Thanks for the Video Heatkits are crazy expensive but i just order 7$ worth of parts that i didn't have already to make this, definitely the best Signal Probe design i have seen on youtube i have been looking for a while now Thanks again
Charles, I made 2 probes. One was made with name brand transistors (motorola) and worked great. The other probe had some generic transisters from epay, not a sound. I put in two of the name brand transisters in the non- working probe and it worked great. A very enjoyable project. A tool I wanted for a long time. Thanks for all your work researching it, and laying it out in a simple straightforward manner.
Nice job! I love the design of this - a no BS, straight forward, get the job done tool. I've got everything but the copper pipe in the shed! I needed to get some copper pipe for an earth ground anyway so I'll have that shortly and I'll get this built. Thanks for sharing!
My probe is working! I just couldn't get it to pick up audio coming from my phone. I finally got out the radio I"m wanting to fix and it picks up fine touching components even with my PC speaker almost all the way down. It picks up sometimes a little before I touch down. I really like the probe! 😃 A mildly shorted external speaker has killed the audio volume on talk back and receive in my Stryker 955. The longer the radio is on the quieter it gets.
I will leave the troubleshooting up to you. There are many excellent videos already out there showing troubleshooting methods and how to use a signal tracer. There are also videos showing how to make other types of probes and how to use them.
@charles Smith, thanks for the video. I will be building this somewhere the coming months, I hope. Need time.... ;-) However, what software did you use to make the schematic? Looks very clear, neatly organized. Especially the connections you've drawn on the breadboard layout, which are really useful to me. Thanks for a great project!
I use an obsolete program called QuickCad V8 which was produced by AutoDesk. It is a 2D software and produces perfect prints. This version works with Windows 10 but is no longer supported. Punch ViaCad 2D is inexpensive and will produce prints of comparable quality. There are quite a few drawing programs available for 2D drawings but a lot of them are here today and gone tomorrow.
I just bought a wireless electrical test light. It uses my body for a ground and is so sensitive that if I touch big pieces of metal, like my tool box or anvil, it lights up from what I assume is static electricity. I have to remember not to wear rubber gloves while using it. They insulate my hand from the ground contact on the handle.
I'm wondering if having the diode at the front like that and depending on just the strength of the test signal to forward bias it is best or if it would be better to have the diode in the output stage of the first FET for even higher sensitivity.
Does it matter how long the tubing is and the coax part for the input ??? I think I have some very stiff rg 240 or 400 double shielded 50 ohm coax I can use for the probe part of it ....
You can copy the simple drawing and layout from the video. It is only one page. It shouldn't be difficult. I have not posted the schematic anywhere else.
I have looked at a lot of signal tracers...and still dont know why someone(I have) has not used a oscilloscope probe.. It has a, what I would consider a pass thru setting(X1) and a 10 meg ohm setting...The probe wire is shielded which helps too...just my two cents wort.........
Charles, could you show us how to build this same probe but with a probe with just a wire coming out of a box? That way the circuit would be in the box and the probe would extend out of the box via a wire. Would that be possible or must it all be contained inside the tubing?
Not sure I understand your concept. The copper tube is easy to hold and completely shielded. Please build one using your idea and let me know how it works.
Try anything you like. These Jfets are extremely sensitive with good amplification but you can certainly experiment with other types. Just build a mock circuit layout on the bench and tack in whatever transistors you want to try. If you want to try op amps you will have to provide the necessary support circuitry. The video is mainly to show you how to construct the signal tracer probe along with readily available computer speakers. You don't have to buy an old signal tracer and then search for a worn out probe sold separately. That's the good part. There are many ways to configure electronic circuitry. Go for it if you want to experiment. That's the fun part.
Brilliant idea Charles, would this possibly work with one long aerial co-ax cable with just the stripped end poking out of some thin pva pipe as the probe, if you resite the FET signal amplifier circuit to a small project box beside your audio amplifier? In other words is it vital to have the little FET signal amplifier built inside the probe? Please excuse my lack of experience in audio/RF work. Thanks
You don't want a long probe and the transistor needs to be very close to the probe to prevent hum and noise. You are dealing with some very high impedance at the tip and you want to shorten it as much as possible. It's like an amplified microphone. You could possibly package it smaller but it would be your own design.
