first oscilloscope advice.

[peps1]

Hello, need to buy myself my first oscilloscope and was wondering if I could get some advice in what I should be looking for on a limited budget!

I managed to get by without one this long as I mainly deal with very simple analogue circuits where square wave diode clipping and 100,000 redesigned shunt-series-feedback amplifiers are the order of the day.

But as a move into more digital units with more complex ICs, PSU and charge pumps, having the extra tools like a oscilloscope are very appealing!

All I have my mind firmly set on is Cheap and 2 channel, so advice on makes, models, modes, and MHz are welcome! :D

[Mark R]

Depends on your budget really,
take a look here

http://www.stewart-of-reading.co.uk/Oscilloscopes.htm

[Yorkie]

Whatever you get on a limited budget will be quite old, and in my view, you're much better to get as simple a cope as will meet your needs as you'll stand a better chance of repairing it, plus less chance of it going wrong.

Whenever test gear is mentioned, there will be those who suggest 'buy the best' and brand names such Textronic, Fluke, and Avo trip off he tongue. But I think that all too often, where scopes are concerned, keen enthusiasts buy aging Textronic scopes with plug-ins, and storage scopes, that are so complex, that not only do they far exceed the needs of the individual, they never really know if the scope is working right or what settings they need to set it to to get a trace.

I'm not belittling anyone when I say that, but I think something like a 10Mhz Hameg or something similar - Trio or whatever, which can be had quite reasonably, will suit most people's needs admirably.

If you google secondhand oscilloscopes and check out e-bay to faimiliarise what you can get for your money, you'll get a better feel of things. A lot of scopes have been little used - others have been worked hard on a daily basis. The simpler the scope, then the more modern it will be for your money.

This will give you some idea of what's around:

http://shop.ebay.co.uk/i.html?_nkw=oscilloscope

If you can, from your own piece of mind and the vendor's, I think it's wise to try to buy one that you can inspect and collect personally. Scopes don't travel well, and there are scores of 'war stories' about them arriving with a smashed irreplaceable CRT, and all the hassle that follows such incidents. What you spend on petrol to collect it, you'll say to some extent on not paying P&P.

Of course, if you want one with a guarantee, that means paying the price from a reputable dealer, and in that regard, Stewarts of Reading tend to be the benchmark.

I use an aging Gould 300 10mHz dual trace scope, but rarely use both traces. If I'm checking say a decade divider, it's just as easy to put the probe on the input, then on the output of the IC to observe that it's doing what it should be - dividing the input by 10.

Though they tend to be seen as a 'must-have' item, scopes have little application in radio restoration, more so for TVs, and even more for digital applications which you seem to be involved in. I suspect that many, once bought, stay on the shelf.

Those are just my thoughts and observations - others may adivse you differently.

Hope that helps a bit.

Best of luck in your quest!

David

[peps1]

Thanks Dave and Mark, excellent advice.

Thank you!

[Mark R]

David
I tend to agree, I have a Telequipment D1011, a nice 10 meg scope, dual trace that is very rarely turned on. I also have a 10meg portable job from Maplin, really nice little thing, I think I have used it twice since I bought it.
For TV stuff though I think a higher bandwidth would be better suited than 10 meg.

For realignment a scope in radio repair is quite handy, but how many radios have needed realignment?
None of the ones I have done.

cheers Mark

[AlanBeckett]

Though they tend to be seen as a 'must-have' item, scopes have little application in radio restoration, more so for TVs, and even more for digital applications which you seem to be involved in. I suspect that many, once bought, stay on the shelf.

I'm sorry David, but I can't agree with that. It is true that a 'scope, and indeed a Signal Generator(s) are not necesary to repair a Vintage Radio. However, that's simply because once upon a time it worked, and put simply, all you have to do is get back to the state it was in when it came off the production line. Having a 'scope and a signal generator allows you to look at the actual signals and appreciate what's going on. It's all very well saying 'it's am', but do you really understand what it means? By the way I don't mean you, just a general you. A picture on the 'scope is worth a thousand words, and I would suggest that it's even more true with TV. I read lots of Posts saying things like 'The Field sync is dodgy, what do I do?' and I want to say 'Well what does the signal coming off the Integrator look like?'
I know, I've spent two thirds of my life looking at 'scope traces, on some of the best units on the planet. Having said that, just as in the Mechanical World where I wouldn't be without a Drill and a Lathe, in the Electronic World I wouldn't be without a Meter, a Sig. Gen. and a 'scope.
Alan

[Joe]

I suppose it's like so many things, Alan, that when you've got used to having it you'd miss it but if you've never had one it isn't so much of a problem. Also just buying one doesn't give you the skill to interpret what it's telling you.

