I Wonder about some of these CHEAP PARTS from Overseas, So.....

I Bought this Item, just because I needed some and was Curious about the REALLY CHEAP PRICE and FREE SHIPPING. (14.50 USD)
Received them Fairly Quick and they looked descent.

It just happened I had a request for one of my projects that required this IRF640, mainly for its higher voltage rating.
It is a Car Ignition Coil Driver that I have built Many Times, Never a Problem.
Uses 12 Volts and only about 3 or 4 Amps of Current, But some Voltage Spikes.
(And I do have a heat sink on it, just as an added precaution.)

Well it Lasted about 30 Seconds before going to a Complete Short.
I Replaced it with another one of these, Same Results.

Than I put in a IRF640, from my Present Stock and NO PROBLEM.
Runs Continuous for Hours on end.


50 x New IRF640 IRF 640N Power MOSFET 18A 200V TO-220 IR
Item ID: 280842386737
Return ID: 5022507193
Seller ID: jk_parts

They May be OK for Some Applications, But I'll stick to buying Quality Parts from Good Suppliers.
I Did complain and got a Full Refund, very quickly.

chemelec said:

jk_parts

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Looks like you got junk_parts .

If you want good parts then you should pay a fair price. There are too many cheaters "over there" who know that most gullible people will not bother asking for a refund.

Counterfeits are annoying, haven't occured to me yet but other junk from china, biggest was probably viribrights led-bulbs whose life-span was about 6 months, were about 17€/each.....what is funny, they were bought from TME, but it's not their fault, they can't test and be sure of all stuff they sell. At least I don't blame 'em. Maybe just got bad batch/bad luck but I don't buy those bulbs anymore. Each one had same problem; electrolytic cap inside was toast due overheat....
I would buy more from like farnell and other good brand-stores, but VAT and shipping are way too much to be paid...

This is only the Second time I bought any parts like this from Ebay.
The First time was some Step-Up Voltage Converter Modules and They do work good.

On these IRF640's, I Received a Full Refund the Same Day I Received them, and they don't want the parts back.
Just Glad I TESTED Them Right Away.
And when I get some free time, I will do some Testing on them to find out if they are Useful and Reliable for some other applications.

chemelec said:

and they don't want the parts back.

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Hehe, some stores in there are like: free shipping, but returns are not.
There are lot of good stuff in ebay, but then there's this stuff too. Ruins the fame of the place, sadly.
Good thing you got refund.

In my Complaint, I Offered to Return the Parts, IF they would pay the Return Shipping Cost.
But that would cost them almost as much as the Value of these parts.

It's obviously a crap shoot, but I've found that the sellers are quick to resolve issues when the parts are problems or even if they mess up shipments. They generally just accept it as the cost of doing business which they trade for not knowing anything about their own product and having obviously questionable parts. I buy a lot of modules and generally the only thing you need to worry about with those is the specs are inflated, but it's generally easy to tell what those specs actually are, just from the pictures.

I find for non-jelly bean parts the individual component prices are higher than digikey/mouser.

what does the "N" mean?
Sometimes it means a component that may fail the testing by a small amount.
Such as 78M05

The "N", has Nothing to do with Failure rates.

The "N", in the IRF640N, is for a Normal Package.
An IRF640NS is for a D-Pak
An IRF640NL is for a Low Profile Version.

chemelec said:

I Bought this Item, just because I needed some and was Curious about the REALLY CHEAP PRICE and FREE SHIPPING. (14.50 USD)
Received them Fairly Quick and they looked descent.

It just happened I had a request for one of my projects that required this IRF640, mainly for its higher voltage rating.
It is a Car Ignition Coil Driver that I have built Many Times, Never a Problem.
Uses 12 Volts and only about 3 or 4 Amps of Current, But some Voltage Spikes.
(And I do have a heat sink on it, just as an added precaution.)

Well it Lasted about 30 Seconds before going to a Complete Short.
I Replaced it with another one of these, Same Results.

Than I put in a IRF640, from my Present Stock and NO PROBLEM.
Runs Continuous for Hours on end.


50 x New IRF640 IRF 640N Power MOSFET 18A 200V TO-220 IR
Item ID: 280842386737
Return ID: 5022507193
Seller ID: jk_parts

They May be OK for Some Applications, But I'll stick to buying Quality Parts from Good Suppliers.
I Did complain and got a Full Refund, very quickly.

Click to expand...

Is this your problem?


