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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 8th Apr 2019, 10:16 am   #21
Steve G4WCS
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Default Re: Chinese power transistors

Quote:
Originally Posted by G4_Pete View Post
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.
Pete
Funnily enough, Its the BNOS 12/25 circuit I was thinking of using as a basis for my power supply
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Old 8th Apr 2019, 4:09 pm   #22
tri-comp
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Default Re: Chinese power transistors

Some times it's not so difficult to spot the fakes off eBay.
These 2N3055's were still wet behind the ears when I received them.
Recently I bought a mix of small zener-diodes off eBay and the other day I needed a 39Vz for repairing a LAB-amp.
In the bag labelled 39V were 10 Zeners and only ONE of them came anywhere near to 39V at 38,6V. The rest were below 36V.
Now, would YOU trust the single Zener within range to do repairs to a LAB-2000C amplifier ? In my country they sell at +500 used.

/Torben
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Old 8th Apr 2019, 4:55 pm   #23
G6Tanuki
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Default Re: Chinese power transistors

It's not only popular audio transistors that are victims of fakery; the problem extends into RF power-transistors too: several 1980s Motorola "MRF"- and International Rectifier "IRF" devices as used in CB sets, ham transceivers etc are now more often fakes than not, likewise the 'integrated power-amp' blocks produced by Mitsubishi and used in old VHF/UHF commercial two-way gear.

There's no easy answer to this: paying a lot and buying from reputable mainstream dealers is no guarantee that fraud hasn't taken place somewhere in the supply-chain. At least the likes of CPC, RS etc. are going to be easier to get a refund from if the deal does turn out to be a bad one.
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Old 8th Apr 2019, 6:12 pm   #24
G4_Pete
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Default Re: Chinese power transistors

Steve,
If you do adopt the BNOS 12/25 as a design basis add in a soft start as many of these old designs were conceived in the wire fuse era and will trip modern domestic breakers on inrush.
Pete
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Old 8th Apr 2019, 8:23 pm   #25
Steve G4WCS
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Default Re: Chinese power transistors

Scary just how much fakery is out there . And good shout Pete Ill add a soft start
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Old 11th Apr 2019, 9:46 am   #26
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Default Re: Chinese power transistors

I got a pack of 2N3055 from ebay for fun and they tested with a HFE range from 30 to 100( 20-70 for a good one )
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