What probe and other questions? - Page 1
Forum section: electronics / beginners

author: Juup
author_rank: Contributor
timestamp: July 21, 2023, 05:41:44 pm
content: Hi all. I bought an oscilloscope without anything but a big bookwork with it. My goal is to learn things to be able to repair vintage audio. I ordered a set of probes on Ali. But then i saw it was specific for 100Mhz. My scope is 200Mhz. So i bought another probe rated at 200 Mhz. Can i use the 100 Mhz probe or did i wrong to buy it? And if i want to change old parts in a tube radio, can i thrust an ESR meter ( Peak ) i bought to find the right condensators? I,m not that experienced. I just want to start somewhere.Thanks

author: David Hess
author_rank: Super Contributor
timestamp: July 21, 2023, 06:39:20 pm
content: As long as the input capacitance of the oscilloscope is within the compensation range of the 100 MHz probe, the probe will work fine.

author: Juup
author_rank: Contributor
timestamp: July 21, 2023, 07:00:40 pm
content: Hi David,Thanks for the reply. Here is my problem... I want to use this new ( old ) scope to learn. But if i fail at the start i never will be able to use it again. What can i do next after buying a scope with 0 experience? Are there some simple tests i can do? Is my probe the right one? Because i am collecting for some time now, i have also a tone generator, a lab transformer, soldering and de-soldering stations, loop-lamp/ cheap microscope, a big eighties east german variac/cleantransformer, 1943 tube tester and lots of parts old and new.

author: Juup
author_rank: Contributor
timestamp: July 21, 2023, 07:13:00 pm
content: This year i thought i go out and buy some nice tube amp with my holiday money. I did not and bought the missing parts of my dream. Don't care the best. If i am able to repair or even play with designing my own audio, i will smile. If i buy this, some other was smiling with his set-up. To dive deep you have to learn.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: July 21, 2023, 07:46:57 pm
content: Good Morning Juup, welcome to the Forum. Way up at the top of the first page of this thread is an oscilloscope teaching thread, (in the pink area), and there is a TON of good info for learning how to use your scope.Best of luck in your quest for knowledge.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 21, 2023, 11:00:28 pm
content: First of all, you are off to a hopefully good start.Your probes will not hurt the scope.The probes; capacitance as stated already should match pretty close to the capacitance printed on the front of the scope near the inputs.Try to align them with the adjustment using the test signal on the front of the scope.If they do not match or adjust the square calibration wave, they will still "work" but the amplitude and possibly the shape of the wave your are examining will be "off"Higher freq probes and scopes are usually lower capacitance.If you are starting with audio frequencies, the 100 MHz probes might just work fine.Spend some time watching the videos in the oscilloscope thread as already suggested.Look around in this thread.There are some recent threads about capacitors and ESR.Old tube radios have some high voltages please be careful. Always use a 10X probe not a 1X.1X probes are a unfortunate way to blow the input of your new scope.

author: tggzzz
author_rank: Super Contributor
timestamp: July 21, 2023, 11:20:37 pm
content: There are a few things you could to to damage your scope or yourself. It is worth understanding what they are in order to avoid doing them. One starting point are the safety and praxis references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/Have fun, safely

author: Juup
author_rank: Contributor
timestamp: July 22, 2023, 09:20:53 am
content: Thanks for the adviceThis must be enough to get a good start.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: July 22, 2023, 11:59:24 am
content: Look up W2AEW on YouTube. Alan is a customer support engineer with Tektronix and is an excellent presenter. He has a lot of videos covering the use of oscilloscopes and one specifically on probes:https://youtu.be/SX4HGNWBe5MSJ

author: Juup
author_rank: Contributor
timestamp: July 23, 2023, 03:18:52 pm
content: I will take a look at this. Thanks. I am already subscribed to this channel.

