Looking for a transistor tester

bowanderror

Well-known member
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 :cry:
 
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Big Monk

Well-known member
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 :cry:

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

Well-known member
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:

JFET Matching Calculations.png
 

danfrank

Well-known member
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

Well-known member
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!
 
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fig

Village Idiot
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. :ROFLMAO:
 

fig

Village Idiot
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!

RkG3yng.jpg


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.

K0msRA3.jpg


fCgAYO2.jpg


BZmecu1.jpg




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

StompBoxParts

Authorized Vendor
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.
 

fig

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

Big Monk

Well-known member
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

Well-known member
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

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

Village Idiot
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:
BgBnSWr.jpg
 
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StompBoxParts

Authorized Vendor
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!!!!).
 
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Kroars

Well-known member
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.
 
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