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

Enjoyed the X-Y tutorial !! Gary Grove

Excellent tutorial!

Hey, great video! I have been banging my head against the desk trying to get this to work, but no matter what I do I always have the trace flipped in the y-direction. My scope moves the beam in the positive axis with a positive voltage, so everything seems fine. Any ideas on what could be going wrong? I have tried many designs out there and they all do the same thing.

want a copy of the orginal?
i have ;)

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

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.

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

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

Does not seem to work well with digital scopes, unfortunately.

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

Presumably the X input on the oscilloscope has to be inverted because the circuit shown has the earth (0v) in the centre, between the resistor used to measure the current and the voltage across the device under test. If the DUT is a simple resistor, the circuit will show a negative voltage for a positive current. Switching the X input to inverting fixes this.

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

How to identify base,emitter and collector in a transistor?

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!!!!!

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!

Excellent. Could you use a signal generator instead of an AC supply?

What a brilliant video. Is it possible to test capacitor and resistance for linearity using an oscilloscope in xy mode?😀

How do you measure the current transfer ratio in opto couplers? What does the current transfer ratio determine or influence in a circuit?

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.

I see the transformer output is 6.3VAC. If this voltage is applied to the resistors on board then it will damage the IC .

A capacitor will an oval. If it has ESR it will tilt the oval. Also you can spot noisy pots, as you move the control the trace will rotate vert horiz and back as you move the pot. If the pot is noisy the line will show noise spikes

Great video! I built an octopus such like this one and I was able to find a bad capacitor in a snubber circuit which prevented a switching power supply from starting.

I had another circuit's power supply which was overloaded and after almost pulling what is left of my hair off, the octopus helped me to find a short circuit between two pins which turned out to be electro chemical migration.

Thank you very much for your contribution. I wonder if this can also help in testing 3.3V modern TTL and microcontroller integrated circuits.

Greetings from Mexico!

Hi. Do you think this might be an option. Instead of buying. Huntron tracker. They’re very expensive. Thanks. Good video

I used a Huntron component tester at the company where I worked. It wasn’t cheap. It could do very high frequencies.

My professor at community college showed me how to make an octopus. It even had a current limiting potentiometer.

I built it and put it in an old project box from the C-band satellite positioner we got rid of decades ago.

This octopus is over 30 years old. I used it today to troubleshoot the rail switchers on an Arc 1000.1. It sniffed out bad A06 transistors immediately.

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.

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!

So interested intelligent good awesome
And fast and dont waste time

Thanks verry much

Where do you find a small 6.3VAC transformer? I want to make one but im mostly finding 6VDC, I dont know if DC would work.

I have never used an 'octopus' due to it being plugged into the wall.
But if it were hooked to a function generator, it would be able to check things at different frequencies!

I really like my old Hameg 404-2 it has a built in CT function

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!

Hii
This tester is very simple. You just need to make two-lead sine wave generators. x.y -0-180 degree phase angle inverse sine. Drive with popular ic8038 and even better ad9833 generator .or simple oscillator .transformer or transformerless .opamp. voltage is adjustable from 5v ac to 24v and frequency from 50hz to 1000hz. current should not exceed 1ma to 5mA. it is enough to know the logic of a resistor and a coil.

Does the line frequency matter? So far all schematics seem to assume a 60Hz line frequency, would 50Hz as in Europe, work as well?

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).

Question where did you find your Tektronix 465B Oscilloscope?

"I have a transformer from 220 to 12 volts. Is it possible to use it for this circuit? Very educational video!

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

I use them since education.....around 40 years.
a pretty good and fast method to work thru a unknown board.
With time you can tell it is a zener 12v or this caoacitor is leaking and so on.
I modified myo old hameg this way with swichable voltage and current (with limmitations ).
For fast repair it is best for me....
i have a modern component tester ....
but it is mostly not neccasary to desolder comonents with the oold method so i stick on that.
Sorry for grammatics and so on.....i am not a natural english speaker ;)
Best regards from Bavaria.

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

I was playing around and tested some zener diodes with Tek2245 and function generator. Everything looked fine, but then I realized that the trace was shifted some 1.5 divisions to the right. Then I just connected the function generator to the Ch1 in the XY-mode. I got a diagonal line, 1.5 divisions shifted to the right (cross point with the X-axis). When I turn off the funct.gen. I got a dot on the X-axis at that 1.5 divisions shift to the right. I tried 2 function generators, both 50 Ohm output. The amplitude of the func.gen. seems all right when I read the X-axis. If I change the Volt/DIV of the Ch1 the angle does not change but the amplitude of this diagonal line changes accordingly to the input voltage, so that seems to work right. Same with changing the offset voltage, it shifts this diagonal line (top-right to left-down) but along this same direction/angle. On my new Siglent I get the flat horizontal line as expected. Any idea where the shift and tilt comes from? TIA Maybe I need to look into the service manual 🙂 and turn some pots 🙂 ...

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

Nice info, thanks :)

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.

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.

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

47KOM слишком много, надо 4,7KOM. максимальный ток маленький.

For people new to these ccts, tell them Ch 2 Y axis has to be set to INVERT or they may get confused. Scopes are always grounded and the only way these testers match the text books is to invert the Y channel. Also let people know how to move the ground around and that's the real reason youuse a transformer is to float the ground. Using a function generator won't work.

Thank you. It is very good that someone explains so well the use of the oscilloscope to trace the curves that are so important in circuit analysis