# Oscilloscopes:2 Channel, 4 Channel, 100Mhz, 500Mhz etc.

Mar 13, 2022
43

#### kellys_eye

Jun 25, 2010
5,111

for the most part you might find yourself fixing SMPS devices, audio amplifiers, basic receivers and some digital stuff ALL of which can be done under 20MHz bandwidth. If you think you're going to fix microwave stuff or even VHF/UHF etc stuff with one then think again - that kind of equipment needs more than just an oscilloscope to attend to i.e. frequency counters, spectrum analysers, RF oscillators and sweep generators etc.

#### John R Retired

Mar 13, 2022
43
For a 'beginner' I'd suggest an analogue 'scope, dual channel, 20MHz.

Sounds 'weak' but there is no 'beginner' who's going to fix RF Microwave stuff! That's something best left to (lots of) experience, by which time you may have learned how to use a basic 'scope properly and utilised it to its full advantage.

One thing about second hand 'scopes is that they retain their value so there's nothing lost by getting a low-end 'scope and learning the ropes then selling it on afterwards as your skill levels increase.

The thing about 'new' 'scopes is the exact opposite - they are getting cheaper and have more functionality as time goes by so something you buy (expensive) today will be 'old hat' next year (well, not exactly but that's the basic principle).

As for an eBay purchase, you will have to rely on the sellers good feedback and/or the use of eBay's buyer protection scheme. Of course, when you buy a 'scope from eBay you have to test it but that only takes a few minutes however most 'scopes are a go/no-go purchase and problematic ones are easy to spot.

You can get a cheap analogue 'scope for $20-$100 - don't go mad or expect miracles. It takes time to learn how to use one and paying a fortune for an all-singing, all-dancing 'scope you have no idea how to use to it's full extent is a total waste of time and resources. A 20MHz analogue 'scope served me well for 30+ years - it's only recently that I've moved to a 150MHz version (digital) and I still regret selling the old analogue one I had (Hitachi - very reliable, did everything I needed up until recently).

Don't forget 'scope probes too - these make a huge difference to the operation of the 'scope and can be as expensive as a cheap 'scope on their own. I paid \$60 for a decent set of leads second hand.....

I used a Tektronix like this one in college. Tektronix 475 Dual Channel Oscilloscope with Service Manual | eBay

What if I come across for example, a 100 MHz close to the price of a 20 MHz as you recommend? should I pass it up and go for the 20? Are are you saying that there is a "practical" reason for sticking to a 20 MHz exclusively and ignoring a higher bandwidth for similar price range?

Regarding the condition and accuracy of a used scope, I would not want to get stuck with someone else's problem in that case.
I would not want to buy a used scope with some hidden defect I would not be aware of which would affect
mathematical accuracy. It would probably cost more to have an expert scope technician check it out than the cost of the scope itself.
I noticed you said that ebay scopes are a "go/nogo" purchase which I gather means they either work or don't work and that
in itself is all a buyer needs to know?

Last edited:

#### Kiwi

Jan 28, 2013
424
Would you recommend the digital types that connect to a USB port on a laptop, eg PICO, Hantek, etc

I have a TRIO CS-1022 at home, and use a Fluke 123 at work, but would like a bigger screen.

#### kellys_eye

Jun 25, 2010
5,111
Getting a 'scope of higher spec for the same price is a 'bargain' and not to be overlooked - to an extent - but quite often the higher spec 'scopes come with functionality you will probably never use and/or complications that confuse and make learning how to use one that little more difficult. 'Simple' 'scopes do what they do well, are much easier to both use and/or service (if the need arises) and spares are readily available - many big name 'scopes rely on proprietary parts made from unobtainable and can be expensive, let alone a right PITA, to keep in service.

Testing the calibration of a 'scope is quite simple - comparison to an accurate DC source for the Y-channel and the same against a stable frequency reference (xtal) for the X-channel. And if it 'locks' (synch's) with the measured signal that's pretty much all you need.

Where some 'scopes 'fail' (rather they 'lack') is a reliable synchronisation channel - the ability to 'lock' to a measured signal. This can happen (and does) far too often with digital 'scopes, less so with older analogue types and staying within the 'named' market gives you some safety in that respect.

Older 'scopes also have readily available documentation, operators manuals, service manuals etc that can save you a lot of time and trouble - if the seller has them that's a bonus but downloads are aplenty.

Don't buy a 'scope that the seller doesn't specifically states is 'fully working' - it's as simple as that. If they are lying you have buyer protection and can return it for a full refund. If you can, buy one locally and see it working before you buy - they are probably a lot more around you than you think!

As for plug-in (to laptop) 'scopes...... bleurgh..... (that's personal opinion though, some swear by them). They are generally overpriced for what they are and have the disadvantage that you need a laptop (or PC) to use them! Far simpler to have a dedicated tool for the job.

Since you have a TRIO 'scope already (a decent piece of kit in its day and still relevant) the whole discussion can stop. If it works and you learn how to use it to its full extent you will be 'geared up' for any kind of repair work that you will come across that fits in to your skill set.

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