Counterfeit 2SC5171 ?

[sandyK]

I have posted this here, because the 2SC5171 and 2SA1930 is so widely used in many projects posted here.

Has anybody encountered counterfeit Toshiba 2SA1930 or 2SC5171 ? A friend of mine made the following comments to me in a recent email (edited) :

Just spent a while matching up my pile of 2SC5171’s & 2SA1930’s. Worryingly, the one batch, which may have been the last lot of ‘5171’s were way down on Hfe. They have a different finish & markings, although they appear genuine and xxxxxxxx (U.K.) have been pretty good so far. For info, my average Hfe is around 196 on the 5171’s but on this batch they are only between 40 & 85! (The ‘1930’s are all around 200 – 220)
The Toshiba datasheet states HFE of 100 to 320 at .1A
Their graph is almost ruler flat from <1mA to well past 100mA, so this shouldn't be due to the particular transistor tester used ?
SandyK

[homemodder]

Could be chinese second source, they produce most toshiba devices real rubbish, get a refund. Wingling or something like that they are called.

[dantzig65]

I also got me a bunch of 2SC5171 with Hfe around 40. Threw then away...

[gain]

first double check your measurement equipment (i know obvious advice but sometimes we all forget, at least i do). measure a known good transistor and verify high hfe. then measure one from the suspect batch and note low hfe. do this at least a couple times to verify test instrument is working correctly.

if ok, construct a simple test circuit that will run suspect device near the edge of its SOA. not outside the SOA, just close. push 'er a little. but put a fuse in the rail(s) !!!! let this run a few days and see if tansistor goes poof or survives.

or just call and complain to customer service and see if they will send you a new batch if you send back the old? but its not unusual ime for power transistors to very wildly in hfe.

[gain]

just to clarify for those reading is the purpose of the test circuit i mentioned is that often fake transistors will fail pretty rapidly when run close to their SOA, even for short periods of time. the real mcCoy on the other hand, while it may get warm, will handle this situation like a champ for days on end.

[sandyK]

The attached diagram was compiled by D.Mitchell from Rock Grotto Forum.

[gain]

does yours look like the top or bottom? if bottom email customer service with this image as well as a photo of the transistor(s) they sent you and demand a refund.

[sandyK]

gain

The major U.K. company involved did replace the inferior transistors, and were very helpful. I understand this lot was sourced from a different distributor to normal.
The replacement transistors wer genuine Toshiba as shown at the top, and their HFEs were all in the vicinity of 200.

SandyK

[gain]

so your problem is solved then, great!

[jaycee]

SandyK, mind if i ask which company? As they have done The Right Thing I see no harm in naming them, but if you don't wish to do so publically, private message me.