Germanium no leakage?

[Luke51411]

I just got a peak DCA55 and have been testing and labeling germs like a mad man  I have some that are in the 40-60hfe range that literally read 0 leakage current. I'm assuming it's just too low for it to read? I was of the understanding that all germanium trannys would have some leakage. I also found some high gain high leakage germs from around 150-250hfe and .5-.9ma of leakage. Are those going to be any good? I suppose I need to try them out in something to know for sure. What would be a good test bed for high gain germs?

[Electric Warrior]

You could try the high gainers in a MKII Tone Bender. Use the OC75 version schematic.



Leave away the 100Ω and increase the power filter cap's value to 50µF; it's the better way to fix squealing.

[Luke51411]

Thanks for the suggestion. I have a bunch more germs to test yet, probably around 100-200. I just got the dca55 and I'm enjoying it. After that I need to make some crazy fuzzes I think. Anything good to do with low gain NPN Germs? I have a bunch in the 40-60 hfe range with low leakage.

[Electric Warrior]

They should work fine for Q1/2 in a MKIII Tone Bender. For Q3 you'd want something with more leakage.

[smallbearelec]

Anything good to do with low gain NPN Germs?

They can be pure gold in Darlington pairs:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm
http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

NB: High-gain germanium has been used to good effect in Big Muffs.

[Luke51411]

Anything good to do with low gain NPN Germs?

They can be pure gold in Darlington pairs:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm
http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

NB: High-gain germanium has been used to good effect in Big Muffs.

Cool! I have a lot of candidates for darlingtons!

[mac]

150-250hfe and .5-.9ma of leakage

milliampere or microampere?

0.5ma, if milliampere, is not good for a FF, TB MKII, but ok for a TB MKI.

mac

[Electric Warrior]

The Peak gives out leakage readings in milliampere. 0.5 to 0.6ma is fine for a MKII and I believe some of my high gain OC75s leak even more than that (I'd measure, but it's incredibly hot in my room) and they still sound great in that circuit.

[PRR]

Germanium devices produced after ~~1969 "can" have low-low leakage.

The Silicon boys were really digging the fundamentals of semiconductor processing and learned a few things, which "leaked" (!) into late Germanium processing.

Ge always leaks more than Si, but it turned out that super-pure super-clean Ge doesn't leak as much as the junk we had been accepting 1950-1970. By that time "most" semiconductors fabs had gone all-Silicon. But there were a few pockets where Ge still had advantages. In the US, the low forward drop was valuable in BIG switching devices. And the low cost of Germanium was valuable both for those big devices, and for USSR and China's consumer markets (which did not get anything their military wanted).

Of course it could also be a mis-measure.

While handy-testers are good to have, you *should* know how to measure parameters without some smart/dumb microcomputer "helping" you.

Build R.G.'s circuit.
http://www.geofex.com/Article_Folders/ffselect.htm

For just leakage, you don't even need the pushbutton or the 2meg. The 9V and "2.472K"(!) are not fussy, 5V or 6V will do, 3K or 2K or even 1K will do.

Without the button, the transistor will leak Collector to Emitter. This current through the several-K resistor makes a voltage drop. If the drop is large, leakage seems to be large. If it is small, leakage is small.

The notes suggest that a couple Volts (2.472V) is "too much". A nice old-tech Ge part may show a tenth of that, or several tenths of a Volt. The very last Ge production may show 1/100ths of that, several dozen *milliVolts*, which may well be off-scale for the Peak. Si parts should be even lower, by a factor of 10 to 1,000 (a milliVolt to a few microVolts, your DMM can't read this).