As you know I too am on the look out so will be following this with interest. I have to confess though that it's a pretty low priority, in part because I'd have to find somewhere to put it. :D

- Joe

[AlanBeckett]

Joe,
I don't always get my 'scope out. Indeed, for that last Pye - I can't see the stats 'cause the Forum Software is antique - I didn't need it. However, let me ask a question; How do you think of the signals that exist in one of your radios? For a Superhet it starts off as an Amplitude Modulated rf signal at the aerial. It's then mixed - multiplied - with the local oscillator and the difference signal (usually) is filtered out by the IF transformers. That signal is amplified and then rectified (demodulated) to produce an Audio Signal, which is then amplified and used to drive the speaker. Wouldn't you like to see those signals? Not for diagnostic purposes, but to say 'Ah, so, that's what it looks like'.
Alan

[Skywave]

From my viewpoint, I basically agree with Alan (as above).

Test gear and the whole philosophy of T & M (Test & Measurment) is a topic that I have had a lot of experience in. It is a subject dear to my heart: I'd like to take this opportunity to express my thoughts . . . .

When, as a youngster, I first took an interest in wireless sets (as they were then called) and started experimenting (thank you, 'Practical Wireless' & 'Practical Electronics'), my knowledge was limited and basic: I trusted the designer of the item I was building / copying. Many was the time when the finished item didn't work correctly - or didn't work at all, despite carefully re-reading the build instructions, my assembly, etc. Of course, many years have passed since those early days, which have now included about 45 years employment in the electronics industry. I now appreciate what a difference my initial learning curve would have been if I had had (a) more understanding of what was actually happening in those projects and (b) some decent test gear - with the understanding of how to use it - to see what was going on - and what wasn't. In a phrase, a picture says a thousand words.
Look at it this way: suppose we could buy a second-hand 100 MHz dual-beam 'scope, working, for as little as £20. We'd all own one; they'd be as common as AVOmeters. And, by the same argument, a spectrum analyser is a very useful tool too. Again, I do believe that it is only the price that these are that renders them nearly always totally out of the reach of amateur enthusiasts. But like a good 'scope, once you've used one, after a while you wonder how on earth you got along without one.
The core of the real problem with electronics (and electricity) is that unlike most mechanical things, 'electronics' measurement is all down to trust, based on theory: you can't see just what those damn electrons are doing - or where they're going! Yes, trust: trust in your understanding of theory, trust in your kit, trust in your ability to use that bit of kit correctly and comprehend what you observe. And to complete the analogy with mechanical things, quality tools in the hands (and figuratively, the mind) of a skilled and knowledgable user makes the task so much easier - and yields a quality result.
Tools: always buy the best (yes, this indeed does usually mean expensive ) that you can afford. And then look after them. At first acquisition, you may think "I don't need anything this sophisticated!" However, as time passes, and your experience and comprehension grows, you will realise the wisdom of not buying a cheapo, limited budget item.

I hope that lot is of some value; merely my opinions & thoughts, based on my experience.

Al.

[Skywave]

How do you think of the signals that exist in one of your radios?
Wouldn't you like to see those signals? Not for diagnostic purposes, but to say 'Ah, so, that's what it looks like'.
Alan

'Diagnostics' begin with a complete understanding of what each component does, why it's there, why that value / item was chosen, the ability to estimate what the voltages and currents will be in various places (correctly working item) by a detailed study of the circuit diagram. Then if simple d.c. tests fail to reveal the fault - out comes the 'scope and related test gear: time for an in-depth analysis. Is what you now discover is happening different to what you predicted? :s If it is, why?

Al.