Transistor Curve Tracer kit on ebay

[GreyWoolfe]

I am going to ask a stupid question here.  I just got one of the curve tracer kits that Fraser and wirehead got.  My kit didn't include the PCB mounted RCA jacks and the RCA to BNC adapters.  I just got a couple of bulkhead mount BNC jacks.  My plan is to put this in an enclosure with my octopus circuit tester. 

Here is the stupid question.  What is the best thing to use to connect the BNC connectors to the board?  Would plain wire work or is there something better? I even have a broken Chinese scope probe that I can salvage the wire from.  I just used short pieces of wire with the octopus and that works fine.

If the RCA jack is the best way to go, does this look correct?  http://www.ebay.com/itm/1Pcs-PCB-Mount-2-RCA-Female-Stereo-Aux-Audio-Video-Jack-AV-Socket-Connector-/400979088030?hash=item5d5c37529e:g:ViMAAOSwd0BV0OpG

Use the BNC connectors. Much better than RCA. Use twisted wires and keep these as short as possible. Connect to the scope via short Coaxial BNC <> BNC cable.

I've got mine in a repurposed enclosure as seen above. Due to the added wire length to the device-under-test (because of the switch), I've added a 1nF capacitor between the emitter and the collector. It gives sharper traces with less noise, whilst not interfering with the measurement. 

I will make a short pair of BNC cables like I did for the octopus.  The box will sit right on top of the Tek 2235 that I am using for the octopus.  I am sure that I have a 1 nF cap to add.  Thanks for the tip on using twisted wires and I will keep them as short as possible.

[McBryce]

I have one of these PCBs (assembled) that was part of a box of random PCBs I picked up at an auction. I don't need it, so if anyone (especially in Germany due to postal costs) is interested in having it let me know (send PM).

McBryce.

[DBoulanger]

Hi,

Although there is no post in that topic since a little while, I figured that it wouldn't any harm to add one.

I recently acquired this kit in a flea market where the person was selling electronic parts and boards, mainly for parts.  Some of the boards were intact, some of them had a rough journey !  For a box of may 30 boards or so, I ended up paying $20, which wasn't bad a all.

Anyhow, despite my efforts to understand what may be wrong, the calculated gain with the scope trace is always higher than the ones I obtain with my DCA55 for instance.  I have a transistor tester, a DMM and the DCA55 that give me similar values, within a margin of 20 or so, but the curve tracer is close to 100 more,

For instance, I tried with 3 2N2222 and the figures were roughly the same, in the 230-250 range using my "regular" testers.  The curve tracer gave me values in the 350 range.  I can understand that the current used to evaluate the gain isn't the same, but having values so different from each other, make me wonder if I missed something.

By the way, I found some RCA jacks that fits perfectly on the board, footprint wise.  I bought them on eBay, "Audio Video AV 2 RCA Female Jack Socket Chassis PCB Mount Connectors 5 Pcs", item #321695325968.  The ones that were suggested earlier in this thread, didn't have the same footprint.

Bye for now.

[suenrod]

I am considering the same. The price sure is right if it can be used for transistor matching.

[suenrod]

Any performance issues to report? Has Dave and crew ever done a comparison on these VS a real curve tracer?

Would this be a suitable curve tracer for matching RF power transistors? I'm not worried about measuring gain accurately. More of a subjective go/no-go comparison between transistors until I find a set that matches.
I would love to see how they fair up to a REAL curve tracer.

hint hint Dave

[steverino]

If you're a follower of Paul Carlson's youtube channel, Mr. Carlson's Lab, he mentioned he's going to be sharing a curve tracer device he designed and built.  I think he's going to initially release it to Patreon subscribers.  Stay tuned...

[DBoulanger]

Indeed, this will be something interesting to follow.

As far as the gain precision is concerned, you're pretty much right, this might not be the most important thing.  Being able to measure it, within a reasonable error margin, is however interesting since it makes the learning process a bit easier as you can evaluate results with formulas and then apply the theory.

When the results are way off, determining what is right and what is wrong might not be too obvious for the beginners.

If only the overall aspect/look of a given traces set is what you're looking for, to compare transistors for instance, then this curve trace might do the job for you.

I don't have power transistors so I can't really tell you how well this trace would perform while testing these.

Nevertheless, even if this is an old subject, it's always interesting.

[rstofer]

So, I was wondering if the Digilent Analog Discovery could be coerced into doing curve tracing...

Yup!
https://ez.analog.com/community/university-program/blog/2013/12/07/analog-discovery-bjt-curve-tracer-program

I haven't tried it yet but the description and posted image make it pretty clear that it will work.

[Anks]

HI looking for a bit of help. I bought one of these kits a while ago and I've lost the schematic and build guide that was sent with it. If anyone could please send me a link to the correct schematic for the ebay kit that would be a great help.

Thanks Kris

[DBoulanger]

Hi Kris,

The documentation, along with the schematics, are available on the Thaikits.com website.

The link is http://www.thaikits.com/index.php/download.html?download=15:ch-012-user-paper-and-schematic

The password to extract the schematic from the zip file is "jojo2520", which is in fact the eBay's seller name.

Hope that helps.

[Lbud4]

I have one of locky z's curve tracers -- posted on the first page. I have had mine for several years and it works great. 

http://www.ebay.com/itm/locky-z-039-s-Intelligent-curve-tracer-PCB-New-/112168145773

His software is fairly comprehensive and is fairly bug free.

