#49: Simple Component Tester using Oscilloscope - Octopus Curve Tracer

This video shows an example of performing a simple component test (curve tracer) on an oscilloscope. The simple circuit shown is often called an Octopus (I don't know why), and it's been around for decades, in many variants. You can Google search on Octopus component tester, oscilloscope curve tracer, etc. and find dozens and dozens of variants. In the video, I boil the circuit down to its simplest implementation, describe how it works, and demonstrate how you use it.

[@rl2109]

I was introduced to trace analysis 25+ years ago when I worked at a component-level repair facility. I built my own octopus, bought an O'scope and got busy fixing my own things! The world is more interesting when you learn something every day!

[@iblesbosuok]

The world is more interesting when you learn something every day! (R L)

[@carlgradolph9676]

It may please you to know that, ten years on, you still have some interested viewers. Thanks for concisely demonstrating and explaining this piece of test equipment . Seeing it operate is both fun and illuminating!

[@captainjinx42]

I’m embarrassed to say as an engineer I never worked with the xy mode on my oscilloscope. You now have given me a whole new set of test tools with my 465 thank you so much!

[@andymouse]

Me too.

[@hasantamer9199]

merhaba hocam osiloskopa nasıl bağladı onu anlamadım siz anladıysanız banada söylermisiniz

[@sertacpamukcu]

@@hasantamer9199 Osiloskopun CH1 girişini X ve CH2 Girişine Y yi bağlıyorsunuz. Probların Groundları ortak bir tanesini groun olarak bağlamanız yeterli. Red ve Black Probes olarak gösterilen yerlere de bir çif kablo ya da Multimetre Probu / Krokodil uçlu kablo bağlayıp test edeceğiniz komponenti bu uçlara bağlayacaksınız. Osiloskop XY moduna alındığında X yönünde Voltajı, Y Yönünde akımı temsil eden bir grafik çizecek. Açık devre iken yatay çizgi (Direnç sonsuz, akım sıfır), Kısa devre iken Dikey Çizgi (Gerilim sıfır, Akım Sonsuz) vb çizgiler oluşacak.

[@hasantamer9199]

@@sertacpamukcu çok teşekkür ederim

[@Dexter-wf3yc]

There is a lot of complexity in the world of electronics even in the simplest circuits he he he

[@afterthought138]

The amount of practical and extensible knowledge provided in this video exceeds that of the first half of most introductory electronics textbooks. I'm consistently impressed with your videos and always look forward to the next.

[@radhikagupta7023]

I've been researching into electronics and found a fantastic resource at Gregs Electro Blog (check it out on google)

[@karkoon6364]

Spam links.

[@budapestprojectytc6002]

And he does so with only one hand.

[@rohitchaturvedi2271]

Radhika Gupta GTFO

[@AMS51000]

Back in the early 1970s, QST published a schematic for an octopus and I put one together, mainly because I had a cast-off all-tube, purple trace oscilloscope that must have weighed about 100# (my dad picked it up when his university chucked it). Anyway, I was about 14 years old, and I thought the octopus was particularly cool because you could test parts in-circuit. One day my ham transceiver (Henry Radio Tempo One) died. The power supply was blowing fuses immediately. So I decided to look around with the octopus, and rapidly found that one of the discrete silicon rectifiers in the full-wave bridge in the 500v (IIRC) supply was blown (I do not recall whether it had failed open or shorted). In any event, I was able to replace that rectifier and got many more years of fun out that transceiver. It's nice to see that these tools are still in use!

[@dmottern1952]

I first became with an octpus aboujt 35 years ago. It was in a U.S. Naval publication published for ET's. Very helpful little tester.Thanks for making the video.

[@andybrown3674]

Thank you. Used this type of device when learning basic electronics in the military in the 70s. Glad to find it again.

[@billygamer3941]

I always learn from your presentations. Either new information for me or a different view of something I already know (or think I know!). Thank you.

[@wrongmouse1658]

I was introduced to the component tester, while I was serving in the AF, in the early 70’s and this toy was old then. In the hands of an experienced technician, you could go through a bunch of transistor logic computer boards quick, this includes analog boards. It just takes about a few dozen boards to get the experience you will need for the transistor logic. The analog board where somewhat simpler, due to the fact the failures were sometimes more pronounced, but still had their quirks to work out. The short cut, for analog boards, was to compare a good working board with a bad one, when you had that luxury. Still have mine, that I used in my early days of board repairs. Update: Had to replace the BNC connectors as one was broken and had to get two to mach.

