# Looking for a transistor tester



## BuddytheReow (Oct 8, 2021)

Finally got my small bear order in and need to measure pinout, hre , and leakage.  I've got npn and pnp for both silicon and geraniums. Is there a cheapo one from Amazon you guys can recommend? Thanks


----------



## Coda (Oct 8, 2021)

I just ordered this one. Won’t be here till Monday, but someone else around here has one…

https://www.amazon.com/gp/aw/d/B091281YKX?ref=ppx_pt2_mob_b_prod_image


----------



## fig (Oct 8, 2021)

Coda said:


> I just ordered this one. Won’t be here till Monday, but someone else around here has one…
> 
> https://www.amazon.com/gp/aw/d/B091281YKX?ref=ppx_pt2_mob_b_prod_image


Will that measure germanium leakage?


----------



## fig (Oct 8, 2021)

This is Mr. Keen's DIY test method...

If you have a batch of germanium transistors, how do you tell which are going to sound good and which will not?  To a first order, you can just gain select them in a DMM that has a transistor checking range. However, all modern DMM's assume that the transistor being testing has no leakage at all. They just put a metered amount of base current in and look for how much collector current comes out. With germanium's inherently higher leakage, this just makes a leaky device look like a higher gain device. 




This is one way to sift the leakage from true gain. You hook up a couple of resistors and a DMM to the device, and the resistors set up conditions you can control to see what is what. If you really want to do this, get a 2.2M resistor and a 2.4K ; better, get one each 2.2M and 2.49K metal film 1% resistors. This will set you back about US$0.30 if you get them from Mouser, and slightly more or less than that from other sources. If you're going to do much of this, get a transistor socket to, so you can easily test a large number of devices.

If you are satisfied with an indication of gain but are willing to settle for lower accuracy, you can carbon film at 5%, but recognize that the accuracy will be less. If you can, get several 2.4K resistors and measure them. You may find one that's closer to 2.472 ohms, which would be ideal. I'm being picky about the ohms because if you get exactly 2.2M and 2472 ohms, and use a 9.0V battery,  you'll find that the voltage across the resistor will be numerically equal to the indicated gain! That's why the somewhat odd resistor values, and the discussion on the values. It makes the final numbers on your DMM come out about right - multiply the voltage by 100, and that's the gain.

To do the test, stick the transistor in the socket, and read the DC voltage across the 2.4K resistor. The resistor will convert any leakage current from the transistor into a voltage that you can then read on your meter. A 2472 ohm resistor is 2.472 volts per milliamp, so a milliamp of leakage will cause 2.472 volts to display. That is incredibly too much leakage, so any transistor that does that is not going to be useful for a FF. In fact, although it will differ a bit, any transistor that shows more than a few micro amps of leakage is suspect. Because of the resistor scaling, the indicated value on your meter is "false leakage gain" and will have to be subtracted from the total reading that you do next.

To test the total gain, press the switch that connects the 2.2M resistor to the base. This causes a touch more than 4 microamps of base current to flow in the base. The transistor multiplies this by its internal gain, and the sum of the leakage (which doesn't change with base current) and the amplified base current. If the transistor has a gain of 100 and no leakage, the voltage across the 2.4K resistor is then (4uA)*(100)*(2472) =  0.9888V - which is almost exactly 1/ 100 of the actual gain. Pretty neat, huh? 

But we know that germanium really does have leakage - that's why were doing this little dance in the first place. So, let's say that the device leaks 100uA to start with. We stick the device into the socket, and read the voltage before we press the switch. It reads (100E-6)*(2472) = 247mV. So the leakage is making the meter believe that there's a "gain" of almost 25 with no current into the base at all.

How much leakage is too much? 100uA is common, 200 happens pretty often. More than 300uA means the device is suspicious, and more than 500uA I would say is bad.