Great video, Charles. I'm trying to figure out your set up and i'm wondering what's up with the diagram that show's the short wire soldered to the copper pipe and the alligator clip? it look's like you used the short wire soldered to the copper pipe with the alligator clip on the piece of sheet metal to make the noise with the pocket screwdriver and also attach it to the small radio to show it working. I understand the positive power going into your end cap from the power supply, but where is the negative power from your power supply going to? The ground is going through the audio socket and the end cap retained by the nut on the audio socket as well. I got this part. I would think you would just solder the negative supply off the power supply directly to the copper pipe, But it's the short wire and alligator clip I'm confused on. Also i found out that the Stereo audio socket need's to have the correct polarity in the plug. The 1st time i hooked mine up to my computer speaker's i thought to use just the main speaker and found i had to use the Other speaker that was daisy chained off the main speaker to hear anything. I did try to tie the audio source into both input's to the stereo audio jack and that's when i fubar'd something and now the probe doesn't work. So i'll make plans to build another probe. Since there isn't a stereo circuit going into the audio stereo socket. I would figure that I'll just use one speaker and not clutter my bench with the two speaker's with the sound only coming out of one speaker. Thank's Scott from Colorado
The black wires are negative leads from the power supply. It is soldered to the copper pipe. The alligator clip is also connected to the negative of the power supply. It is used to connect to the chassis or battery ground of whatever you are probing. The shield of your audio cable is also connected to audio jack which is also part of the copper ground. All grounds and shields must connect together. Be careful not to connect the ground wire to any voltage source other than a chassis under test or you may get an unwelcome surprise.
@@charlessmith833 Ok Charles, I got ya now. Since i didn't attach my parts to the perf board like you did, I'll make up another that i can make any part's replaceable. I thought i'd run outta room on the board so i started from the coax probe end and worked my way to the other end. As far as the 2 computer speaker's since my 1st try played out of the daisy chained speaker and not the main speaker that the power supply connected to, I'll mess with that when the time comes to get the correct channel to come out the one speaker, Or i'll swap out the stereo plug on the computer speaker cable for a mono plug since i only want to use one speaker. Thank's for your swift return of my message. I also sent you a e-mail on this subject as well so you can disregard the e-mail. Thank's Scott from Colorado
I am also bit confused on the units of the capacitors. I heard the 22pF. I didn't catch the units for the other capacitors on the circuit. uM, pF, nF, I'm not sure. Please advise.
The .01 and .001 and .47 are uF (micro farad). The 22 is pF (pico farad). The 10/25 is electrolytic (10 microfarads at 25 volts). These are all standard values.
Hello Charles, I"m new to radio and was wanting to know if this would also work on FM radio ? Also, can you trace IF and audio frequencies ? Nice design and thanks for sharing it. That board that the circuit is built on - do you just solder the components to the back side? or do you have to connect all of them together? I'm have never assembled anything like this before. Clay
Will work on all RF and audio. FM requires a different type of demodulator but you should be able to hear something. The components leads are simply bent into place and soldered. No PC board, just a perf board. When you touch sensitive RF and OSC areas with the probe it will detune the circuit somewhat but should allow you to see if signal is present. An oscilloscope probe will do likewise. Using the probe along with an oscilloscope should give you a lot of troubleshooting ability.
I have mine built now but and a bit confused as to where the ground from the power supply goes. The schematic only shows a 2 ft lead to an alligator clip.
The power supply ground solders to the copper barrel. You can solder your alligator clip lead wire there also or run it separately from the power supply so it doesn't get in the way.
Don't know why you would ask. All the components are shown and named at 10:09 in the video. (I once knew a Jimmie Mack from Columbus Georgia while I lived in Opelika. Is that you?)
Hi Charlie, I just came across your video, just what I was looking for. Great project. Do you happen to have an DIY RF generator to inject into radios that can be followed by your probe and can also be used for tracing wires? Not sure whether you are still active. Please respond
Sorry, I don't have any plans for a signal generator. You should have no trouble purchasing a signal generator or injector online or finding plans to build your own.
I'm a complete novice. This probe is capable of picking up both AM and FM radio frequencies, correct? What about audio frequencies? Or are these all the same when it comes to tracing?
They are JFET. I have bought hundreds on eBay. They all come from China now. I haven't gotten a bad batch yet. You can use a 2N3819 but the pins are different from the MPF-102.
@@RC-Heli835 I don't understand your question? All you need is a power supply and an audio amp. You are on your own as to what audio amp you use. I like the computer type speakers myself. They already have the correct audio plug so you don't have to change anything.