[@radiofun232]

Thanks a lot for this upload. Added to my favourites, very informative. Also your way to reduce the circuit to its bare essentials. Makes it simple to construct.

[@PatrickInCayman]

Excellent video, crystal clear explanation of how a curve tracer functions.

[@ericvandeweyer1766]

BTW, meant to add that your explanation is excellent.

[@mikem5043]

That is so cool. Now I want to rig up a tester circuit and check out a bunch of mystery components laying around. Love your videos!

[@MrMac5150]

This is the best, if I did not hear it from you, I would not have known about it, I think some of the old electronic teachers, have about 1 percent of your knowledge. Good Job.

[@1beejay1]

Thank for this video. Explains things in a clear and concise manner!

[@ThePopso]

Brilliant video. It explains the theory so clearly. Our component tester, the PinPoint II-R, uses this circuit to great effect, but I've never fully understood just 'HOW' it did it.

[@tanner1985]

Mindblowing. I didn't know of this, wonderful!

[@briand9513]

Been watching your tutorials, great info and thanks... Well done and very articulate.

[@samcast1005]

this is essentially a Huntron! Amazing video, thank you very much

[@ZilogBob]

Thanks for a very clear intelligently-presented video. :)

[@daverockwell5465]

Thanks alot!! When I saw this I remembered I had one in the garage that I made 35 years ago. Still viable today.

[@yz250ftony]

every bench at my place of work has this setup. mostly new equipment with these older scopes setup as tracers...very useful! tempted to build one myself for home.

[@cosmicfugue1226]

Yes my scope has a component tester and I used to use it as a double check that the component was faulty. It was very interesting back then. Thank you for the video and explanation.

[@ElPasoTubeAmps]

I built and used this test circuit for many years while working at WSMR when we still repaired equipment at the component level - as you mention above it is best used to make comparative measurements from known good to a circuit under test. I have fixed many problems using this circuit - thanks for posting it.

[@karlmartell9279]

Tank you, Mr. n'kay! This was very usefull and very good explained.

[@anonamos462]

Thank you for all these great videos.

[@qzorn4440]

Heath was a great self learning structure and I studied several electronic computer courses. thanks. 5 stars.

[@marpenman]

Very nice demonstration! I built one of these in a small box using a couple of BNC's and two pairs of binding posts, and I included a couple of switches to select a current sensing resistor (for 1.0 or 0.1 mA/V display), and an attenuation factor (x1 or x10) for the voltage output. Driving it with a function generator lets you see frequency effects, which is useful. On my 2246 I have to invert the Y channel to get positive current going "up".

[@brianhind6149]

Great descriptions as always Allan. I was admiring your 465B, in terms of its cosmetic appearance. I would hazard a guess that the 465 series of scopes must have outsold any other model. I have worked around the world, & any lab I had access to always had at least one, & often a number of 465's. Every commercial radio shop in North America had at least one. I also have a 475 that I purchased in a pawn shop, inoperative. The owner asked me for an offer, & I told him that I would have to take the scope apart & have a look before I would make an offer. He looked at me & said " Twenty-five dollars as is. !" I pretended to consider his price , & said " OK, I will take a chance & buy it " He handed me the scope & I handed him the cash, & he said " Hold on Q" He searched through a couple of drawers & came up with a box that had 5 Tek probes, that had never been out of their packaging. The cheapest one of them was over $200. He said " There are five of those like the ones plugged into the scope...give me $5 each for them as a package deal. The best deal I ever made Allan ! I traded three of the probes to an engineer friend & kept two, because I could use the. The 465B & the 475 & the probes are on my service bench to this day. I swear the militaries of the world all had those God awful looking military cased 465s.

[@silasfatchett5693]

Great tutorial, useful information excellently presented. Thanks.

[@1Rowdy1derful]

Back in my day this was a pretty high dollar piece of test gear called a huntron. I couldn't afford one so I designed and built my own much like you have represented here. Absolutely great video.

[@hasantamer9199]

merhaba hocam osiloskopa nasıl bağladı onu anlamadım siz anladıysanız banada söylermisiniz

[@sdscotto]

Another great video, Alan!

