My Transistors, original or copy?

[sbrook]

One of the other problems in the "fake" market is the manufacture of "onspec" devices. A company goes to a manufacturer and asks them to do a run of say 100,000 unlabelled NPN and specify the simplest factors like VCE HFE and Dissipation.

Then they go and label them themselves with comparable type part numbers. Sometimes they're OK in the end user app. other times they're a disaster.

One of the clues with the "nonumber" parts is a different printing for the date code and the label. But you can't rely on that either, because a lot of transistors are similar and are manufactured from the same basic dies and are then selected and labelled according to the tests.

It's like buying in the "interchange" market. There are subtle differences between similar numbers, like BC182, BC183 and BC184 (BC107, 108 and 109) transisitors, but you'll often find them all under a single interchange number which for many applications, they are, but with different VCE and HFE and gain bandwidth products, you could come unglued.

[halfgaar]

Is it possible that there also are fake TO92 devices? I recently got a couple of 2sa1123 transistors, to replace a couple of noisy input-stage 2sa942 ones. I got about 8 or so in total. A few were dead on arrival, a few died after installing, and the ones that do work, have widely differing Hfe values.

These are the original and the replacement:

[anatech]

Hi halfgaar,
The new transistor is okay for a sub, but I would have used 2SA872 instead.

With a wide gain spread and high failure rate, I would say those are either copies or factory rejects.

-Chris

[sbrook]

2sa1123 is manufactured by Panasonic (Matsushita) and has the standoff blips on the leads and a factory lead offset like the 2SA942 you took out. Your 2SA1123 has neither. I'd say it is a fake since it appears that it doesn't even meet the specs.

Moreover, Panasonic has superceded the A1123 with the A1123S

[halfgaar]

2sa1123 is manufactured by Panasonic (Matsushita) and has the standoff blips on the leads

What exactly are standoff blips?

and a factory lead offset like the 2SA942 you took out

Like so?:



edit: I assume the 2SA872 also has an offset middle pin?

Moreover, Panasonic has superceded the A1123 with the A1123S

Since when is this?

[sbrook]

Not quite ...

Look at your A942 ...

The outer two legs bend outwards and then down. That's actually done in the transistor production and not during assembly into a board. This appears to be standard on Matsushita (Panasonic) TO92 case transistors.

Then also as you come out of the bottom of the A942, the legs get fatter and then thinner again (blips). This is so that the transistor cannot seat all the way down on the board when inserted into a PCB (It "stands off" the PCB)

See here ... http://www.ortodoxism.ro/datasheets/...JC00011BED.pdf

[anatech]

Hi sbrook,
Lead forming occurs when components are supplied taped. Bulk transistors are typically straight with no bends. Component insertion machines need the bends done before they ram the part into the PCB. Just because the leads are not formed does not mean they are fakes.

I use offset pliers to form the leads into that shape.

The 2SA872 matches the specs of your 2SA942 more closely.

-Chris

[halfgaar]

Lead forming occurs when components are supplied taped. Bulk transistors are typically straight with no bends. Component insertion machines need the bends done before they ram the part into the PCB. Just because the leads are not formed does not mean they are fakes.

What about the standoff blips?

[anatech]

Hi halfgaar,

What about the standoff blips?

That's just a crimp. Special order I suspect. It's the same thing, parts supplied on tape for automatic insertion. Bulk parts are supplied with straight leads generally.

[Eva]

Originally posted by halfgaar
Is it possible that there also are fake TO92 devices? I recently got a couple of 2sa1123 transistors, to replace a couple of noisy input-stage 2sa942 ones. I got about 8 or so in total. A few were dead on arrival, a few died after installing, and the ones that do work, have widely differing Hfe values.

These are the original and the replacement:

I think that TO-92 devices have by far the largest fake market, although the quality sometimes is not as deceiving as with high power devices.

If some devices were faulty on arrival, you should return all them, get your money back and try another source. According to what you tell, all seem to be fakes (unless you managed to damage them in some unexpected way).