Cheap bench power supply tear-down (it's bad!)

Although I've been using this cheap MCH-K305D 30V, 5A 150W switching bench supply for quite a while, the current limiting has never worked so I figured I'd tear it down and take a look inside. It's *awful* - but what do you expect for US$60 I guess?

Stay tuned because eventually I will trace the fault and repair this unit.

[davidmaxwaterman]

> Stay tuned because eventually I will trace the fault and repair this unit

so....did you?

[horksog]

Its so refreshing to see Kiwis doing teardowns on youtube. Great content! Hello from Dunedin!

[FunkFPV]

I have a similar power supply and to adjust the current you need to short out the positive and negative.

[foder]

I'm not an Electrician or anything but i do find these Video's really interesting due to the Way Bruce explains things in way that regular folk can understand.

[Darryl]

Hi,
The green cap at 13:19 had zero solder on the right leg. .. Thanks for sharing.

[amtpdb]

I would like to see more track down and fix videos. DIY electronics for rc videos.
Thanks for taking the time to show us this.
Have a Merry Christmas and a better New Year.

[SAFbikes]

I really hope you soon make the video explaining your process of troubleshooting things like this. I'm learning so much from these teardown videos!

[helicrashpro]

One thing I have noticed with these cheap ebay power supplies (I have had a few of them) is that they say for instance 30V 5A which makes you thing it will put out 150W but they do not. They will usually only put out about 3-4V @ 5A which is only about 17W. BIG difference in output power. At 30V you will only get about 0.5A before it will start to limit the voltage. So what they mean is that they are 30V OR 5A at an unknown wattage. They can be useful for some things on a budget but don't trust the deceptive output.

[johnfrizza]

Fault-finding video - yes please! These tear-downs and technical exposés are great.

[PurityVendetta]

I have a 30v 10amp version of something like this but the inside is another world. I modded mine to quieten down a bit of switching noise and it's been great. I run it along a pair of tti dual, quad mode linear psus when I need the amps. Funnily enough the current control didn't work on mine but a quick look found one of the pins on the lead from the pot to the board had pushed out when it had been built. The board on mine is mounted top and bottom rigidly. Pretty well designed and functional for 40 UK quid.
You had me worried prodding around those caps 😊

[BenGovett]

Got myself a PS-305D which seems pretty solid. Same basic spec, but all forms of limiting work fine. Used both forms to my advantage all the time. Is more chunky like the second one you showed but I've never torn it down as it just works. Cost me around 80 AUD including local delivery. Worth every cent.

[onestevo]

Love to see how you track down the problem. Dave Jones style :)

[bongolongoallthetime]

You really don't know what you are talking about. An adjustable switching power supply is by no means trivial.
The build quality of the pcb is actually quite good for such a cheap device, all the IC seem to be made by premium manufacturers. The trim pots are multiturn variants which allows for repeatable adjustment.
The mechanical work is of course dodgy - but Wat do you expect from something as cheap as this?

[erwinscheringa]

Hi Bruce ! take a look at the legs of the green capacitor you filmed.. one of the legs isn't solderd at all..NIce tear-down !

[MkmeOrg]

13:02 I'd have a close look at C12- Looks like it might be missing some solder ;) I would just touch up all the through hole stuff as I can see some horrible ones and would only take a few mins to fix that up. Cheers

[KonstantinSbitnev]

Current limiting seems to work pretty well on mine. But you scared me, I feel I have to open it and look inside :)
Thanks! Looking forward to see it fixed.

[jonilarsen-haikarainen]

I keep expecting this guy to outburst "And Bob's your uncle!"

[oscarzt]

On your RCModelReviews channel, please may you explain why 'SimonK' ESCs have motor synchronisation problems and 'BLHeli' ones do not, and under what circumstances these problems do occur. Thank you.

[SKYFPV]

After watching one of your videos I went out and bought a Hakko 888D. Love it, thanks Bruce :o)

[snaprollinpitts]

hey Bruce, great video, I love to see what is going on inside. do more like this, I like it!!!