I watched the video, and since I have a lot of SMPS laying around, I was interested in finding out how you wired it up to oscope and what settings you use to display the noise, and how you wired that X-Y cap into the circuit – seems like a interesting experiment / test to run on various SMPS
I too looked if anyone was asking this question. Hard to say, but considering the sensitivity was rather low, a x10 or x100 probe ac coupled was used. However, filtering off the primary voltage and just getting the noise is the question. I saw another component tied in that reassembled a resistor but hard to say. I can try to replicate the setup but I’d have to find a noisy supply.
Radios + Tubes + Scopes + Cars= Nothing better!
@radtekman Wouldn’t any random recently made wall wart or AC to USB charger tend to be noisy? That is what I was planning to experiment with
@teufelwolf Probably, I have a Milwaukee charger that makes audible screeching, I can imagine what the spectrum analyzer would show. Although I would expect a better design from them over some random cheap wall adapter.
Radios + Tubes + Scopes + Cars= Nothing better!
@teufelwolf Well I played around with stuff tonight. After reviewing the video, it appears to be a 68 ohm resistor (hard to read the colors?) and a capacitor, of very light value I assume, in series. The probe is connected across the resistor. My experimenting with that part didn’t yield good results, however I found that laying the probe over the Milwaukee charger in question did the job just as the video. Replicated the scope setup with my 535A as I didn’t want to bother with the 556. Not to my surprise it behaved just like the example. On the HP 3585A it showed garbage from the bottom all the way up to around 20mhz. Only thing left is to open it up and see what they got going on inside. It was fun to play around with, like I said it had to be bad if I could hear it without equipment.
Radios + Tubes + Scopes + Cars= Nothing better!
@teufelwolf thinking back I should add, laying the probe over it won’t indicate if the noise is going back through the line, only what is near it. In reality the line voltage needs to be filtered out so you can display only the noise, however easier said than done. More info on this topic would be nice.
Radios + Tubes + Scopes + Cars= Nothing better!
Yeah I think my work lamp wall wart is insanely noisy – I was getting all sorts of weird measurements on my oscope when I was trying some simple Op-Amp experiment with a LM741 and a low voltage 0.3 Vpp input signal was degraded until I moved the desk lamp power supply to its own filtered power strip.