Oscilloscope query.....

Kalimna

Greetings all,
I am slowly working my way towards making a start on the Modulus Amps kit I have currently sitting in our 'music' room.
I suspect that a 'scope might be a useful thing to have for troubleshooting both the amp kit and any pedals I throw together from tagboard schematics. I have no desire to buy new, so could anybody offer any advice on what to look for in used models please? Any makes to look for/avoid? How many channels am I likely to need? Do I need a signal generator to use an oscilloscope properly? I would be happy spending up to £200, but preferably not that much.... (and having looked on eBay, I realise that several thousand *can* be spent one)
As always, many thanks in advance.

Adam

m_c

I've got a PoScope Mega1 (https://www.poscope.com/product-category/measurement-instruments/) which does me for the odd occasion I need to use a scope. I've had it for years. It's pretty basic, but the software works well enough, and it doesn't take up much space when not being used.

However, the new cheaper standalone digital oscilloscopes are probably just as good in terms of oscilloscope use.

It's probably worth going and doing some searching/reading over on the EEVblog forum to see what the latest suggestions are - https://www.eevblog.com/forum/index.php

Emp_Fab

It's ten years old but the advice is still good...

https://www.youtube.com/watch?v=Xh9FNRpta9s

Emp_Fab

Also more recently - https://www.youtube.com/watch?v=Iq4QlfH-oqk

gringopig

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Kalimna

Hi folks,
Many thanks for the advice, particularly the eevblog forum rabbit hole!
I shall watch the videos, and see if I can find something appropriate. 
I suppose I should be asking - is an oscilloscope a near essential item for building valve amps? Or is it more of a luxury item that is handy to have?

Take care,
Adam

gringopig

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Kalimna

I have one of these dmm's. Not the cheapest, but far from the most expensive!
https://www.ebay.co.uk/itm/VICHY-VC97-3999-Autorange-multimeter-New/283687775020?hash=item420d1beb2c:g:7NkAAOSwHP1d26cp

gringopig

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Kalimna

Well, as far as I can tell, it works. Though was £4 cheaper when I bought mine.

m_c

One thing to consider, is for audio work, you don't really need anything that high spec. The audible spectrum is only 20-20'000Hz.

Combine that with what you're likely to be using it for, which is simply to see if you are getting an appropriate signal, spending lots on something that's accurate to nano volts and seconds isn't going to do anything other than help lighten your wallet.

ICBM

I would say an oscilloscope is very useful but not essential for simple building and maintenance. Most of the things you would need it for can be done by other work-arounds, although sometimes it’s extremely useful to see a picture, especially for finding more mysterious faults.

It’s also a great tool if you’re curious about how things work, though - by seeing where and how distortion occurs you can learn a lot about how amps and pedals work, and why they sound the way they do.

I have an old CRT Panasonic dual-trace 40MHz model which is easily good enough for audio work - you should be able to find something like this in perfect working order for under £100.

A signal generator is also useful but can be extremely simple - anything that produces a sine wave in the audio range will do, or even less than that. At the most basic, even a fixed 1KHz signal would work for most purposes. I do have a proper generator, but I also sometimes use a Fostex TT-15 test tone generator (intended for setting up tape machines) which has five push-button frequencies. It has the advantage of being battery-powered so it doesn’t cause a ground loop with the amp.

Kalimna

Again, thank you for the replies - all extremely helpful

SubsonicSimpleton

Additional question for the more experienced folks participating in this thread... In recent years there have been a lot of cheap multimeters/compnent testers available on ebay, and I noticed that there are now several low cost digital oscilloscopes appearing like these https://www.ebay.co.uk/itm/2-4-LCD-Display-Fully-Welded-Assembled-Digital-Oscilloscope-With-Probe-UK/223799108078 https://www.ebay.co.uk/itm/100MHz-2-4-LCD-Screen-Digital-Handheld-Oscilloscope-Portable-500MS-s-DIY-L1Q7/202950797688 https://www.ebay.co.uk/itm/Assembled-DSO138-2-4-TFT-Digital-Oscilloscope-Kit-DIY-parts-1Msps-probe/402016533400 Are they likely to be genuinely useful for an aspiring DIYer for pedal/amp work?

ICBM

SubsonicSimpleton said:

Are they likely to be genuinely useful for an aspiring DIYer for pedal/amp work?

I have no experience of them, but from the spec they won't be suitable for valve amp work without a high-voltage probe kit, and maybe not even then. 50V is nowhere near high enough, 500V would be a bare minimum and even that's too low for some amps.

ROOG

I agree with the earlier sentiment and Ozzie video, buy a used analogue oscilloscope first. In my experience, they are easier to use as everything works in real-time, every function has a real control knob or button, and all settings are visible at a glance, they don't have hidden controls like irritating scroll-down menus and twist and push knobs to contend with. My original Tektronix 502a 2ch scope was lovely, but huge and heavy and noisy and hot and no longer calibrated! It had to live on a scope trolly, but it was easy to use and being almost all-tube design, practically impossible to blow up!

 I have recently bought a Rigol DS1054z, 4ch digital storage scope for about £330 when I got it, sure its nice to have a small, but still noisy, accurate scope, but they have economised on user buttons and knobs to keep the small facia workable. Its a pain in the bottom to use!

 A friend of mine has bought an Owon SDS1022 2ch digital storage scope, and because it has less functionality, (not much less) I think its usability is better than mine and for £150 it seems like a good first scope .

 I wouldn't bother with the £25 Amazon or Ebay mini scopes. The one I have seen, worked but 1ch is very limiting, (2 ch are a good thing) and the screen was too small to be practical. Very limited for practical use.

 A signal generator is useful, although nothing beats a good multimeter (both analogue and digital) for usefulness. Also, one of my most used bits of kit, after the DVM is my linear bench power supply.

normula1

I use the Keuwlsoft function generator app as a signal generator for the occasional times I need one.

crunchman

I've got an old oscilloscope that I got from work about 8 years ago when they were having a clearout.  I've not used it in all that time.  It needs new probes, but last time I turned it on the traces on the screen all worked.  It's been in the under stairs cupboard for years.  I can dig it out if you are interested.

Kalimna

Thats extremely kind of you, Crunchman
If you're not too far away, when travel restrictions are lifted, id like to take you up on that offer.

Adam