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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 6th Apr 2019, 7:23 pm   #1
Steve G4WCS
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Default Chinese power transistors

Decided I'm going to build a high current power supply. I need a handful of 2N3055 or Tip3055 devices for the pass transistors.
I probably know the answer anyway but are the cheap chinese ones on ebay actually any good, or will they just prove to be 3 legged fuses/smoke generators ?

Also is it worth putting a wanted ad on here for these. I know I’d hoarded a few power transistors but just not enough of each type ?
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Old 6th Apr 2019, 7:30 pm   #2
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Default Re: Chinese power transistors

I wouldn't buy any semiconductors on ebay these days. Total minefield. It's not cultural at all as there's plenty of trash being sold here too. It's about supply chain management and qualification.

There's very little need to head in that direction anyway. If you look at CPC part number SC06752, which is an ST Microelectronics MJE3055T which is 50p a go in quantities of 1. Free delivery if you go above 8 ex VAT. You can get them even cheaper here if you fancy waiting a couple of weeks: https://www.taydaelectronics.com/mje...r-10a-60v.html

Cheap and made in China like all semiconductors. But the supply chain isn't rubbish.

Edit: one exception, I tend to buy lots of semiconductors usually SK type material where the parts were obviously purchased in the 60s-80s. Landed myself 200 2N4416's dated '69 in a lot for a fiver which I was happy about that way.
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Old 6th Apr 2019, 7:53 pm   #3
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Default Re: Chinese power transistors

Quote:
Originally Posted by Steve G4WCS View Post
Decided Im going to build high current power supply. I need a handful of 2N3055 or Tip3055 devices for the pass transistors.
I probably know the answer anyway but are the cheap chinese ones on ebay actually any good, or will they just prove to be 3 legged fuses/smoke generators ?

Also is it worth putting a wanted ad on here for these. I know I’d hoarded a few power transistors but just not enough of each type ?

You need to be careful. eBay is a broad church. There are reliable traders on there (Little Diode etc) but also junk vendors. I've found you can get good bargains from outfits selling off surplus stock, or new old stock from warehouse clearance. For the easily obtainable standard parts you are after though . I would agree with Mr. Bungle, buying from Farnell /CPC or RS is probably the way to go.
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Old 6th Apr 2019, 8:01 pm   #4
Steve G4WCS
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Default Re: Chinese power transistors

Hadn't even thought of looking at CPC, good shout, it's only up the road and I have an account, thanks
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Old 6th Apr 2019, 8:09 pm   #5
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Default Re: Chinese power transistors

Even better!
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Old 6th Apr 2019, 8:09 pm   #6
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Default Re: Chinese power transistors

yes its a lottery even branded types. used some in a 20 amp 13.8v kept going sc so tested ic. this was 2.4A before going sc not the 15A. replaced with nos
no problems they were from little diode Mick
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Old 6th Apr 2019, 8:37 pm   #7
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Default Re: Chinese power transistors

Would you like a few genuine Motorola MJ15024s?

Harvested from PSU heatsinks being scrapped at work. '80s vintage parts.

They're somewhat beefier than 2N3055s.
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Old 6th Apr 2019, 8:46 pm   #8
Steve G4WCS
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Default Re: Chinese power transistors

I'm certainly open to options and if they are on heatsinks even better, pm me with what you have please. Apart from the toroidal transformer it's going to be a parts bin special with a fluid design brief, thank you.
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Old 6th Apr 2019, 9:11 pm   #9
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Default Re: Chinese power transistors

Steve,
To show what you are up against in the wide market place the photo at the bottom of the first post in this thread is a fake. There is a huge amount of pictures on the web.

http://www.vintage-radio.net/forum/s...d.php?t=124222

As sugested above I might be inclined to pre test. Get a big heat sink and whilst keeping an eye on the temperature derating and safe operating area push up the current whilst watching the specs for saturation voltage as per the data sheet . ON Semiconductor quotes 1.1 Volts saturation at 400 mA base and Ic at 4Amp and 3.3Volts saturation at 10 Amp with 3.3 Amps base drive. But that is ON Semiconductor specs and I dont know the variation on other "Good" brands. But it should sort out the fakes as I doubt they would meet that test for long.
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Old 6th Apr 2019, 9:14 pm   #10
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Default Re: Chinese power transistors

Just saw the other posts - I am a slow typer. Better devices are a good choice to avoid the lottery.

Last edited by G4_Pete; 6th Apr 2019 at 9:20 pm.
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Old 7th Apr 2019, 9:12 am   #11
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Default Re: Chinese power transistors

I agree it's a bit of a lottery, particularly for 2N3055s for some reason.
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Old 7th Apr 2019, 9:33 am   #12
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Default Re: Chinese power transistors

2N3055 is a commonly-specified, general purpose NPN Silicon power transistor. It has a very easy specification to meet or exceed nowadays. If you make some NPN Silicon transistors that are good for at least 60V and 15A, but perhaps a bit less gain than you were hoping for, they nonetheless probably would substitute directly for a 2N3055 in many applications. So you don't need to waste them, you can sell them cheaply; and most of the time, the application won't be pushing the transistor anywhere near its limits anyway. It's only the most challenging applications where anything unusual shows up .....