Let's say the device really leaks 93uA, and has a gain of 110 - a prime specimen. What happens when we test? We chuck the thing in the socket, and read (93uA)*(2472) = .229V. Then we press the switch, and read 1.330V. To get the real gain, we subtract 0.229V from 1.330V and get 1.101V. The true gain is just 100 times the reading. 

Hey! How come it's 110.1, and not 110? Well, that's from this being an imperfect world, and from this tester being built with some approximations. The exact base current is 4.046...uA, assuming that the transistor's base conducts that much with a forward voltage of 0.1V (reasonable with germanium at these currents) and that the battery is *exactly* 9.0000V, and that the resistors are 2.20000M, and...   well, you get the picture. 0.5% accuracy is doggone fine for work with such blunt tools, and much better than you actually need to make a fine sounding FF. Besides - if you're clever, you'll flip the switch and watch the voltage while you  put your finger on the transistor. Simple finger heat will make the gain rise rapidly. What's the real gain? All of them are - at the temperature and conditions of the moment.


----------



## Big Monk (Oct 8, 2021)

This is what I use:



			https://www.amazon.com/Pocketable-Multifunctional-Backlight-Transistor-Capacitor/dp/B07X5YS1JN/ref=asc_df_B07X5YS1JN/?tag=hyprod-20&linkCode=df0&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092&psc=1&tag=&ref=&adgrpid=93604202533&hvpone=&hvptwo=&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092


----------



## fig (Oct 8, 2021)

Both of those are good. Stomp Box Parts carries a similar one for $25.


----------



## bowanderror (Oct 8, 2021)

Big Monk said:


> This is what I use:
> 
> 
> 
> https://www.amazon.com/Pocketable-Multifunctional-Backlight-Transistor-Capacitor/dp/B07X5YS1JN/ref=asc_df_B07X5YS1JN/?tag=hyprod-20&linkCode=df0&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092&psc=1&tag=&ref=&adgrpid=93604202533&hvpone=&hvptwo=&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092


I use the same one. Decent enough for Ge transistors, here is how I interpret the measurements:

*Germanium Transistors:*

*hFE* - _DC_ _Gain_ - hFE = Gain parameter measured under DC conditions
*Vbe* - _Voltage b/w Base & Emitter_ - (mV) - 0.65-0.7V for Si, 0.15 to 0.3V for Ge.
*Ic* - _Collector Current used for test_ - (mA) - Most pedal transistors run Ic <1mA. Some (i.e. Harmonic Percolator) run below 100uA. Some testers measure hFE at 5mA or higher, which is not particularly useful to pedal builders.
*Iceo* - _Leakage Current at the Emitter _- (mA) - Collector-to-Emitter current w/Base lead not connected to anything (an extreme case as in most circuits, the Base has a DC path to somewhere) - Anything <100uA is good
*Ices* - _Collector-to-Emitter current with the Base lead shorted to the Emitter_ - (uA) - Leakage Current in-circuit is somewhere in between Iceo & Ices.
So not always the best for leakage, but it will give you a good idea of the comparative values between individual transistors.


----------



## Coda (Oct 8, 2021)

fig said:


> Will that measure germanium leakage?


I’ll let you know on Monday.


----------



## Big Monk (Oct 8, 2021)

bowanderror said:


> I use the same one. Decent enough for Ge transistors, here is how I interpret the measurements:
> 
> *Germanium Transistors:*
> 
> ...



I compared the TC1 to the R.G. Method enough times to stop the R.G. Method altogether. 

It’s close enough and easier.


----------



## bowanderror (Oct 8, 2021)

How do the TC-1 Iceo & Ices measurements compare to R.G.'s leakage values?


----------



## Big Monk (Oct 8, 2021)

bowanderror said:


> How do the TC-1 Iceo & Ices measurements compare to R.G.'s leakage values?



Iceo is pretty much dead on. Close enough at least to not have to worry about it. +/- 20 microamps is not a deal breaker.


