Cheap Chinese Electronics.

[orbiter]

OK the story goes like this..

Today I decided to try out my new eBay purchase, which is basically a hard drive USB converter/adaptor kit. It allows me to connect SATA or IDE hard drives simply via a USB port which is very convenient for swapping data around between various drives. Even before I ordered this thing I understood that the purchase was not going to be for a top quality item, but rather a cheapo China brand unit, and so I also understood that quality control and testing of this adaptor may not have been up to much. However I assumed that these things must have to be tested to some degree, so I got one & thought hey.. It’s only a 12v adaptor, what can possibly go wrong.

One week later I needed to find some data on a few older IDE drives that I had, so I plugged in my new toy and all was great, it worked a treat. I could connect all my drives without having to take the sides off of my main computer, and transferring data was breeze. After around 10 minutes use though I noticed that the little PSU for the adaptor kit was running pretty hot, (not just warm either. Hot!) Around 10 more minutes passed and I was still happily transferring data, when from behind me came a pretty loud BANG!! (Well it sounded  pretty loud as my room is quite quiet) I turned around to find blue smoke filling the air along with a really bad burning electronics smell. Jeez I crapped myself (gladly not literally ? )

The damn cheapo PSU which feeds the hard drives had exploded inside its casing like a small bomb, the LED had gone off and there were now bits rattling around inside the casing. Anyway I was just glad that the thing didn’t actually blow the case apart as there’s a chance it could have set our house on fire

So.. on to the evidence… 








I have contacted the eBay seller and he was apologetic and promised to send me another PSU, he did mention that the PSU could have been damaged in transit, although I don’t think so as it was packed very well indeed and this unit has obviously suffered component failure.
 
To be honest, I can see longevity being a problem generally with these things as they run too hot. The hot part I was feeling originally was the transistor heat sink which was resting against the plastic case. Now I’m no engineer but the heat sink doesn’t look big enough to me, and certainly doesn’t do its job efficiently enough to keep the transistor at a reasonable operating temperature.

By the way.. What is the exploded component guys, Is it a fuse of some sort?
 

orbiter

[Simon]

hm looks like a germanium diode (typically made of glass) but I can't understand why one would be used in a SMPS or any power supply for that matter. judging by the burn on the board it was more than just that part that failed

[orbiter]

hm looks like a germanium diode (typically made of glass) but I can't understand why one would be used in a SMPS or any power supply for that matter. judging by the burn on the board it was more than just that part that failed

Yea understood. The only other thing I can see though is the blown out piece of trace and the broken soldered joint. The thing blew up as if it was wired up the wrong way on the 240v side, but it wasn't.

[jahonen]

I also thought about germanium diode, but I guess that is some kind of PCB fuse. At least the reference designator on the PCB says "F1". It also looks like that bit of a PCB trace is vaporized, probably the switching transistor closed permanently.

High running temperature is quite sure sign of short-life expectancy. I have personally evidenced destruction of two Chinese 12V 1A SMPS, first failed on high temperature (but fortunately didn't blow up), second failed on un-plugging after long use, and then it wouldn't work anymore probably due to bad capacitors. Then I gave up and made my own from 24 VAC output wall-pluggable conventional transformer (only type that has no components what can go mysteriously bad) and quick-and dirty LM2675 based switch-mode regulator on a veroboard which makes steady 12 volts from rectified and filtered 24 VAC. That has worked ok so far.

Regards,
Janne

[lhc]

It's a fuse:
http://www.made-in-china.com/showroom/lsd822/product-detailGoOnHiCDfukF/China-Glass-Tube-Fuses-0-5A-30A-.html

[mikeselectricstuff]

That's the most pathetic fuse I've ever seen!
I have a dissection of another dodgy psu on my site.

[Simon]

holy crap, a fuse ? that was the logical solution but that's the dodgiest fuse I've ever seen

[orbiter]

I'll get a shot of the top of the board for you guys to see. Gimme a minute .

Here ya go fellas...

I bent the cap out of the way as it was stuffed up right by the power transistor but you can just see the there is another transistor underneath the cap.



It seems the large transistor was the culprit. This is purely due to either a faulty transistor or I believe more likely insuficient cooling? I'll take it out and have a look underneath.