[@VE3MIJ]

I used to use a Huntron Tracker, which was commercially popular for trouble shooting in circuit. Worked great. Also built one in to my old B&K scope decades ago, that I grafted another CRT in to, after buying both for ten bucks each. Today, the only scope I know that has that function built right in, is the Hameg entry level HMO series, along with it's standard MSO capability. It's a great tool on any scope for component testing!

[@jez2391]

Absolutely love this video looks really useful, off down to the lab later to try it out. Thank You

[@techsinc]

Excellent video with very informative content.

[@karlomoharic3992]

You sir are amazing guy , so much information and at the same time so beautifuly explained

[@jbflores01]

excellent tutorial on how to use your oscilloscope to test components! now to make an octopus circuit!

[@burtlade1705]

Thanks for sharing your knowledge.

[@opera5714]

Back in the late 60'sI built about the same thing except with a transistor as a fixed current limiter and a voltage of about 300V. I did a lot of amplifier repair and bought the cheapest low voltage TO-220 transistors. The difference between transistors in a number series was that they were selected. You can't make transistors with particular voltage breakdown. Then I just selected out the higher voltage ones for amplifiers. Lower voltage ones were used in car radios. 95% of 30V rated transistors were well over 120V. On rare occasions I would get one with a squirrely point on the curve but still worked. That went to the dust bin.

[@johnohara54]

Great tutorial: I did BE+E school in the navy followed by radar”A” school but never did we get into the octopus circuit. I had a small stereo and CD player repair business to make a few dollars after getting out and ran into a former professor from Georgia Tech who briefly mentioned Octopus circuit. Interpreting the “L” from standpoint of voltage and current is straightforward. The oval for the capacitor is unique. I get a kick out of people with a batchelors degree making 50k to 60k while I made 120k at the phone company with an electronics education. LOL

[@EnricoCotulelli]

Thanks a lot, always learning something new

[@ericvandeweyer1766]

We used to use an Octopus many years ago when testing computer boards. We had a unit (later a Huntron) which had a ground and two probes and a circuit which switched between the two probes. Then the ground was connected to both a good board and a bad board at the same spot, usually the ground connection and then the two probes were put onto a test place on each bpoard and the patterns compared is the Octopus switched between the two. This was a very useful test tool.

[@leecampbell9498]

NOW I understand what it is that my bench tech here uses at the shop to check components out in cct Nice video awesome

[@JohnRaschedian]

Thank you! Invaluable video!

[@rbmwiv]

Great video. I have been using my octopus for a few years. I love it and use it a lot since most of the things I have to fix are broken due to a component failure. I work on cars and most of the time it’s a bad component or bad solder joint that has happened due to thousands of miles worth of vibration on it. I actually use the octopus more than use my scope in regular mode.

[@ReyciclismoMTB]

I love watching your Uber informative video. I know some are old but definitely useful. I love your super clean vintage tek scopes. I a couple of nice ones. But yours look new.

[@electron7373]

Excellent tutorial!

[@felixgasroorka1696]

Just great! It was very helpful. Thank you very much!

[@onlyeyeno]

@w2aew Still relevant, instructive and enjoyable ! Thanks for making and sharing :) Best regards

[@TheDrunkenMug]

Very usefull explanation, Thanks a 1000 times :)

[@spagamoto]

Well, I know what my weekend project's going to be. It will be a good use for my recently-acquired function gen :) Thanks!

[@clytle374]

I recently saw my first transistor used as a zener in the VFO of a Heathkit HW-101. Confused me for quite a while. Good circuit, good video

[@Bat8hitcrazy]

My experience with this tool was with Huntron ProTrack I. Loved it, I was a master at finding bad components. Now I'm using a usb o-scope and a scanner. Same thing but with far less capability. Still does the basics though, all you need on average is the low, med1 and med2. But changing the variables is pretty fun though!

[@rsattahip]

Thank you for an interesting video.

[@lochinvar00465]

This is a great tool to test homebrew crystal radio detectors. Trying now to build an old portable tv into a curve tracer using this type of circuit as the interface.

[@sudhirpatil3434]

Good - very much useful information!!!

[@kattasudhir]

great video and very useful

[@lochinvar00465]

I first came across this little jewel back in the Navy in the '70's. Was found in one of our technical issues. I built one and used it in the shop.