----------



## fig (Oct 9, 2021)

I ordered a TC-1 and a Mega328.

I'll do a shootout between the Keen method, the DCAPro, and the other two above. I'll post my results in the Test Kitchen (seems appropriate).


----------



## SillyOctpuss (Oct 9, 2021)

Big Monk said:


> This is what I use:
> 
> 
> 
> https://www.amazon.com/Pocketable-Multifunctional-Backlight-Transistor-Capacitor/dp/B07X5YS1JN/ref=asc_df_B07X5YS1JN/?tag=hyprod-20&linkCode=df0&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092&psc=1&tag=&ref=&adgrpid=93604202533&hvpone=&hvptwo=&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092



I honestly have the worst luck with these.  I've had two of the model above and neither of them lasted more than four weeks.  Both of them turned off during a test and just didn't turn on again. 

I also had a TC7? I think that was the model number and the screen died on it.  You could still just about see the text so it must have been the backlight. 

I was going to buy a Peak Atlas but don't really have the cash at the minute and I need to test some transistors for a build this weekend.  I thought I'd try one more and this guy turned up about 20 mins ago





I have a few issues so it's going back to Amazon tomorrow.  Problem A - the battery cover won't fit over a 9v battery.  As you can see below the battery sits higher than the shelf the flat cover slides over. 





Problem B -  The blue adaptor to connect the components was in the battery cover when it arrived.  It just slides into some holes below it.  Whenever you put a part in to test you have to hold the other side or it just lifts up when you lock a part in place






I know these are cheap but this one feels especialls pants

On the plus side it does seem to be pretty accurate.


----------



## Coda (Oct 9, 2021)

SillyOctpuss said:


> I honestly have the worst luck with these.  I've had two of the model above and neither of them lasted more than four weeks.  Both of them turned off during a test and just didn't turn on again.
> 
> I also had a TC7? I think that was the model number and the screen died on it.  You could still just about see the text so it must have been the backlight.
> 
> ...


Does it measure leakage?


----------



## SillyOctpuss (Oct 9, 2021)

I don't know.  I've only tested some Bc549 and ba282 diodes.  I'm about to put my kid to bed then I'll check and let you know.  

It should do, the other two models I had measured leakage and they all use the same basic software.


----------



## finebyfine (Oct 9, 2021)

Coda said:


> Does it measure leakage?



I have this one, and if it does I don't know how to. It's also bad at recognizing JFETS. It sucks that there isn't something $35 as good as the DCA75 but it was a worthwhile purchase for me personally. I use the one pictured to check caps and resistors though and it's great for that and easier than a multimeter for me.


----------



## SillyOctpuss (Oct 9, 2021)

Wow so this one wont measure leakage like the TC1 and T7 will.  I just tried to test some ASX12D PNP transistors and it only gives the same data as the screenshot I posted above.  Pinout, HFE and Vf.  Sorry @Coda but if you want to measure leakage you'll need one of the others.  Can you cancel your delivery? I'm requesting a return label for mine now and will send it back tomorrow.


----------



## BuddytheReow (Oct 9, 2021)

Based on what I’m reading here and elsewhere there isn’t a Swiss Army knife type of tester under $35. I may just get a basic one and use the Geofex method of measuring leakage and just call it a day


----------



## manfesto (Oct 9, 2021)

I have a Mega328 (you can buy them prebuilt or as a kit, with or without a case, depending on how much you want to spend). It does hfe, Iceo and Ices, and it’s been *so* handy for testing batches of germaniums I’ve been getting from eBay to suss the good ones from the duds.

@Chuck D. Bones was the one who recommended it, which is basically the highest praise one can give a product ‘round these parts right?