author: Juup
author_rank: Contributor
timestamp: July 23, 2023, 04:03:37 pm
content: I have a few more questions. My wall sockets have no ground connection. Only 2 pin connection instead od 3 pin. ( sorry for my poor English ). Is it safe to operate a oscilloscope if i plug it in to the variac/safety transformer? Are there better ways to solve this problem? In my kichen i have those grounded wall sockets. Is it an idea to use an extension cable from the kichen? Are there any thoughts on the oscilloscope, the Philips PM3220? Is this a good one for beginners? I have also a 10MHz oscilloscope but i'm not sure if it works well. This one does. Should i sell this and invest in a new digital oscilloscope? I like the old stuff much more.This is what i collected so far in my goal to set something up to repair old gear. Is there something important missing? I feel it is complete enough now to start learning all the things now. I waited because i am not in a hurry. I love old tube gear and i am very aware of the danger it brings. Some years ago when i was poking with a screwdriver in an amplifier i saw a huge spark flying in the chassis. That was very impressive so i want to be on the save side nowThanks!

author: tooki
author_rank: Super Contributor
timestamp: July 24, 2023, 12:42:41 pm
content: Use an extension from the kitchen for now, but ultimately, have an electrician install properly grounded outlets in your workspace.I highly suggest you get an RCD for your protection, but above all, read up on grounding and safety with regards to vintage radios, because many of them have hazardous voltages, including many with a “hot chassis” where the chassis itself is at mains voltage. You need to be aware of that possibility for your own safety. You may need an isolation transformer, and then need to understand how to use it safely. (Because isolation transformers eliminate some risks but also introduce some new ones!)

author: artag
author_rank: Super Contributor
timestamp: July 24, 2023, 06:55:13 pm
content: > Should i sell this and invest in a new digital oscilloscope? I like the old stuff much more.No. Sometime you might want some of the features of a digital oscilloscope but the analogue one is much better to start with if you really want to understand what you're doing. And I can think of nothing that a digital does which is especially useful for audio. Cheap ones are particularly bad as they have a greater chance of misleading you than an expensive one.Continue with what you have. Use both of them and understand the advantages of the better one (and the limitations of the poorer one).Don't worry about your probes. They won't affect anything unless you're working above 100MHz and maybe even not then. But do adjust them properly, with a square wave source such as the CAL pin. If you can't do that correctly they aren't suitable for your scope, though they will do no harm - they'll just mislead you with inaccurate measurements.I would want to have the scope earthed as I would any device that I handle that has a metal chassis. But if the practice in your country is to not earth a device such as an electric iron (or indeed a soldering iron), the scope is no more dangerous than those. At least not to you. It might hurt a more sensitive electronic circuit .. though that also might not be earthed.I'm sure some philips scopes of that era I've used in the past had a 2-core power cable and no expectation of being earthed. I wouldn't expect to add an earth cable to such a device. But if it is fitted with a 3-core cable, the best practice is to connect them all according to your local regulations. An isolation transformer will slightly improve things if that's the local safe practice. A variac is not desirable but I don't know your local conditions. Maybe it's essential to get the mains into the right range, but would worry about the possibility of it giving you too much voltage (eg if you set it high because local mains is low, but then conditions change and it is found to be too high). If that's the case a constant-voltage transformer or some sort of electronic line conditioner might be a good idea. Electronic equipment is not as tolerant as electric lights, heaters etc.Since you already have a digital scope (or, possibly, one that can be used either way) take some time to understand how they distort the measuremets. 250MSa/s means that it will display very surprising result above 125MHz and will show some oddities above about 25MHz. In fact, a brand new one suffers just the same problem but it's harder to see. Therefore, yours will instruct you better than a new one ! Read about 'aliasing' and 'undersampling' and try to not just understand it but see it in your own experience.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 24, 2023, 08:50:33 pm
content: Quote from: artag onTodayat 06:55:13 pmIagree with artag entirely

author: tggzzz
author_rank: Super Contributor
timestamp: July 24, 2023, 11:55:00 pm
content: Quote from: Wallace Gasiewicz on July 24, 2023, 08:50:33 pmThe USP of a digitising scope is to capture one-off events. That's unlikely to be the case with audio.Digitising scopes can also post-process captured signals to, for example, show frequency domain behaviour. I'm told some low-end scopes only post process what is on the screen, not the entire captured waveform, which is definitely "sub-optimum".Low-end digitising scopes are mostly 8-bit. That's a limiting factor for audio work, especially FFTs.If you are happy with an analogue scope, continue to use it. If you find something it won't do, then is the time to determine what would be useful - which might or might not be a scope.But do use every tool safely