Ge transistor testing unusually high - Hfe over 500??

[Brossman]

Hey y'all,

Been a long time since I dove into electronics projects. Been busy with my MS thesis, but I'm back at evaluating stock so I can clear clutter. So naturally I got sidetracked in testing Ge transistors! As you do...

I was testing old TI 2n130x devices and tried the single 2n1309 I found in the bin. The test rig is basically like Steve's simplified version with 9.00v (from a regulated benchtop supply) and a 1Mohm resistance (set by a decade I built into my Ge test box) to get 9uA of Base current.

I read around 400uA of leakage, but it was still going down about 2uA per second after a couple minutes. After throwing the switch to see the standard conduction, levels jumps to 4.5mA (YES, mA) and continued to climb at a rate of about .05mA per second. After reaching nearly 6mA, I turned it off as it looked like some sort of runaway... nonetheless a quick calc shows that as Hfe ~600. Holy crap, y'all!

I thought I'd try it at 5.00v instead, and that gives me around 1550uA total -  166uA leakage, and 5uA of base current to yield Hfe = 277... at 5v??

Is there something wrong with this transistor? ...Cuz it seem like a badass little hotrod!

[smallbearelec]

After reaching nearly 6mA, I turned it off as it looked like some sort of runaway.

Some devices will "self-heat" in this way even with no added Base bias. Others will go into that mode when bias is added. Either way, I would not recommend using such devices in a pedal--too unstable.

[Brossman]

Okay, thanks Steve! What an interesting problem... I'll put it in a bin of rejects. I keep some bad parts so I know how to test for them.