I've also known modern 2N3055s with a much higher turnover frequency than the original part. These can be prone to bursting into ultrasonic or even RF oscillation, if the only precaution against this was the (reasonable, at the time of design) assumption that the transistor would have insufficient gain to sustain oscillation at such frequencies.
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Old 7th Apr 2019, 10:00 am   #13
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Default Re: Chinese power transistors

I think the moral of the story on 3055 oscillation is: don’t rely on the transistor being crap as part of your frequency compensation.
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Old 7th Apr 2019, 10:46 am   #14
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Default Re: Chinese power transistors

Quote:
Originally Posted by Steve G4WCS View Post
I'm certainly open to options and if they are on heatsinks even better, pm me with what you have please. Apart from the toroidal transformer it's going to be a parts bin special with a fluid design brief, thank you.
I've got a bag of about 80. They're loose devices, never soldered (the application used sockets) with a general smear of pigeon **** (heatsink paste) about them. Date code is 9540, the '80s ones I misremembered. (There was a production change around 1983 to devices with lower typical current gains). PM sent.
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Old 7th Apr 2019, 12:20 pm   #15
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Default Re: Chinese power transistors

Hi herald
Could i scrounge a few of those mj's if you've any to spare.
Greg.
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Old 7th Apr 2019, 2:55 pm   #16
Craig Sawyers
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Default Re: Chinese power transistors

It is not just eBay that sells Chinese stuff. Now there is a risk with that source that you will get fakes. But most semiconductors and batteries of whatever brand are now made in china.

Try looking at stuff on the Farnell website - they have a note at the end of each product that is the last country in which substantial manufacture took place - and the majority by far is China. RS use the two letter CN to denote that.

Apart from resistors, which seem to come mainly from India.

The west is becoming progressively de-skilled in the race to the product cost bottom.

Angry of Abingdon.

Craig
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Old 7th Apr 2019, 3:14 pm   #17
Craig Sawyers
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Default Re: Chinese power transistors

Thinking of fakes, about 9 months ago I bought 7 pairs of 2SC3264/2SA1295 power transistors on eBay. Before I soldered them in for a recent project, just to be sure I measured the size of the package using a micrometer, and it was outside the maximum tolerance for the Sanken MT200 package.

Now suspicious, I put one on the curve tracer (Tek 576) and compared it to a genuine part. It beta saturated at half the current of the genuine part, and had a Vceo of 125V as compared with 260V for a genuine Sanken part (spec 230V).

Weight was 14 grams as compared with 18.

So I used a hammer to expose the die.

The fake part had a die which was bonded directly to the heatsink plate, that was 2mm square.

The genuine part has an additional metal tab that doubles the thickness of metal under the 6mm square die. Hence the higher weight in the genuine part. The genuine Sanken part has a die with 9x the area of the fake.

I've contacted the seller (agiia) via eBay, twice, with evidence. He is not responding, but is still selling the fake power transistors.

Craig
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Old 7th Apr 2019, 3:43 pm   #18
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Default Re: Chinese power transistors

Choosing later, more advanced devices gives no real confidence.

Mr faker is sitting out there with piles of cheapo transistors of all sorts of packages. An order comes in for 25 off 2N123456789. He picks the right package and that is what he has his machine mark them as. Pack, ship, profit!

A friend who worked for a large semiconductor firm put out a request for a few off of a type number which had never existed to several suspect suppliers. It was on his firms web site (he put it there). He got some price quotes and he took them up. Devices with that marking and his firm's logo turned up. His firm forbade him going public in the trade press, they didn't want to frighten their customers.

Real manufacturers are aware of the problem and now their attitude is to be open about it and strongly advise the use of only authorised distributors.

David
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Old 7th Apr 2019, 5:58 pm   #19
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Default Re: Chinese power transistors

I'd be tempted to use modern devices specifically designed for parallel linear operation, have a look at the 2SC5200 for example, made with close vbe/gain characteristics for easy load sharing
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Old 7th Apr 2019, 11:15 pm   #20
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Default Re: Chinese power transistors

Hi,

If you are building a power supply intended for 2N3055's its often better to jump up to the 2N3773 (16A 140V). These, like the 3055, have been subject to cloning and many, even with vintage date codes and logos coming out the far east are not genuine old stock at all.

However, inside the USA there are companies that only hold old stock. If the moderators allow this link, this company (who sell products on ebay, consolidated electronics) have all genuine old stock, especially of Japanese transistors of which I have bought many from them. So if you went with these for your power supply, you could not go wrong:

https://www.ebay.com/itm/2N3773-Orig...8AAOSwAHBaFIbn
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