EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: MathWizard on February 10, 2021, 08:00:54 am
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I just checked some used prices on a 500MHz scope, and some day I'll get 1, probably some 1980's/90's vintage, and I'm just wondering if there's any to avoid, or to jump at for that matter. I see the usual brands.
They all seemed to get a lot more digital , with a lot more processing going on. Which 500MHz scopes had the most discrete parts, that could be more fixable ?
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I just checked some used prices on a 500MHz scope, and some day I'll get 1, probably some 1980's/90's vintage, and I'm just wondering if there's any to avoid, or to jump at for that matter. I see the usual brands.
They all seemed to get a lot more digital , with a lot more processing going on. Which 500MHz scopes had the most discrete parts, that could be more fixable ?
What is your budget? I'd get a DSO either way and skip the old, analog boat anchors. With a bit of luck you can buy a nice fixer-upper DSO with cosmetic damage for less than US $500. Typically I wouldn't buy anything older than 10 years. Equipment older than that can have all kinds of nasty problems. It does take doing some homework before buying; you'll need to know what the common problems are for certain types of equipment so you can see if the device on offer has a common problem or not and whether it is fixable.
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The problem with that combination of age and bandwidth is you'll be looking at an instrument which is big, heavy, power hungry, and probably on its last legs in terms of lifetime.
One popular range is the Tektronix TDS500-700 series. I first used a 500 series around '99, and I bought a TDS754D shortly after I started my business in 2012.
Fortunately my Tek worked OK, but it put out about 400W of heat, which was no fun at all in a small, south facing lab in summer.
There are plenty of common faults which aren't readily fixable. Electrolytic caps all need replacing on the earlier models, and if leaked electrolyte has damaged the board (as it often does), it can be irreparable. Battery backed memory modules need backing up, replacing and restoring. When the CRT displays or their power supplies die, the only viable fix is an LCD module and they're expensive unless you have the time and inclination to DIY. Memory chips die too, and good luck tracking down which one has failed.
In short, I wouldn't recommend them any more, unless you really want a DIY project. Far better to invest in a more modern scope, IMHO... I'm a lot happier now I have an MSO-X3054A. Their power supplies do fail, but at least it's quite a straightforward and inexpensive replacement when they do.
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Fortunately my Tek worked OK, but it put out about 400W of heat, which was no fun at all in a small, south facing lab in summer.
Yes, the TDS series is the best in the winter, heating+measures all in 1.
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What do you need a 500MHz scope for? What's the application?
500MHz isn't really enough to debug modern memory interfaces, overkill for most serial buses. You might be better off with a decent LA and/or a spectrum analyser.
If you've got spare dosh though I'd try and get an Agilent Infiiiiiiniiiiiium - trouble will more likely be with the PC side of it than the capture IC's. Avoid old LeCroy's they are like Alfa Romeo's. YMMV.
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I am extremely happy with my HP 54542A. I paid something over $200 a few years ago and it's been very good.
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Why get something so old rather then getting a cheap Chinese unit? You may be much further ahead.
I have a few old LeCroy scopes from that era. I gave one away but then a while back a friend of mine gave me another one. These are not something I would recommend the average non-technical beginner go out and buy. A couple of my repair videos, show why.
The ones I have from the 2000 era are much better but again, not something I would recommend for a beginner.
https://www.youtube.com/watch?v=WXFoAAL7hxo (https://www.youtube.com/watch?v=WXFoAAL7hxo)
https://www.youtube.com/watch?v=7SByDsNaYiA (https://www.youtube.com/watch?v=7SByDsNaYiA)
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I just checked some used prices on a 500MHz scope, and some day I'll get 1, probably some 1980's/90's vintage, and I'm just wondering if there's any to avoid, or to jump at for that matter. I see the usual brands.
They all seemed to get a lot more digital , with a lot more processing going on. Which 500MHz scopes had the most discrete parts, that could be more fixable ?
What is your budget?
Exactly. Always budget. Due to software keys that can easily increase the bandwidth, a 500MHz more modern oscilloscope can be had for a somewhat reasonable price (about US$1800 on Rigol's clearance bin (https://www.rigolna.com/clearance/) DS4012 hacked) or, if you can live with 350MHz, the options are much wider: Rigol MSO5000, Siglent SDS2000X+.
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I just checked some used prices on a 500MHz scope, and some day I'll get 1, probably some 1980's/90's vintage, and I'm just wondering if there's any to avoid, or to jump at for that matter. I see the usual brands.
They all seemed to get a lot more digital , with a lot more processing going on. Which 500MHz scopes had the most discrete parts, that could be more fixable ?
What is your budget?
Don't forget to include the cost of appropriate scope probes in the budget, where "appropriate" depends on what you are going to be measuring.
"Appropriate" excludes traditional 10Mohm *10 probes, since they aren't 10Mohm at 500MHz.
I second the suggestion that you might also consider a logic analyser or protocol analyser.
If you want to look at RF signals, you should consider a dedicated spectrum analyser, and be aware of the limitations of scopes+FFT.
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Ok thanks, I don't really need a faster scope for anything in particular atm, but I just more zoom, I want to see those fast edges, I'm tired of stopping at when I see my local 99MHz radio station.
It would probably take too long to afford anything new or 10yrs old. I'd really like a 1GHz scope, IDK, maybe I should skip the 500Mhz scope, but the cheapest of them is pretty affordable.
I won't be using it that much, if I got an old 1 in good shape, hopefully it would last a long time.
Down the road I'll be looking for a cheap spectrum analyzer, for now I can use the FFT on my Siglent scope.
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Ok thanks, I don't really need a faster scope for anything in particular atm, but I just more zoom, I want to see those fast edges, I
Make sure you understand how probes interact with your circuit at those speeds.
See the references at https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/
See some easy examples at https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/ https://entertaininghacks.wordpress.com/2016/09/17/scope-probe-accessory-higher-frequency-results/ https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/
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I would wait until you have a need for one.
Ted Yapo on his custom sampling scope.
https://www.youtube.com/watch?v=99u53V7uDFY (https://www.youtube.com/watch?v=99u53V7uDFY)