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#1 Wanted Oscilloscope or Advice

Posted: Sun Jan 13, 2019 9:21 pm
by little eddy
Looking to buy an oscilloscope to help with my testing and fault finding.

Does anyone have one they were looking to sell?

I see a few USB ones (particularly Hantek) but there are doubts as to whether some/all of them work with Windows 10. Advice and/or recommendations would be appreciated.

Thanks,

Mike.

#2 Re: Wanted Oscilloscope or Advice

Posted: Mon Jan 14, 2019 1:09 pm
by Mike H
Another important question is, how much do you want to spend? Loads of second-hands on eBay -

Two examples ('buy now' not bidding, I hate bidding): Harmeg 407 (Sheffield), Tenma 72-8240 (Preston), note sellers ask to collect only.

Almost but never quite got around to trying USB types, having got the bandwidth of a real 'scope, I can't see how a PC audio input can match it.

I've got two, both second-hand, the first is a Gould Advance 2-channel, I bought it in 1992-3 -ish, probably 10 years old by then, still working (I think. Not used lately).

The old cathode ray tube ones can be big bulky and heavy mind you. I've also got a second-hand 4-channel Tektronix which is tichy by comparision, and does up to 100 MHz. So what, you may think, but I was surprised how much HF / RF crap can be flying around in audio circuits. :shock: This sort of thing I don''t think a USB PC 'scope will show. NB: the later ones are digital display having a ADC input.

#3 Re: Wanted Oscilloscope or Advice

Posted: Mon Jan 14, 2019 1:45 pm
by Nick
PicoScope 2205A, as a example of a USB connected scope doesn't use a audio card, its got a bandwidth of 25MHz. Think you may be confusing them with the sound card interface I used to use that does use a audio card input, but that's equivalent to a audio analyser not a scope. A analyser needs bit depth whereas a scope doesn't.

Having said that I would never suggest a USB based front end even though the PC will add loads of tricks in terms of analysis that a cheap scope wont have. Reason I would never use it is PC based kit is a pain (IMHO) to use on a work bench.

As said, the big question is budget.

I had to stop using CRT based scopes because my workroom dampness killed their EHT supply. The last CRT scope I had the Tek 465v was a lovely thing, but I have to admit that in all practical ways digital ones are better. 95% of my scope use is a cheap 25Mhz Chinese one I got several years ago now, great value for money. I guess they must appear on the second hand market as well now.

BTW, that Tenma looks identical to the 25Mhz one I used, just with a different name badge.

#4 Re: Wanted Oscilloscope or Advice

Posted: Mon Jan 14, 2019 2:25 pm
by ed
that tenma one that Mike linked looks identical to my 60mhz one with a different badge, same as Nick. I would recommend that type for the price.
My version is a UNI-T and came from a uk distributor with good guarantee. If they look identical on the outside I'm guessing they all come out of the same factory.....

I've had mine for nearly 10 years, moderate use and no complaints at all....

Another consideration is...how often do you use it and what do you use it for....I suppose that determines how much you're going to pay.

#5 Re: Wanted Oscilloscope or Advice

Posted: Mon Jan 14, 2019 3:24 pm
by Nick
That probably means I have had mine for over 10 years, lots of use, no complaints...

#6 Re: Wanted Oscilloscope or Advice

Posted: Mon Jan 14, 2019 3:25 pm
by Nick
What ever you get, make sure you have a set of probes, the price of new probes may come as a shock.

#7 Re: Wanted Oscilloscope or Advice

Posted: Tue Jan 15, 2019 6:29 pm
by Mike H
Nick wrote: Mon Jan 14, 2019 1:45 pm PicoScope 2205A, as a example of a USB connected scope doesn't use a audio card, its got a bandwidth of 25MHz. Think you may be confusing them with the sound card interface I used to use that does use a audio card input,
Didn't know such things existed, so yes I am. :oops:
Having said that I would never suggest a USB based front end even though the PC will add loads of tricks in terms of analysis that a cheap scope wont have. Reason I would never use it is PC based kit is a pain (IMHO) to use on a work bench.
I tend to feel the same way.

#8 Re: Wanted Oscilloscope or Advice

Posted: Fri May 07, 2021 2:16 pm
by Max N
Apologies for resurrecting an old thread, looking for a bit of advice.
Is a 60MHz scope sufficient to rule out oscillation in a valve amp?
MJ talks of using a 300MHz scope to do this. I did buy an old radio on EBay to use for this, but it never turned up. I have a 60MHz scope, so if that is sufficient then I won’t try bidding on another radio!

#9 Re: Wanted Oscilloscope or Advice

Posted: Fri May 07, 2021 2:26 pm
by Nick
I would say it depends on the valves you are using and the frequency they are likely to reach. And/or you are checking the solid state bits wrapped around the valves.

#10 Re: Wanted Oscilloscope or Advice

Posted: Fri May 07, 2021 4:36 pm
by Max N
Nothing particularly high gm on the valve side at the moment (but I would like to be covered for the future)
There is an increasing amount of solid state involved in the current amp, mosfet followers and active loads etc. (I will post an update when I feel I am getting somewhere :) )
I’ve tracked down the reference in MJ, he says ‘if you can guarantee > 100 MHz at your probe tip, use an oscilloscope’
For some reason I remembered a higher bandwidth recommended. I may take my chances with my 60MHz scope, if I can track down the spec on the probes.