[@Uglydollsrises23132]

lochinvar00465 NEETS Module 19 has the schematic and goes into a lot of detail...funny though it never refers to process of "Easter-egging..."

[@Caseytheradioguy]

Love your Videos :)

[@TheCannaj]

Thankyou. very informative

[@coxsj]

Very helpful. thank you!

[@dd0356]

thanks for introducing octopuss

[@judd_s5643]

We dedicated a OS-8 oscilloscope as a dedicated Octopus. US Navy early 70’s

[@germisashvili]

Thank You so much for video!!!

[@bigdumbguy]

Thank you for explaining this to us. I wonder what limitations this technique has when testing components in circuit.

[@spectralcodec]

Another excellent video that makes me look at my scope in a new way! Thanks and keep up the good work!

[@garygrove1462]

Enjoyed the X-Y tutorial !! Gary Grove

[@Bianchi77]

Nice info, thanks :)

[@oapeland]

exelent as allways!

[@kirkpennock2997]

I've always wondered how they worked thanks.

[@radiodf]

I first encountered this circuit in Popular Electronics, 8/75. According to the article, this first appeared in a John Rider book in 1935. The name, Octopus, came from folks in the Navy. If you count the number of connections, including a grounded Line cord, you get 8 leads.

[@peterlamont647]

Neat! This makes me want to grab all the PE mags from the '70s - early '80s. Seems like all the coolest stuff you could build yourself came from/was popularized/widely published around that time period. It makes sense since it was the era of using solid state, but with the lingering memory of the tube era mentality of keeping the circuit dead simple, and very very sparse. If you can make a radio with 5 tubes, you can make a radio with around 10 diodes/transistors etc.

[@paulepruss]

Yup - I remember the Huntron and building an "Octopus Rig" in the Navy, '80-'85, AD15.

[@aronhighgrove4100]

The name octopus likely comes from the looks of common devices. A box (=head) with 5 leads coming all out from one sides (2 bnc cables to the scope, 2 test leads, 1 power cable, or when the power cable is at the back, a "nose" in the center, which is a trim pot/rotary switch to select the voltage).

[@wa4aos]

Hi Allan, Another Excellent video and TNX OM.. There was a commercial version of this device years ago called the Huntron. and it was a BIG dollar item. Seems like over $500 in the late 70's or early 80's. It may have had a few voltage sets but still a simple overpriced item but helpful. I have a Tek 576 curve tracer in my lab but use this simple tool for a quick check for leaky xsistors/diodes and use it often. It is handy to have a good example for go no go comparisons. 73, Glenn WA4AOS

[@kevinvanlandingham8938]

Are you plugged into the 120V outlet or function generator? Also, can this be done with a digital oscilloscope? Is the transformer necessary ? Thank you.

[@tamyboy1]

great video my friend

[@tjcool295]

very GOOD VIDEO!!!!

[@acoustic61]

Great video! I'm wondering if this tests components in circuit? I'd also like to know if it tests high power transistors and MOSFETS the way it's designed? Thanks

[@power-max]

Do most newer analog oscilloscopes (not the really old vintage scopes) have X-Y mode? I want get a scope for $50-$90 and would like to also have a curve tracer and spectrum analyzer.

[@ghadley1681]

Hi, Thank you so much for these wonderful videos, congratulations. I noticed that the flat trace corresponding to no current and also the sine wave itself is a bit wavey, is this due to the scope itself? And any suggestions as from where to buy such wonderful vintage scopes you are using, professionally refurbished and reliable? Just thrilling how the controls sound and the equipment looks and feels. Thanks so much.

[@aicisha]

Thanks! Very useful if you now have a digital scope and you miss the comp tester from the analog one..

[@jacka55penguin]

Loved the demonstration. Can't wait to try it out myself. I was looking for a curve tracer like I used to use at my old job. This seems much easier to deal with and not too difficult to build. Very cool.

[@rfrakes331k]

Thanks, Ron

[@Banzay20]

thanks for the video! so if you have a capacitor that starting to go bad, would you notice that with this tester or do you need an ESR tester?

[@electronicatutorial]

Hi, Alan what do you think of the top of your head what is a better tracer a Tek 577 (analog) or a Tek 571 (digital). I personally will go for the digital because of the screen readouts but I know the analog has a better control and response.What are their main differences? is price is about the same now.

