Looking for a transistor tester

Kroars

Well-known member
I'm sure the tolerances are pretty lax. I'm planning to open it up and poke around.

Edit: Okay I almost never got the door OFF again, LOL. So, nothing to see inside really (smd components and a mega328p), but I found if you loosen the two bottom screws slightly, the battery door fits better (on this one).

As for batteries, I don't really use them often, but when I do I make sure they are as mojo as well. :cool:
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Not just mojo, but “Ultra” mojo!
 

StompBoxParts

Authorized Vendor
That's definitely good news to hear. Curious.... similar readings for hFE or Iceo and leakage (or both)? I was testing a few hundred transistors last week and the readings were not the same. In the ballpark, but definitely not the accuracy we wanted. That said, it was a terrible batch, almost all unacceptably leaky and we ended up rejecting the whole batch as less than 20% were useful and almost none in any of the "sweet spot" gain ranges.

I'm going to take a guess that if the device is lower leakage it will show up more accurately on a TC1 side by side with RG. If you got from a good source, they probably already sorted out the leaky ones. I'll look a bit closer with low vs high leakage in mind when we get a different batch of AC128s in (any day now!!!!).

16 hours and 400 transistors later (with more to go), I've come to a few conclusions comparing the TC1 and the RG Keen method side by side....

-The TC1 is a snapshot of measurements, which means it will NOT catch an instable or excessively leaky germanium transistor. You need to see this over time with a multimeter. If the leakage and hFE keep going up and up and up, it is bad. A good transistor will read nice and stable within ~1-30 seconds.
-The TC1 does not do a good job with low gain transistors regardless of leakage. In my test, the TC1 method were nowhere near accurate, always displaying a higher hFE.
-Once there's some gain ~70 and up, and the instable and very leaky transistors are weeded out, the TC1 does a pretty good job at displaying an accurate hFE and leakage/Iceo. Which means if you bought good transistors pre-sorted from a reputable place, the TC1 will give you fairly accurate results.
 
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fig

Village Idiot
Awesome information sir, thank you for sharing. I see the Kliche´ kit is now available in your store as well.

(oh and thanks for the heads up on the new stock of transistors)
 
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Big Monk

Well-known member
16 hours and 400 transistors later (with more to go), I've come to a few conclusions comparing the TC1 and the RG Keen method side by side....

-The TC1 is a snapshot of measurements, which means it will NOT catch an instable or excessively leaky germanium transistor. You need to see this over time with a multimeter. If the leakage and hFE keep going up and up and up, it is bad. A good transistor will read nice and stable within a few seconds.
-The TC1 does not do a good job with low gain transistors regardless of leakage. In my test, the TC1 method were nowhere near accurate, always displaying a higher hFE.
-Once there's some gain ~70 and up, and the instable and very leaky transistors are weeded out, the TC1 does a pretty good job at displaying an accurate hFE and leakage/Iceo. Which means if you bought good transistors pre-sorted from a reputable place, the TC1 will give you fairly accurate results.

I’m can’t pretend to test that many devices and my go to Ge device is the incredibly low leakage General Electric 2N169. Not the best data set from me!

Love the TC1 for Si, caps, resistors, etc. though.
 

fig

Village Idiot
I’m can’t pretend to test that many devices and my go to Ge device is the incredibly low leakage General Electric 2N169. Not the best data set from me!
Where are you getting 2N169s? Are those the pinch tops?
 

Big Monk

Well-known member
Where are you getting 2N169s? Are those the pinch tops?


SBE still has 125 in stock. These things are bang on between 60-120 hFE with very low leakage. I've only had a few over 70 microamps and I've had about 50 of them in my building career.

Edit: The gain bucket on this raw stock is typically even tighter than I quoted. I was factoring in some of the Fuzz Face and Tonebender MK II sets that Steve had cherry picked from this same lot. My last 4 hauls of 6-8 devices have all been between 70-110 hFE.
 
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fig

Village Idiot
Yeah, those are steady #s. I have a few in Steve's setups but I might get a few more.
I bought a group of MP21As and they are really consistent..(Iceo as well)

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Big Monk

Well-known member
I want Ge transistors that are leaky. I got ToneBender and FuzzTones to build...

Leakage is not your friend! Leakage is like an unpredictable chum at a keg party. You are never 100% sure how it will behave and it often requires a lot of supervision.

I'd rather tweak resistances on a low leakage unit and have stable bias then use a stock circuit with a wild card that may change on the whim of it's own electrons.
 
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Coda

Well-known member
Leakage is not your friend! Leakage is like an unpredictable chum at a keg party. You are never 100% sure how it will behave and it often requires a lot of supervision.

I'd rather tweak resistances on a low leakage unit and have stable bias then use a stock circuit with a wild card that may change on the whim of it's own electrons.
Unless you have a circuit designed for leaky transistors…
 

Big Monk

Well-known member
Unless you have a circuit designed for leaky transistors…

Healthy debate here.

Leaky transistors will cause bias to shift due to temperature but also simply playing them in a room temperature room. I've seen my bias drift even with low leakage transistors and a reasonable amount of playing time in my temperature controlled playing area.

In this day and age, and in my opinion of course, that's a design flaw. We can design that irregularity out of the equation yet still call upon it when we want.

Which does not detract from some of the design ingenuity of those old circuits. They used leakage to provide gating characteristics that eliminated, to a certain degree, the godawful noise issues in some of those fuzz circuits.

Short story long, leakage is not desirable. It's a flaw to be worked around. Yes, vintage circuits, in stock form, will bias correctly with leaky transistors. They will also exhibit major bias shift under even relatively normal circumstances. Variable and/or revised fixed bias resistors and low leakage transistors are much easier to get consistent results out of.

With that said, transistors also exhibit certain frequency characteristics between devices. So, sometimes the overall tone you desire comes from a leaky PNP transistors. It is what it is. I like the low leakage 2N169 but am moving mostly toward NOS Silicons because they seem to get me the tone I like over Germanium. I ordered a gang of old Silicon transistors from Small Bear in my last order.

Just my $0.02. Take that with a HUGE grain of salt!
 

peccary

Well-known member
I'm essentially a no-nothing when it comes to this stuff, but I think that I remember reading somewhere that the reason for using a germanium diode to bias a germanium transistor is that they can kind of self-bias with temperature changes. Is that a thing or am I just having a bad flashback?
 

BuddytheReow

Breadboard Baker
Sorry to revive such an old thread, but I've been looking into getting one of these to measure my J201 jfet values before socketing them. Have you used yours for that, and do you find it to work well for that purpose?
The TC-1 doesn't do well with Jfets. You need to measure Vgs for matching and this can't do it. You'll either need to upgrade to a better tester or get a jfet matcher doodad.
 

jwyles90

Active member
The TC-1 doesn't do well with Jfets. You need to measure Vgs for matching and this can't do it. You'll either need to upgrade to a better tester or get a jfet matcher doodad.
Thanks for the quick response! Any advice for finding said jfet matcher doodads? haha.

...Although after doing a quick google search it kind of seems like it would be easiest to just test the jfets once they're socketed in a specific build, and then find the ones that have the closest drain voltage?
 
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