Ratch

Yes I can see that happening on Electrolytic Caps.
But I think it is Less likely on Mosfets.

When I get back from my holiday in late part of February, I plan to do further testing on these Mosfets to determine if they have a Lower Current or Voltage Rating.
It is Possible they Re-Printed the IRF640 Part Number onto a Different, Lower Power Mosfet.

chemelec said:

Yes I can see that happening on Electrolytic Caps.
But I think it is Less likely on Mosfets.

When I get back from my holiday in late part of February, I plan to do further testing on these Mosfets to determine if they have a Lower Current or Voltage Rating.
It is Possible they Re-Printed the IRF640 Part Number onto a Different, Lower Power Mosfet.

Click to expand...

You might look at your circuit as well. A lot of parts are quite a bit better than there specs.. So you may have been skating by all these years.

The Circuit I am using is WELL UNDER the Requirements of this Mosfet.
It Should NEVER Fail in the circuit I am using.

Is the fender of the Chinese car made of rice-paper then it gets crumpled on a bicycle tire? I have never seen a Chinese car, I hope they never come to Canada.
Hopeless Russian Lada cars were here for a couple of years. Tiny little Smart cars are still here and I do not know why.

audioguru said:

Is the fender of the Chinese car made of rice-paper then it gets crumpled on a bicycle tire? I have never seen a Chinese car, I hope they never come to Canada.
Hopeless Russian Lada cars were here for a couple of years. Tiny little Smart cars are still here and I do not know why.

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Smart Cars are actually some of the safest on the road with a 5-star crash test rating. That's not to say you won't go for a ride if you get hit, but because of how it's built you will most likely not suffer any serious injuries. The driver sits inside of a "bubble" rollcage that protects them from impacts. Many people also don't know that Smart is owned by Mercedes Benz.

chemelec said:

They May be OK for Some Applications, But I'll stick to buying Quality Parts from Good Suppliers.

Click to expand...

I've learned to be cautious, also. I've bought a fair amount of Chinese electronic parts/devices, mostly through Amazon, and the majority have been OK; but enough have been defective that anymore, if I want something that is assured of meeting published specs I'll buy through Digi-Key instead.

I have bought a lot of cheap components on eBay from China & Hong Kong. I'd say about 15% of the time the parts are fine, another 75% work, but not quite exactly as per the data sheet and / or have been poorly manufactured in some way. The remaining 10% either don't work at all or fail very soon after installation.

So the bulk of the stuff ( 75% ) isn't quite up to par, but in many cases still useful, particularly in undemanding applications ( a lot of hobby circuits could be said to fall into that category ) However given that the majority ( 75% ) of the parts fall short in some way it is definitely NOT a good option whenever close spec or high reliability is called for

You get to learn which sellers sell good versions of certain parts with experience. With eBay there's always the option to return for a refund. With some potentially good, even great bargains to be had it can be a lottery worth playing.

audioguru said:

Is the fender of the Chinese car made of rice-paper then it gets crumpled on a bicycle tire? I have never seen a Chinese car, I hope they never come to Canada.
Hopeless Russian Lada cars were here for a couple of years. Tiny little Smart cars are still here and I do not know why.

Click to expand...

I often wondered why the Soviets chose to make the Lada cars ( one of their chief exports to the west ) to such a poor standard, was it a covert form of warfare! They were capable of building good stuff. I've bought quite a lot of Soviet surplus components on eBay and they've almost all been very well manufactured, so it seems bizarre that they would choose to showcase an inferior product to the outside world!

Another manufacturer of poor electrolytic capacitors is CapXon they are used in low cost consumer products and are frequently the cause of equipment failure.

I looked at this post: https://www.electro-tech-online.com/threads/buying-components-from-china.143706/
The question in that post was asked about component from China. The vast majority of replies said they are happy with what they bought.
In this thread the vast majority say that they have bad experience with Chinese components.
It looks like that what that matters is not what the question is, what that matters is who is asking.
I'll have to take your advice with a pinch of salt

Zahri, just to clarify my position. Although I stated that 75% of the parts I've bought fromChina fall short in some way, I would have to say that the vast majority say 85% of that 75% were perfectly acceptable and given the massively discounted prices represented good value for money.

From post #18 15% are perfect, from this post 85% of the 75% are very good, therefore 15% + 63.75% = 78.75%

More than 3/4 of all the Chinese components I've bought have been acceptable to me and have represented good value for money.