"Runaway" collector current with AC176

[chromesphere]

Hi all,
Found something interesting today.  I got 10 AC176's.  3 of which are quite leaky and very high gain (150-250).  The other 7 read very high collector current, 4ma, one registering 10ma!  The thing is, that it climbs upwards.  And keeps going. Probably until it will burn out. I assume this is a build up of heat.  It seems odd that a component would be manufactured at such a high failure rate (7/10).  Was i sent duds (ebay)?  I have noticed other people have had difficulty with these transistors.  Are the 7 with 'runaway' current issues pretty much useless, bar, using them as ge diodes?
Cheers!
Paul

[bancika]

I stopped caring for AC*** transistors because they are so f'ing unreliable. I bought half of dozen of each ac125 and ac128. All the 128s had perfect gains around 120, but leakage of 1000uA! All the 125s had gains around 15 (data sheet says 50+). Total garbage.
Out of curiosity, which store did you get them from? May be the same

[Kesh]

http://en.wikipedia.org/wiki/Thermal_runaway#Bipolar_junction_transistors_.28BJTs.29

[Chugs]

Were they from Minifux on ebay?

[chromesphere]

Were they from Minifux on ebay?

Bingo!

Minifux1.  I wonder if this guys siphoning off all the good ones and selling the cr@p?  I did get some good ones in the ac128 group.  Under 300ua and 100-120hfe and 60-80 hfes.  But i also got, maybe 50% that were off the chart.

7 of 10 ac176's were throw aways....im so suprised that a company could manufacturer a component that is so ridiculously unreliable...either that or as i said above, dodgy seller.  He's got a tonne of unsealed transistors.  Its a bit suspicious...

Paul

[chromesphere]

All the 125s had gains around 15 (data sheet says 50+).

I may have the answer to this...
ive learnt a bit about the ac125 range in the last few days.  There are different revisions or batches.  For instance AC125 V is hfe 50-100.  VI is hfe 75-150.  Etc.  You gotta watch which roman numeral follows after the product code "ac125".

Doesnt explain the 15hfe? Well...Did you buy ac125z perhaps?  I absolutely combed through every god dam page on the internet to try and find what that z suffix represents.  The answer is that its a high voltage version of the ac125.  If you look at the short form datasheet of the ac125z compared to the ac125, you will see the collector current used in the test conditions is higher.  So maybe (assuming you bought the ac125z's) they measure low hfe in stompbox applications? 
I had the same problem with the GT308B's that were claimed 50-160 or whatever it was.  Most only measured 40-80.  The problem again being, the gain doesnt hit 90-160 until you increase the collector current to 20ma or something high like that...

Anyway, I've ordered some of these so we'll soon see i guess.  I got a feeling i just ordered a metric crap-tonne of useless transistors (AC125z's). The joys of Ge transistors!

Paul

[bancika]

Were they from Minifux on ebay?

Bingo!

Me too 

[chromesphere]

Were they from Minifux on ebay?

Bingo!

Me too 

Well...either the ac176 is an absolutely terrible, poorly made to the point of uselessness, transistor or this guys skimmed them

Paul

[LucifersTrip]

or it was a bad batch...or it was stored in poor conditions...or