This is the exact listing I bought but anything “GM328” is gonna be the same thing








						GM328 IC-TTL Transistor Tester with Clear Case - Component Tester  | eBay
					

Find many great new & used options and get the best deals for GM328 IC-TTL Transistor Tester with Clear Case - Component Tester at the best online prices at eBay! Free shipping for many products!



					www.ebay.com


----------



## Big Monk (Oct 9, 2021)

BuddytheReow said:


> Based on what I’m reading here and elsewhere there isn’t a Swiss Army knife type of tester under $35. I may just get a basic one and use the Geofex method of measuring leakage and just call it a day



The TC1 is about as good as it gets in that price range. I’ve yet to find something it doesn’t do.

It compares very favorably to the R.G. Method and is light years simpler and there is no math involved.


----------



## mdc (Oct 11, 2021)

I have the DCA55 and I’d say it was worth the splurge.


----------



## bowanderror (Oct 11, 2021)

mdc said:


> I have the DCA55 and I’d say it was worth the splurge.


As someone who has killed many a cheapo tester, the sturdier & more accurate DCA55 is worth the money if you're looking for a long-term solution. I only wish it could also measure JFET Vp & Idss, as that would make it the standout option over cheaper testers. Unfortunately, only the DCA75 does that, and it's $130 vs. $60 for the DCA55


----------



## Big Monk (Oct 11, 2021)

bowanderror said:


> As someone who has killed many a cheapo tester, the sturdier & more accurate DCA55 is worth the money if you're looking for a long-term solution. I only wish it could also measure JFET Vp & Idss, as that would make it the standout option over cheaper testers. Unfortunately, only the DCA75 does that, and it's $130 vs. $60 for the DCA55



I contemplated getting a DCA75 when I was making my Aion Ares, but since I only use JFETs sparingly, it's more economical to just whip up a JFET tester on the breadboard when I need it.


----------



## bowanderror (Oct 11, 2021)

Big Monk said:


> I contemplated getting a DCA75 when I was making my Aion Ares, but since I only use JFETs sparingly, it's more economical to just whip up a JFET tester on the breadboard when I need it.


I do the same with a veroboard matcher and it works great! To more easily compare JFETs for matching, you can also calculate Rds(on) from:

*Rds(on)* = -Vp/(2*Idss)  -  I use the terms pinchoff voltage (Vp) and Vgs(off) interchangeably here

I usually bulk test my JFETs and add them to a spreadsheet to calculate that & identify matching pairs:


----------



## danfrank (Oct 11, 2021)

Hi!
I made myself a RG Special and carefully selected the two resistors like RG notes in his article. No math is involved, you just have to move the decimal over 1 place to get actual values.
I even use this tester for silicon transistors, which 99.9% of them show zero leakage, but the tester works great for silicon BJTs also.
I even installed a charge pump in the box and a 9 volt regulator so a battery going south won't affect the results.
Highly recommended and a super easy build!


----------



## Big Monk (Oct 11, 2021)

danfrank said:


> Hi!
> I made myself a RG Special and carefully selected the two resistors like RG notes in his article. No math is involved, you just have to move the decimal over 1 place to get actual values.
> I even use this tester for silicon transistors, which 99.9% of them show zero leakage, but the tester works great for silicon BJTs also.
> I even installed a charge pump in the box and a 9 volt regulator so a battery going south won't affect the results.
> Highly recommended and a super easy build!



If the TC1 tester was not so cheap and accurate, I'd agree with you!


----------



## fig (Oct 11, 2021)

For FET matching, I use this;

<a href="https://oshpark.com/shared_projects/tG4sSkqf"><img src="https://oshpark.com/packs/media/images/badge-5f4e3bf4bf68f72ff88bd92e0089e9cf.png" alt="Order from OSH Park"></img></a>

btw, the test unit from Amazon arrived today. I realized I had no 9v batteries about and was about to use the PSU when I wondered..._would a draining battery affect the test results?_ Above my pay grade unless I can demonstrate it empirically (or one of you clue me in.

