recommendations for methods and circuit for Germanium transistor testing

[cooder]

I scored a bunch of ol skool Germanium transistors and wondering what methods and test circuits you guys would recommended for sorting through them. Looking obviously mostly for FF and Bender suitable sets in there.
Do you find R.G. Keen method like on Geofex site the way to go or other hints? TIA!
http://www.geofex.com/article_folders/ffselect.htm

[davent]

Small Bear also has an article but i can't remember which i built, probably the geofex, too many years...

http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm
davd

[mauman]

I finally broke down and bought a Peak Atlas DCA55, and it's now my go-to for transistor, diode and LED testing.  Costs about the same as a decent multimeter and worth it.  For Ge transistors, it will give you NPN/PNP, identify CBE leads, Hfe with test current used, Vbe with test current used, and leakage (critical for Ge transistors.)  Even tells you whether it's Ge or Si, based on the leakage, mine hasn't been wrong on that yet.  I use it to make up transistor sets for various boxes based on gain and leakage, and they usually sound right the first time.

[cooder]

Thanks for the hints guys!

I finally broke down and bought a Peak Atlas DCA55, and it's now my go-to for transistor, diode and LED testing.  Costs about the same as a decent multimeter and worth it.  For Ge transistors, it will give you NPN/PNP, identify CBE leads, Hfe with test current used, Vbe with test current used, and leakage (critical for Ge transistors.)  Even tells you whether it's Ge or Si, based on the leakage, mine hasn't been wrong on that yet.  I use it to make up transistor sets for various boxes based on gain and leakage, and they usually sound right the first time.

Anyone know how the cheapy ebay testers can work in comparison with the more expensive Atlas DCA55? Like this one here for example, any good experience with those?
https://www.ebay.com/itm/TC1-Transistor-Tester-ESR-Capacitance-Meter-Electronic-Component-NPN-PNP/233641565649?hash=item36661f5dd1:g:kRMAAOSwRvFfAwOg

[benny_profane]

A meter like that would be fine for Si parts and usually can identify pinouts alright. The lack of a know test current or ability to distinguish gain/leakage makes them unsuitable for Ge devices.

[cooder]

A meter like that would be fine for Si parts and usually can identify pinouts alright. The lack of a know test current or ability to distinguish gain/leakage makes them unsuitable for Ge devices.

Cheers I thought so. Might go with the Geofex and Smallbear methods, sounds more tried and true.

[Bret608]

Hi Stefan--I pretty much use the Geofex/Smallbear-type method. There's a vero layout for it over at tagboard effects. I just built one for NPN testing and one for PNP since it was so simple. However, the one thing that raised my game a bit was to get the testing spreadsheet that duhvoodooman posted at BYOC back in the day. It assumes you're using the Geofex tester, but you can just enter the actual resistor values used in your build rather than having to use trimmers or super-precise resistor values. Just copy the tab to create one for your PNP tester and one for NPN. Let me know if you have any trouble finding the spreadsheet. Trust me, this gets addictive quickly! Between doing your own testing and researching more deeply on what the classic circuits actually like, it's a rabbit hole.

[cooder]

Hi Stefan--I pretty much use the Geofex/Smallbear-type method. There's a vero layout for it over at tagboard effects. I just built one for NPN testing and one for PNP since it was so simple. However, the one thing that raised my game a bit was to get the testing spreadsheet that duhvoodooman posted at BYOC back in the day. It assumes you're using the Geofex tester, but you can just enter the actual resistor values used in your build rather than having to use trimmers or super-precise resistor values. Just copy the tab to create one for your PNP tester and one for NPN. Let me know if you have any trouble finding the spreadsheet. Trust me, this gets addictive quickly! Between doing your own testing and researching more deeply on what the classic circuits actually like, it's a rabbit hole.

Hi Bret! Thanks for the hints and the spreadsheet sounds awesome! If you have it handy and can post it here it would save me (and maybe someone else who watches this) some google foo. I haven't seen the original by duhvoodooman. Cheers!

[Bret608]

No problem! Here is the link to the relevant BYOC thread, which has the spreadsheet linked as well. Let me know if it helps.

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=38231&hilit=transistor+spreadsheet

[cooder]

No problem! Here is the link to the relevant BYOC thread, which has the spreadsheet linked as well. Let me know if it helps.

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=38231&hilit=transistor+spreadsheet

Awesome Bret, made my day! Have a good one!

[Bret608]

Glad to hear it! Let me know what your new stash reveals as you get into the testing. Don't worry if you find leaky ones--that's where the magic lies for Tonebenders.