicycles in cases 4 times this size with vent slots all around. Even so they get stupidly hot and just cook the transformer if the vents are covered up as a friend of mine found out. Primary side shorts straight through leaving nothing intact.
So if you buy this and want to use it anywhere near it's rating then break it apart, get your drill out and turn the case into swiss cheese at the very least but I'd recommend active cooling as well in addition.


  1. hmm... the marking on the bottom of the pcb is PNYU..
    pronounced "pwn you"? just sayin'

  2. I bought one of these and I got a half supply (about 129VAC) electric shock from touching the plug negative and an earthed device....!

    If I earth the Negative output it trips the earth leakage breaker every time... So it's a piece of crap don't buy it...!

  3. sorry, what is the resistance value of the resistor R10?


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