Transistors - faked or failed ones?

[atferrari]

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 mater 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?

 

[harold777]

Faulty components are to be found in any sphere of commerce. That you seems to have found (from what I understand) a large number of similarly marked transistors, may point to a rogue seller, OR more likely a bulk purchase that was rather "too cheap" - but without a proper branding it is difficult to lay blame anywhere along the supply chain.
Be gratefulk you spotted this situation before they were soldered into expensive boards and sent to customers...

Perhaps we have got used to 100% good components?

 

[Mr RB]

In the old days BC series commonly came with a few different pinouts. It was a real pain. You probably just have a different pinout to what you were expecting.

 

[atferrari]

In the old days BC series commonly came with a few different pinouts. It was a real pain. You probably just have a different pinout to what you were expecting.

You are right. I always RTFM (6 or 7 this time, all coincident in the pinout) thus my confusion with faulty or faked ones.

This morning I tested them considering valid the "new" pinout and everything is in order.

Thanks to you both for replying.

Now soldering and happy.

 

[alec_t]

Another posssibility: some device pin-outs are pictured 'from the top' whereas others are 'from below'. Not all datasheets make the viewing direction obvious.

 

[ericgibbs]

hi at,
This diagram is useful transistor pin outs.

E.

 

[ghostman11]

hi at,
This diagram is useful transistor pin outs.

E.

Eric you have the nack of coming up with some great links! alot of my most useful folder has come from you