[Bryan]

I bought the built earlier version from Thailand as it was so cheap. Works fine and is an interpretation of an Elektor design. Cr*p it is not. I bought this newer ready built revision but have yet to play with it.

You do get what you pay for, but cheap does not always mean no good. The unit comes with a schematic so can be easily modified to meet individual needs. Its basic but it works.

The built version is here:

http://www.ebay.com/itm/Power-Transistor-Curve-Tracer-adapter-XY-Oscilloscopes-NPN-PNP-Vce-10V/140547987228?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D29384%26meid%3D8f4b0b82c46a48f98457355e541117ce%26pid%3D100005%26rk%3D2%26rkt%3D5%26mehot%3Dag%26sd%3D141138017533&rt=nc

There is a utube review on it. Also available in kit form. A few gotchas the reviewer found though.

https://youtu.be/7exRUNCQ-hI

[McBryce]

Wow, could he have made it any bigger or uglier?

McBryce.

[rodpp]

Wow, could he have made it any bigger or uglier?

McBryce.

kkk ugly, for sure. But not  that  big:

[McBryce]

That Sony has to be that big. It's full of CRT and electronics and I'm pretty sure there's not much spare space inside. The other above could fit in a box 1/4 the size.

Btw: I have one of those Thai Curve Tracer PCBs (80% built) knocking about that I never intend using. If anyone is interested in buying it for their own experiments send me a PM.

McBryce.

[Anks]

Hi Kris,

The documentation, along with the schematics, are available on the Thaikits.com website.

The link is http://www.thaikits.com/index.php/download.html?download=15:ch-012-user-paper-and-schematic

The password to extract the schematic from the zip file is "jojo2520", which is in fact the eBay's seller name.

Hope that helps.

Thanks DBoulanger

[torch]

I bought one of these last year. Just got around to putting the main circuit board together last night. It works exactly as advertised. It gives a very nice, crisp, clear trace when used with my analog Tek 475. Not so much with my Rigo DS1052E, but that's the fault of the Rigol -- it has a terrible display in XY mode. Also, the scope needs to be bandwidth limited to 20MHz as the signal is kind of noisy.

The hfe calculation is 9% high when comparing measurements of a 2N2222 with the results provided by my Karl-Heinz type transistor checker when taken at the extreme end of the ramp. I found similar results with a small PNP transistor, making a total sample count of 2. 

I left the 2N2222 in there for a couple of hours with no heating. It was drawing 39mA from the +leg of the power supply and 17mA from the -leg.

I also tried it with one CXL154 (an NPN power transistor) in the high power mode. It worked fine with that too, with the +leg drawing 59mA and the -leg remaining at 17mA.  Slightly warm after 1 hour. That one measured 33 on the Karl-Heinz, 35 on the curve tracer, but the package claims an HFE of 100 (AC vs DC?).

I tried a big ol' IGBT and got a capacitor-like lissajous pattern that slowly rolled from left to right.

I have yet to assemble the power supply board and put it all in a nice case with switches and BNC connectors, but I think it will be a nice piece of kit when it's all done, when used within it's limitations.

[Calambres]

Sorry to restart an old topic but I'm getting this kit and I'd like to know if it can be used with FETs too.

[IulianP]

I was wondering... on the ch-012 from Thailand, what are those two big yellow things on top of the board?

[McBryce]

Relays.

McBryce.

[Calambres]

I have built one of these kits and it works fairly well but I'm having a problem I cannot address.
I can get quite clean curves out of this but only if I plug the transistor in its own board socket:






So far, so good, but I have added an outboard 3P4T switch and a ZIF (Zero Insertion Force) socket in the project box to allow four transistor matching easily, very much like Wirehead's project in this same thread, plus a couple of banana socket trios to test external power transistors:



The problem I'm facing is that this setup requires some cabling:



and once I take some wires out of the supplied testing socket, the curves in the scope distort big time:



I have tried using coaxial cables from the 4-pin socket to another 4-pin socket just to see if this could improve things but the distorsion is even worse:




It is courious that if I firmly grab the coaxial loom with my hand, the distorsion disappears completely:




I assume there are some stray capacitances in the external wiring but I have no idea what to do to solve this problem.

Any ideas?

[Calambres]

C'mon... anyone?

I'm stuck! 

[Bud]

The thing is oscillating. Try putting a few EMI supression ferrites over the cable bunch. A few of them.

Try to use twisted wire pairs for each of the lines. Connect one wire from each pair to ground on the board side. Leave these ground wires unconnected on the remote socket side or connect them together, see if one or the other way works better.

Edit: BTW the original article posted at the beginning of this topic says connection length should not exceed 10cm, they knew long wires will create problems.

Edit: the twisted wire should have a few twists per inch, not just loose twist like in network cables. You can use a drill to make a length of twisted wire.

Also what else you can try is putting small EMI chokes right on the legs of the transistor being tested.

[Calambres]

Thanks for your answer.

With EMI suppression ferrites you mean ferrite beads, right?

I know the 10cm warning in the original ELEKTOR article but this is not compatible with what I'm trying to do. I'll follow your suggestions and report them back here once done.

Thanks again.

[Bud]

Yes ferrite chokes, ou can use snap-on split chokes or regular ones since you can run your wires through the core.