Your probe looks nice and small... mine is large and bulky because the only parts I have laying around are almost all trough the hole types. 25:15 into the video you test the end result and turn up the sensitivity. Suddenly the set starts to 'scream' over the edge. My guess is that your simplification of Paul's original design has caused some oscillation; I think the 1K resistors with the 22µF capacitors that you omitted were there to guarantee a stable supply of almost 5V for every stage apart, without them influencing each other to much. When your power supply runs trough a potentiometer, a slight current drawn will drop the Voltage, and that starts cascading into oscillation. So giving each transistor something to chew on (a loaded 22µF) will be beneficial. Without seeing your video before, I also build the probe with the BC547C transistor. Because these are high gain types (hFE of 500-600) I raised all of 5 base resistors from 3.3M to 10M, because there is no resistor divider there, but only the 3.3 M for current limit, and in a breadboard setting I saw that these transistors were fully saturated, full open with only a few tenth of a Volt at collector - emitter. The original used transistor (2N3904) have a much lower gain. I will try to omit the first capacitor at the probes input as you suggested, why not.
Thank you for your comment, I may experiment with some more de coupling on the transistor supply but am limited for space! Anyway it works, had a faulty audio cable the other day, located a break on the screen within a few mm impressive!
I was thinking of putting the probe board and amplifier board inside a project box and use coax to go to a probe handle with nothing but wire in it. I don't like surface mount components. Do you think that would work?
Hi, no that is not the best way. There's a reason why the input amplifier is in the probe. You really need the 1st amplifier stage near the thing your probing. Its got a very high input impedance so connecting a length of screened cable to it will capacitivly load it & reduce its performance. But try it and see. You don't have to use smd devices like I did. Use normal sized components and use a bigger probe body. I just like smd and it made the probe small. Hope that helps, thanks for watching
Thanks, it was a challenge getting it in the probe body, not sure how much I'll use it as used to using a scope. I love smd more components in a small space and no holes to drill!
4 года назад
Can't find a parts list for it,, can't find a gerber file to send to a board maker,, don't want to make the board due to the chemicals, Could someone supply a parts list and a gerber file? It's really worth the build, but can't find the parts list etc even on Patreon. Ideally a parts list we can upload to a parts supplier?
@@acoustic61 if I remember rightly there's a part of the circuit that I didn't bother with for rf detection, I remember there being a switch for different modes
Thanks. I want to build one probe or another. Mainly for audio troubleshooting but also for occasional RF use. This one looks good too. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-OGrkIC-Mov0.html
Lovely Video Nick Wish I Could Work With SMD Stuff But I Like My Components Like My Women BIG Well Medium Maybe he he Havent Built Any Thing For Years Let Alone Used Some Ferric Chloride Brings Back Some Nice Memories Stay Safe Regards mike
Hey ptronix, nice job! Clever using a probe "tube" for the probe housing. Re: amplifier/speaker...could you use a computer speaker.. it already has a volume pot? Thanks for the video.
Thanks for the comment, yes you certainly could use a computer speaker but I wanted something fairly small that would run on a battery to make it portable & not mains powered. It was a struggle to get the components in the probe body but I think a good overall result although I must admit I rarely use it, an oscilloscope is more useful to me
Nice work. Too bad this guy decided to start gatekeeping pretty much everything else he's designed after this on patreon...oh well. Thanks for posting your results!
