There is a lot of 40 transistors marked as:
BC550
C K7A
(no logo)

I spent part of the morning matching them in pairs of similar Vbe for a constant current.They were all tested diode-connected (collector to base). No news here.

When trying to measure Ic for a constant Ib of 0,107 mA, found that no matter what Vb I applied to Rb (or leaving in the air), Ic was a steady 34 mA and transistor was rather warm.

After two hours checking everything, and contradicting what the datasheet shows, I reversed the pins (easy because base is the middle pin) and everything started to be "normal" with an Ic of 25 mA only when +9 V was applied to the base resistor. Otherwise, Ic = 0 mA.

Recalling that my DMM has hFE measurements, I got some credible value of 210 appr only when reversing the pins as above.

Further tests with a LED confirmed that something is going wrong: in the datasheet condtion, if I apply +9V to Rb and then leave it in the air, the LED stays dimly ON.

Reversing pins, LED switches ON and OFF as expected.

Last tests I did just for few of them. I had enough for he day.

Faked or failed ones sent to market expecting an idiot like me buying them?

 

I suspect that the pinouts may be different. Even transistors with the same part numbers can have different pin orders.

Eric

 

Hello,

As Eric stated the transistors may have a different pinout.
You could simply check it with a meter:
http://www.allaboutcircuits.com/vol_3/chpt_4/3.html

Bertus

 

I have one lot of faked PN2222 I bought a long while ago. It was still a good deal, the other 19 lots of different transistor (Qty 1000/lot) were good, and I paid a pittance for 20000 transistors. I suspect these were fall outs. Given the base price was something like $10 I didn't hold it against them.

BG Micro sells a lot of Mfg marked PN2222 for 1000/$4 if you are ever interested.

 

Gracias Bill and to all that replied.

It seems they had just the pins reversed because a detailed test show they are working OK.

After so many years of RTFM I trusted the 6 or 7 datasheets I looked for first. This time, it did not help and that is why I believed they were faulty (or faked).

BTW, those 4 USD, is a third of what I paid for the lot of 40 locally. Such is life...

Soldering now.