The TC-1 is on it's way and I'll compare them both to the DCAPro. I'm considering doing as Dan and including Mr. Keen's test rig. I'll try to share the results in some meaningful fashion. I am certainly open to advice or tips........there's a jar over yonder.


----------



## fig (Oct 16, 2021)

I ran some comparisons between the TC1 which was purchased at StompBoxParts for $25, and the TaoBao (atmega328) purchased from Amazon for $21.69. I used the Peak DCAPro and Peak LCR45 for reference purposes only. This is not to say that the Peak devices are or are not more accurate. Seems the funding for this project was held up by those bastard bureaucrats (no offense Hermes) at the University of Mars in preparation for "_Elon's arrival". _Those ninnies were always suckers for celebs. Where was I? Oh yes, alone and flying blind!







Not the most scientific approach perhaps but it should give the reader at least _some_ idea of what they get for their $

I tested a variety of components and all 3 devices were pretty close, with the exception the DCAPro measured higher gains on Ge transistors. The other two were very close to one another. I'll look into this further, as this can be a pretty critical measurement in some circuits and I personally would like to know if the DCAPro could be misreporting these.

Testing Ge transistor leakage is not available on the TaoBao from Amazon.

The clamp assembly on the TC1 is flush mounted and permanently attached, whereas the TaoBao must be inserted into what looks like a 4x7-hole breadboard, which is not stable and really defeats the purpose of having a clamp. I found it easier to leave the clamp assembly off and shove the component into the breadboard.

The TC1 has a rechargeable battery and comes with a USB charging cable. The TaoBao requires a 9v transistor battery.

The TC! also came with 3 mini-grabber test leads.


















In like, my opinion man, The TC1 is a clear winner for an additional $3.31


----------



## StompBoxParts (Oct 16, 2021)

We're big fans of the TC1! We have them all around the Cusack campus, great little tester for all sorts of things and super simple to use. 

As discussed, it is not the perfect tester for germanium transistors. It will get you in the hFE ballpark (reporting higher from leakage). We'll sometimes use it as a second opinion or if we need to do a rapid test of a bunch of germanium. We use RG Keen's method as our primary test for sorting.


----------



## SillyOctpuss (Oct 16, 2021)

Did the battery cover fit on TaoBao after a battery is inserted in your unit @fig?


----------



## fig (Oct 16, 2021)

I didn't have one handy, so I used my bench supply. I meant to test that too! Hang on..


----------



## Coda (Oct 16, 2021)

SillyOctpuss said:


> Did the battery cover fit on TaoBao after a battery is inserted in your unit @fig?


It fit on mine. I’m upgrading to  the TC-1, though. However, the TaeBao has been working pretty well…just no leakage.


----------



## Big Monk (Oct 16, 2021)

StompBoxParts said:


> We're big fans of the TC1! We have them all around the Cusack campus, great little tester for all sorts of things and super simple to use.
> 
> As discussed, it is not the perfect tester for germanium transistors. It will get you in the hFE ballpark (reporting higher from leakage). We'll sometimes use it as a second opinion or if we need to do a rapid test of a bunch of germanium. We use RG Keen's method as our primary test for sorting.



This is interesting to me as my personal tests, with a TC1 and breadboarded RG tester side by side, show striking parity between the two in almost every device I’ve ever tested.


----------



## SillyOctpuss (Oct 16, 2021)

Coda said:


> It fit on mine. I’m upgrading to  the TC-1, though. However, the TaeBao has been working pretty well…just no leakage.


I wonder if the one I had was a little thinner.  There's no way a 9v was going to fit.  I can't measure now though as I've already sent it back.


----------



## fig (Oct 16, 2021)

Nope. Will not go on.


----------



## fig (Oct 16, 2021)

Wait...I got it on there! Sheesh. I had to force the little tab down to do it!


----------



## SillyOctpuss (Oct 16, 2021)

fig said:


> Wait...I got it on there! Sheesh. I had to force the little tab down to do it!