[@FullElectronic]

Ok Thank you! This a great ideia. I mounted a version found in the internet,but dont works with small capacitors,it uses a transformer 60 HZ,using a function generator works great.How you did it,using a transformer or a function generator?

[@das250250]

Lovely to see this very good tutorial

[@SorinG2010]

Hi great video, I was wondering if you did take a look at your heath 4552 scope schematic in particular at the component testing section. I would love to see that. Could not find schematic online anywhere.

[@JohnRaschedian]

Thank you!

[@Pwaak]

Thank You!

[@bigslick]

QUESTION please Mr W2aew- I have same scope Heath 4552, but I read the manual and it mentions that this component test may damage some semiconductors. How big a risk is it with this Heath scope built-in octopus? The test uses 6vac and 11ma current. I mainly would be probing solid-state amps and preamps (such as Phase Linear gear) and similar. Just wondering whether I would be risking damaging the transistors and IC's? THANKS.

[@w2aew]

You'd really have to check the specifications of the devices that you're testing to see if the 6vac would pose a problem.

[@J4e8a16n]

Hi, Thank you so much for the answer. Which leads me to another simple question. Does the elecronic oscilloscope like the OWON SDS5032E-V, 2nd Generation of PDS5022, *New Upgrade* offer the same possibility?

[@xxxItchyxxx]

What a wealth of info for a beginner like me! That's really encouraging, thanks a lot!

[@bandulad82]

useful video ,good.

[@bloguetronica]

This is very useful! Thanks for sharing!

[@msk19991]

Thank you so much

[@robertruth3281]

QUESTIONS - What a wonderful video...and I just now FOUND it! Finally I understand how these work. If you see this... I have a couple of questions..... 1) will this test RF power transistors as well? Can you depend on this to evaluate a good vs bad part? 2) IN a discussion I just saw today (on the merits of doing COMPLETE Electrolytic cap swapouts in radios!)... ONE user said that they use an octopus tester on the electrolytic caps..... Circle? It is good..keep it. Flat line? bad! Replace it. That sounds simple....BUT ... is an octopus tester suitable for "in circuit" tests like that? AND....when using it "in circuit" will the display on the individual component be "reliable" OR can the surrounding components "throw off" the display form.... so that you could not detect a "failed part" or to me... more importantly.... a MARGINAL part? I would want to be sure that I can detect a "flaky part" that could go at any time (IF that is possible! But I would not want the "in circuit" use to affect my ability to test! I am just curious as to your opinions (and anyone else who may care to chime in!) on these questions. Thank you so much for this video!!!!!

[@w2aew]

This can only be used as a go/no-go tester when you have an example of what the "signature" of a GOOD one looks like.

[@tommywright6737]

Hello, I have an older tektronix oscilloscope which has xy mode, I made an octopus circuit I found online and followed the circuit diagram exact.The curve tracer is working but for some odd reason it seems that the patterns may be inverse as to what they should be. The examples from the link I posted shows the resistor signature as going up and to the right, when I test resisters I get the opposite, the angle goes up and to the left. Is it my scope or the circuit?

[@ciprianwinerElectronicManiac]

Thanks for sharing. Works very nice on every component except coils. Anyway, I just thought I gave it a try and it is a handy tool to have. I personally would not rely on such an instrument because it doesn't give number readings and such so it is a very limited tool from my point of view. Keep up the good work. :)

[@Stamatis_Misirlis]

Trust me for troubleshooting is way more effective than a number reading. Personally I use this neatmarine.blogspot.com/2018/11/mi.html The reasons component tester is better are: 1) Is instant, faster than your eyes! 2) No need to change probes polarity while check component 3) Check a component behavior in all intermidiate voltages and phase between voltage and current. If you go to component tester, you can't go back.

[@simontay4851]

Wow, that device is amazing! I never even knew it existed. it can do everything. How do i buy one?

[@andymouse]

@@Stamatis_Misirlis Your completely missing the point.

[@andymouse]

Your completely missing the point.

[@J4e8a16n]

I love this. If I undestood a bit. The shema you give is a replacement circuit for the in build component tester on your oscilloscope? Unfortunately I dont (see) understand your wiring. Would you show a shema? I have build your octopus but I cant figure how your red probe gives the volatage on every component you touch. JP

[@The1jonnyz]

Thanks so much for the quick reply, and thanks for the awesome videos... much appreciated!!!