Fake components?

[Boscoe]

Would you say these 2SC5200/2SA1943 are fake? I think they are...

[alex mm]

..... know the truth only with a hammer

[Andy5112405]

One way to test them is to build a little test rig and see if they survive at close to their expected SOAR.

[googlyone]

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)

[Tekko]

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.

[Andy5112405]

Originally Posted by Tekko

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.

The danger with this approach is that you will probably cause other damage to the amplifier.

[Andy5112405]

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.

[Tekko]

I have had output devices fail in my diy amplifiers, only needed to replace the outputs and the amp was alive again.

[effebi]

Originally Posted by Tekko

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.

[Tekko]

Well if a amp cant take that kinda brutality, its not a good or reliable amp to begin with.

Just my