I did the 12 to 18 v version with 4700 ohm resistors and it just will not work. I used RG8X stranded core coax and messed up and ordered gynormous 1/2 watt resistors. I managed to install it all but it simply will not work. I just changed the front mpf102 this evening and still no dice. Did you tie the stereo leads together?
Is the 1N4001 backwards? Are the MPF102's reversed? Check everything out again. Be sure. Yes, you only need one audio channel but you can tie them together if you like.
The perf board has a ground bus that attaches to the ground side of the RCA audio jack. It, in turn is grounded to the copper cap. That is your negative line. The power supply negative is soldered to the copper pipe on the side.
I was wrong. The ground bus comes out of the copper cap through a drilled hole and solders to the cap. Then the power supply ground solders to a different spot on the side of the pipe. Sorry about that. I reviewed the video which does show that.
@@charlessmith833 Ok thanks! I'll try that this evening when I get in! It's buzzing and I can here it pop if I touch the tip but it won't pick up audio or scratching on a thin metal plate.😃
Excellent probe, excellent video and remarkably good schematic/layout diagrams! Could you just confirm the capacitor values Charlie? Think you say one is just 22 Picofarad....are the other values in nanofarads? Thanks
Hi Mr.Charles,probe looks very nice, i have a question,is it possible to duplicate second transistor circut ,before conecting output jack to add 1 more transistor and duplicate circut for more amplitude???, i hope you understand me what i like to say
@@1ologarden Use can probably use N-FET that can take the 24V. I cannot verify the ones you mention. The biasing may be different for those transistors. Try making a test circuit on your work bench before building the probe.
Hi Mr.Charles, i build probe ,all parts on pcb board and shielded, i use as case old vacum pump for the probe, circut run on 22,7vdc, i use all original value parts from your discription,except- i use transistors BF245B - jfet , and i use diode OA79 - germanium,,all parts are propertly by your shematic inside probe and nothing touch ground.,now when i touch some audio signal with probe,the sound is not clear or bearly i hear them,probe working,i have clear start,its a very sensitive with touching fingers,or flying around devices, my computer, my laptop,my wifi antena, have a noise, i can got is why audio signal bearly hear them,sounds like a grgrgrgrrgr )))) not clear at all
I intentionally showed the whole schematic in the video. It is not a complicated drawing. Just copy it down. My drawings are on .CAD and will not convert to anything that I can post and taking a picture is no better than what you see in the video. I sell paper copies of more complicated items. Thanks for watching.
If you use a meter probe you will get overpowering hum being picked up along the entire length. You must use a shielded probe with very little exposed at the end. Stiff coax with a solid center is the best option. The shield is very important to controlling AC radiated in the air in all directions. If you lived on Mars and used battery power it probably wouldn't matter.
I was scared you would say that but was hoping. Great lay out you done on this. I built one like your first one but like yours it was way to low volume so this one should do the job. Thanks again for posting this very nice probe for us.
@@charlessmith833 I need one!😀 A slightly shorted to ground speaker has killed the audio level in my Stryker 955 export radio and I need to trace out the problem.
Charles, could you do me a huge favor and go to my channel and watch the short video on signal tracing questions ? I'm struggling to find the reason for this FM radio kit not playing. I'm basically wondering if the signal is supposed to pass through capacitors and resisters. Where am I supposed to hear tone and where will I not hear anything. Thank you
The MPF-102 JFETs I have bought are real. They are probably new, old stock. I buy them in quantities of 40 or 50 because I use a lot of them. They are extremely sensitive, with high gain and work well with a 24vdc supply. I have blown a few from carelessness but I have never found a bad one in my shipments. China is about the only source of small electronic parts anymore. I cannot find much in the US. You just have to be patient and wait two or three weeks for delivery. The only part you may have trouble getting is the 1N34A. They are widely advertised but when they arrive you find they are actually something else and will not substitute. I have gotten real ones on Amazon believe it or not. You will love your new probe when it is finished. Enjoy.
can I use a diode that is clear with a green or black band around it...I go some from some old stereos I take parts out of...the radio was probley made in the early 70's...It is a germanium diode for sure...
You can try using any germanium diode. Some of the old tracer probes used 1N48. If your diode is not as sensitive as what you see in the video then look for a true 1N34A. A silicon diode won't work at all.
