One way to test them is to build a little test rig and see if they survive at close to their expected SOAR.
Can't say for the pictures you show.
I have been had on two occasions in the past (both times buying off ebay). As noted above, there are two ways you can gain confidence:
-1- Build a test jig and drive the devices at a good fraction of their rated current. At the same time test the DC Hfe as you wind up the current. This tests bonding and die current limits, and allows you to plot the DC Hfe as a function of collector current. You should find the HFe is very similar to that published for them (usually greater Hfe).
I found that one batch of fake devices firstly has low Hfe, and secondly failed at a small fraction of their rated current.
I also found that some of the fake devices had NO die in them at all - have a photo somewhere - I was laughing so hard when I found that I almost forgot what I paid for them.
As part of this crank up the voltage such that the devices are operating somewhere near max dissipation at a fair VCE. Obviously you will need a heatsink etc. Remember to keep the device inside it's SOA, but don't be shy to really test it.
If the above are OK, then I suggest you are OK.
If you are worried, and especially if a device fails:
-2- Crack a couple of samples open.
Most of the fake devices I had used very small dies. I also cracked open a "known good device" to compare. (seems stupid, but I really wanted to know what I was looking at)
I have been had on two occasions in the past (both times buying off ebay). As noted above, there are two ways you can gain confidence:
-1- Build a test jig and drive the devices at a good fraction of their rated current. At the same time test the DC Hfe as you wind up the current. This tests bonding and die current limits, and allows you to plot the DC Hfe as a function of collector current. You should find the HFe is very similar to that published for them (usually greater Hfe).
I found that one batch of fake devices firstly has low Hfe, and secondly failed at a small fraction of their rated current.
I also found that some of the fake devices had NO die in them at all - have a photo somewhere - I was laughing so hard when I found that I almost forgot what I paid for them.
As part of this crank up the voltage such that the devices are operating somewhere near max dissipation at a fair VCE. Obviously you will need a heatsink etc. Remember to keep the device inside it's SOA, but don't be shy to really test it.
If the above are OK, then I suggest you are OK.
If you are worried, and especially if a device fails:
-2- Crack a couple of samples open.
Most of the fake devices I had used very small dies. I also cracked open a "known good device" to compare. (seems stupid, but I really wanted to know what I was looking at)
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Or do it my way: Take a homemade amplifier, install devices in question, then give the amp hell and see if they survive.
That is use a inefficint speaker like a 4 ohm high power car subwoofer driver and turn the amp right up to clipping, if it survives this treatment, the devices are likely genuine.
When i got hit with fakes, i was unable to get the amp to work at all, either it just kept sticking to either rail, ignored the Vbe multiplier and drawing 5 Amps or it just failed instantly on power on.
That is use a inefficint speaker like a 4 ohm high power car subwoofer driver and turn the amp right up to clipping, if it survives this treatment, the devices are likely genuine.
When i got hit with fakes, i was unable to get the amp to work at all, either it just kept sticking to either rail, ignored the Vbe multiplier and drawing 5 Amps or it just failed instantly on power on.
The danger with this approach is that you will probably cause other damage to the amplifier.
As a lot of fake transistors use inferior dies. Try the Vce test.
From the datasheet of the suspect device ascertain the Vce(max).
With a reasonable resistor (say 1K) in series connect just below this Vce across the Collector / Emitter with nothing connected to the Base.
An inferior die may fail causing current to flow through the device. A good transistor will survive with no current flowing.
If that works measure Hfe.
If Vce and Hfe seem OK then the device is probably genuine.
From the datasheet of the suspect device ascertain the Vce(max).
With a reasonable resistor (say 1K) in series connect just below this Vce across the Collector / Emitter with nothing connected to the Base.
An inferior die may fail causing current to flow through the device. A good transistor will survive with no current flowing.
If that works measure Hfe.
If Vce and Hfe seem OK then the device is probably genuine.
I have had output devices fail in my diy amplifiers, only needed to replace the outputs and the amp was alive again.
Well, I am quite sure the drivers are not happy....
and emitter resistors as well. Many times I have seen them damaged on power amps with shorted OPs.
I will not recomend this brutality in any amplifier that I care of.
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Well if a amp cant take that kinda brutality, its not a good or reliable amp to begin with.
Just my
Just my
Yeah, sure.Well if a amp cant take that kinda brutality, its not a good or reliable amp to begin with.
Just my
Good for you, but , again I will STRONGLY NOT recomend to do so to anybody else, in all my honesty, and for the good technical sake of this forum.
Not all the amplifiers around are good and robust like yours, I guess, but not for that reason they deserve to be brutalized in that way.
Nothing of personal,
effebi
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Running at high current with sufficient base current to just saturate ON is another good test that does not dissipate enormous power. This will find small high voltage die
That's what I also think. They look real to me unless they are super-fakes which I doubt. The markings are a little bit different but that's OK. They are probably manufactured in 2 different Toshiba's factories. As far as I know, there is a factory in Japan and an authentic Toshiba's factory in Thailand. 🙂 Here is a simple circuit for testing 2SC5200/2SA1943. There is an adapted version for 220V mains as well. Try it. 🙂
Transistores falsificados
Just test the base-emitter capacitance and see if it's around 7 nF. If it's fake it will be less than half that.
If you get them through regular distribution channels, the chances of a fake are less than 5%. On E-bay, about 95%.
Yours actually *look* good to me, but I test samples from every batch from distributors, and every single device from surplus outlets.
Yours actually *look* good to me, but I test samples from every batch from distributors, and every single device from surplus outlets.
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This is becoming a bigger and bigger problem! Even authorized distribution channels are seeing an increase in fake components and some estimate up to 20-25% fakes/recycled components are circulating the market. The audio industry is particularly hit b/c some 'audiphile' credibility makes for inflated prices.
So when you get a deal on a batch of Sanken transistors, Allen Bradley carbon comps, or nice electrolytics, they may very well be fakes.
The problem is so big that some economies depend on this black market that it may never be fixed. The original producers do not bother taking up the fight, which makes me suspect some rather large economies are invloved. Can we, the buyers, do something? Does it matter?
So when you get a deal on a batch of Sanken transistors, Allen Bradley carbon comps, or nice electrolytics, they may very well be fakes.
The problem is so big that some economies depend on this black market that it may never be fixed. The original producers do not bother taking up the fight, which makes me suspect some rather large economies are invloved. Can we, the buyers, do something? Does it matter?
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