I kinda wish I still had mine here to measure the depth.  There's no way a 9v was going to fit in the one I had.


----------



## fig (Oct 16, 2021)

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. ​


----------



## StompBoxParts (Oct 16, 2021)

Big Monk said:


> This is interesting to me as my personal tests, with a TC1 and breadboarded RG tester side by side, show striking parity between the two in almost every device I’ve ever tested.


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!!!!).


----------



## Kroars (Oct 18, 2021)

fig said:


> Will that measure germanium leakage?


Not accurately (or perhaps hit/miss is a better descriptor). It’s great for quick measurements of caps, resistors and silicon transistors.  I’ve got this one and the TC-1, they’re almost identical.  The TC-1 turns on and tests a bit faster but they’re both great for what they do.  I think the DCA55/75 is about the only thing that measures GE transistors anything near accurately aside from long form with a DMM.


----------



## Kroars (Oct 18, 2021)

fig said:


> 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. ​


Not just mojo, but “Ultra” mojo!


----------



## StompBoxParts (Nov 10, 2021)

StompBoxParts said:


> 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.


----------



## fig (Nov 10, 2021)

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)


----------



## Big Monk (Nov 15, 2021)

StompBoxParts said:


> 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 (Nov 16, 2021)

Big Monk said:


> 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 (Nov 16, 2021)

fig said:


> Where are you getting 2N169s? Are those the pinch tops?











						NPN Flat-Hat Raw Stock
					

Small Bear Electronics DIY Parts




					smallbear-electronics.mybigcommerce.com
				




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.


----------



## fig (Nov 16, 2021)

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)


----------



## Coda (Nov 16, 2021)

I want Ge transistors that are leaky. I got ToneBender and FuzzTones to build...


----------



## Big Monk (Nov 16, 2021)

Coda said:


> 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.


----------



## peccary (Nov 16, 2021)

Big Monk said:


> Leakage is not your friend! Leakage is like an unpredictable friend at a keg party.


What's a kegger without an unpredictable friend or twelve?


----------



## Big Monk (Nov 16, 2021)

peccary said:


> What's a kegger without an unpredictable friend or twelve?



Just remember to not turn up the heat or else your leaky transistors will go streaking through the Quad...


----------



## Coda (Nov 16, 2021)

Big Monk said:


> 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 (Nov 16, 2021)

Coda said:


> 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!


----------



## fig (Nov 16, 2021)

Major Fuzzkill.


----------



## Big Monk (Nov 16, 2021)

fig said:


> Major Fuzzkill.



What can I say? I’m a modernist!


----------



## peccary (Nov 16, 2021)

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?


----------



## jwyles90 (Mar 16, 2022)

Big Monk said:


> This is what I use:
> 
> 
> 
> https://www.amazon.com/Pocketable-Multifunctional-Backlight-Transistor-Capacitor/dp/B07X5YS1JN/ref=asc_df_B07X5YS1JN/?tag=hyprod-20&linkCode=df0&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092&psc=1&tag=&ref=&adgrpid=93604202533&hvpone=&hvptwo=&hvadid=416638923984&hvpos=&hvnetw=g&hvrand=12121426703188084439&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9005070&hvtargid=pla-845729973092


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?


----------



## BuddytheReow (Mar 16, 2022)

jwyles90 said:


> 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 (Mar 16, 2022)

BuddytheReow said:


> 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?


----------



## BuddytheReow (Mar 16, 2022)

It's pretty much a DIY project.

Here's RG Keen's method. You can find a stripboard layout out there.


			http://geofex.com/Article_Folders/fetmatch/fetmatch.htm
		


If you're looking for a PCB





						OSH Park ~
					






					oshpark.com
				





			https://rullywow.com/wp-content/uploads/2014/05/JFET-matcher-rullywow.com-Build-Doc-v1.01.pdf


----------



## Phil hodson (Mar 17, 2022)

I just built one of these Rully boards. Not yet used it but I ordered a couple of extras. I think I have three left. If anyone want one Pm me. Happy to help out. 
They are just the PCB (unpopulated)


----------



## Bricksnbeatles (May 20, 2022)

I’ve got the Taobao, and aside from the ZIF socket being kinda pointless with how it wiggles around, it seems to be fine for what it is.

