# Using TC-1 tester to measure ge transistors -question



## Kroars (Feb 29, 2020)

Hope everyone is well.  I’m building a War Scythe and at the point of matching 2N1308’s.  I’ve got a handful of them and am hoping to use this tester to match a pair.  Knowing that hfe is gain, what are the other four measurements shown in the photo? More importantly which one (if any) is leakage?


Hfe (gain) = 136
Ube (?) = 145mV
Ic (?) = 1.5mA
Iceo (?) = 78uA

Thank you in advance!!


----------



## tcpoint (Feb 29, 2020)

Leakage isn't shown in those 4 measurements.  If your meter doesn't take leakage into account then your hfe will be off.

Note: Iceo shows leakage.  I didn't read the post carefully.  See my correction, later.


----------



## Kroars (Feb 29, 2020)

Thanks for the response! Could you tell me what the measurements (aside from hfe being gain) stand for?


----------



## tcpoint (Feb 29, 2020)

Guess I lied.  Iceo is the current leakage at the emitter.  Anything under 100 is good.  You're hfe.isn't super high but should high enough for a muff.  It would work well for Q2 in fuzz face.  Ube is the dx voltage between the base and emitter.  Usually, .65 in silicon and between .15 and .3  (this from memory so it's probably a little off) in germaniums.  Ic is the current used for the test at the collector.  Sorry about the first post.


----------



## Kroars (Feb 29, 2020)

tcpoint said:


> Guess I lied.  Iceo is the current leakage at the emitter.  Anything under 100 is good.  You're hfe.isn't super high but should high enough for a muff.  It would work well for Q2 in fuzz face.  Ube is the dx voltage between the base and emitter.  Usually, .65 in silicon and between .15 and .3  (this from memory so it's probably a little off) in germaniums.  Ic is the current used for the test at the collector.  Sorry about the first post.





tcpoint said:


> Guess I lied.  Iceo is the current leakage at the emitter.  Anything under 100 is good.  You're hfe.isn't super high but should high enough for a muff.  It would work well for Q2 in fuzz face.  Ube is the dx voltage between the base and emitter.  Usually, .65 in silicon and between .15 and .3  (this from memory so it's probably a little off) in germaniums.  Ic is the current used for the test at the collector.  Sorry about the first post.



Thank you kindly! I’ve got about 20-30 ac176 and 2n1308 I scored from Russia.  It was actually a pretty good batch, only a couple were a low hfe.  Most AC176 were above 100hfe and 2N1308’s were in the 200-400 even a couple at 600 hfe.  Just used this one for the photo example.


----------



## Chuck D. Bones (Mar 1, 2020)

Iceo is collector-to-emitter current with the base lead not connected to anything. It is an extreme case because in most circuits, the base has a DC path to somewhere.  Some testers also measure Ices, which the the collector-to-emitter current with the base lead shorted to the emitter.  The leakage current in-circuit is somewhere in between Iceo & Ices.
Ic is the collector current used for the HFE measurement and maybe the Vbe measurement too.  Most pedals run the transistors at Ic under 1mA, some, like the Harmonic Percolator, below 100uA.  Some testers measure HFE at 5mA or higher, which is not particularly useful to pedal builders.
I have yet to see any Ge transistors with HFE over 300.  Not saying they can't exist, I just find 600 very hard to believe.  More likely your tester is making a measurement error.
When measuring Ge transistors, you have to let them sit in the tester for a few minutes so they can cool off after being heated by your fingers.  Only then will you get a stable reading.
There is nothing to be gained by "matching" the transistors in a Big Muff.  They all work independently, unlike the transistors in a Fuzz Face.


----------



## Kroars (Mar 1, 2020)

Chuck D. Bones said:


> Iceo is collector-to-emitter current with the base lead not connected to anything. It is an extreme case because in most circuits, the base has a DC path to somewhere.  Some testers also measure Ices, which the the collector-to-emitter current with the base lead shorted to the emitter.  The leakage current in-circuit is somewhere in between Iceo & Ices.
> Ic is the collector current used for the HFE measurement and maybe the Vbe measurement too.  Most pedals run the transistors at Ic under 1mA, some, like the Harmonic Percolator, below 100uA.  Some testers measure HFE at 5mA or higher, which is not particularly useful to pedal builders.
> I have yet to see any Ge transistors with HFE over 300.  Not saying they can't exist, I just find 600 very hard to believe.  More likely your tester is making a measurement error.
> When measuring Ge transistors, you have to let them sit in the tester for a few minutes so they can cool off after being heated by your fingers.  Only then will you get a stable reading.
> There is nothing to be gained by "matching" the transistors in a Big Muff.  They all work independently, unlike the transistors in a Fuzz Face.


Thanks for the detailed response.  Very much appreciate the answer!


----------