[Kiriakos-GR]

I have an similar USB converter SATA or IDE .

Never had an issue ..

[orbiter]

Yea that's the same thing Kiriakos-GR, however your PSU is a different model to mine so hoepfully yours is a good one.

[PetrosA]

One thing I can say for sure is that the heat sink should be through-bolted and not screwed on with a sheet metal screw

[Simon]

what is the brown stuff on the heat sink ? looks like cap juice, with those temperatures the cap will not last long

[orbiter]

what is the brown stuff on the heat sink ? looks like cap juice, with those temperatures the cap will not last long

That's what I thought when I first saw it my friend, however it seems that it was that rubberised stuff they spray on to keep components from vibrating around.

[Kiriakos-GR]

The positive part are that even so ,
the fuse inside did the job , and nothing extreme happened.

We all own lots of those PSU's , for our laptops , chargers , networking stuff , you name it ..

Personally I had only one incident, with an similar PSU that came with my 3COM Wifi bridge .

One resistor was touching the insulation of one electrolytic capacitor ,
the resistor heat up ( normal effect ) , but the heat melted the insulation of the capacitor,
and  they shorted together , I got the familiar " bang " noise .  

I opened it up , replaced the resistor with new , and I rearrange the parts, so to have an safe clearance.

I was lucky , the problem was at the end of the DC output, so I had few troubles as repair .    
If the damage was at the pulsing part , I would probably send it for recycling .  

[orbiter]

Yes It will probably end up in the bin, or I may modify the circuit somehow for my own training needs (I know I need it.) However I won't be using the 240v side.

[Kiriakos-GR]

Hey , post a picture of the PSU label , its good to know how it looks like,
so to be avoided from the many ..

[orbiter]

Hey , post a picture of the PSU label , its good to know how it looks like,
so to be avoided from the many ..

The best I can do my friend is the model number, I ripped the label to bits looking for any screws that may have been holding the case together

Anyway..

AC-DC Adaptor Number is.. YH-3028 and it comes with the R-Driver USB 2.0 to SATA IDE Cable kit.

Hopefully the new adaptor I get as a replacement will be a better one, however I'm not holding out much hope. If I recieve the same type (and it's as hot as the last one) I will be taking it apart and rebuilding it with a more suitable heatsink.

orbiter

[Simon]

put some holes in the case for ventilation

[orbiter]

put some holes in the case for ventilation

I'll probably do that Simon, Thanks.

I think if the new one runs as hot as the old one though I may need a little fan on top of it too, although that's not a problem as I've got loads of those lying around from various computer rebuilds

I'll keep this thread up to date with my little story as the new PSU should be here in a day or two.

John

[Kiriakos-GR]

put some holes in the case for ventilation

I did it , but its an bad idea ... as safety concern ..

This devices are not repairable, thats why they are sealed airtight .

I did it , but I told to my self , that this PSU will never operate at one not moderated spot.

The next time that something will go wrong , it can drive flames out of the box , and start an true fire,
in a carpet or curtains .

 

[saturation]

I buy quite a number of various no name cheap Chinese ac-ac or ac-dc power supplies, often as low as $1 each, includes shipping.  I've posted about this elsewhere.

I make sure the cases are screwed in, so I can disassemble it easily and it will look OK once reassembled.

I open them all to examine the construction and design.

I have found flaws in 75% of them, but all easy to fix, added soldering here, insulation here, cleaning there.   However, if you get a substandard part that potentially can cause a fire, examination won't tell until you use it.

When I run PSU I do so nearly all through a fused or circuit breaker enabled power strip, so the power strip is the first to take the brunt of the failure.  I also do a burn in on the test bench, to insure it won't be a hazard when lying on the floor, behind furniture, and start a fire.

[Mechatrommer]

thats normal, nothing to worry about.

[orbiter]

OK, just the keep the thread up to date.. I got my new PSU today and gladly this one seems much cooler. It's a different model number too (GX34W-5-12.)
I took a temp reading from the hottest part of this unit and compared it against the faulty one, and found that this one runs around 20*C cooler which should assist with it's furure health and temptation to explode

John