 I was just testing some diodes today and noticed that if you measure a diode in test pins 1 and 2 or 1 and 3 it gives an “Ir” reading in addition to the Uf (forward voltage). I previously always tested diodes in pins 2 and 3 of the socket (just by chance, not a deliberate effort) and it only gives you the  forward voltage and the capacitance of the diode in that case. 

As I is of course current (derived from the German word for current I think) I’m assuming Ir of a diode is reverse current or something to that effect. It’s been quite a while since I took an EE class, so I can’t remember if that’s a common measurement or what purpose it serves to know— Google was of little help. 

As the Ir tends to be around 2nA for most diodes, and that’s 2/1,000,000 mA, it seems to be pretty insignificant, but some diodes were as much as 0.2mA so I’m curious what these readings signify and what applications they may be taken into consideration in. Paging Dr. @Chuck D. Bones to the Tool Box!


----------



## benny_profane (May 20, 2022)

Ir is the reverse current. When a diode is reverse biased with a voltage not in excess of the breakdown voltage, a small amount of current is able to flow. So, even though this is the ‘off’ state, there’s a non-zero current. Check out the I-V curve of a diode’s data sheet. In the reverse side, you’ll see a small jump from the voltage axis (x). That small bump is the Ir reading you’re seeing. As reverse voltage approaches the breakdown voltage (Vbr), the current begins to increase until it is essentially an open circuit.

EDIT: The following graph is taken from the onsemi 1n914 data sheet:





Silicon diodes are typically in the nA range you cited. Germanium devices can exhibit quite a bit higher Ir values.

This phenomenon is what is talked about with 'leakage' and is exhibited with transistors as well.


----------



## Bricksnbeatles (May 20, 2022)

benny_profane said:


> Ir is the reverse current. When a diode is reverse biased with a voltage not in excess of the breakdown voltage, a small amount of current is able to flow. So, even though this is the ‘off’ state, there’s a non-zero current. Check out the I-V curve of a diode’s data sheet. In the reverse side, you’ll see a small jump from the voltage axis (x). That small bump is the Ir reading you’re seeing. As reverse voltage approaches the breakdown voltage (Vbr), the current begins to increase until it is essentially an open circuit.


Thanks! Yeah, I understand what the reverse current of a diode means— just couldn’t confirm that that’s what Ir was. What I’m unsure of though is what applications the reverse current is relevant information for. I’m guessing it’s not too significant in any audio applications, but out of sheer curiosity I’m wondering where, even outside of audio applications, a higher or lower Ir is preferable.


----------



## benny_profane (May 20, 2022)

Bricksnbeatles said:


> Thanks! Yeah, I understand what the reverse current of a diode means— just couldn’t confirm that that’s what Ir was. What I’m unsure of though is what applications the reverse current is relevant information for. I’m guessing it’s not too significant in any audio applications, but out of sheer curiosity I’m wondering where, even outside of audio applications, a higher or lower Ir is preferable.


One practical reason in re pedal building is if a diode is used in a feedback loop for clipping. If the Ir is too large, that can affect the design of the gain stage. This spec is the main issue folks have with the G2 and low output.

Edit: An ideal diode has no Ir. I don't know of a situation where you'd want a specific Ir since the closer to zero, the better. There are special cases where that reverse behavior is an asset, though. Zener diodes are designed to have specific breakdown voltages when reverse-biased. The voltage assigned to a Zener is its breakdown voltage and they can operate in that region. They are typically used to prevent over-voltage conditions in a circuit.


----------

