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Older high-end vs new mid-range scopes.

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cyr:
I have been looking for a while at getting a decent DSO (upgrading from a DS1102E), my budget will just about stretch to something like the Rigol DS4024 (~3000 USD).

I wonder though if there are any decent used options at the same price range (or below) worth considering. Quickly looking around ebay I found Agilent Infiniiums, some LeCroys, TDS784, TDS5000. "Floppy-era" 4ch stuff, 500-1000MHz, 2-8Gs/s, 1-16Mpts.

The main advantage with the older scopes seems to be that I could get around 1GHz of bandwidth instead of 200M. There are some obvious disadvantages, like the size/weight and fan noise of these old beasts and of course the fact that they are used and without any warranty.

I do play around a bit with some pretty high speed logic (FPGA interface to various stuff) so I think the higher bandwidth might be useful sometimes, along with features like graduated persistance display and histograms which I believe most of those scopes have but the Rigol is missing. I have no experience with any of those scopes though, I have no idea how good they are in real use. Would I be crazy to go for one of the old ones?

EEVblog:
1GHz bandwidth is great, but pretty useless without the right high speed FET probes, and they can cost more than the scope!
500MHz is usually more than enough.

Check out Agilent Certiprime ebay store from time to time:
http://stores.ebay.com.au/Agilent-Remarketing-Solutions-Store/Oscilloscopes-/_i.html?_fsub=3420071011&_sid=869664151&_trksid=p4634.c0.m322
Fully calibrated and warranted by Agilent.

A good Agilent 6000 series unit would be a great buy, or any of the Infiniiums.

Dave.

AndyC_772:
I agree with Dave on the bandwidth, 500 MHz is about the upper limit for a passive probe, and for that reason I'd regard it as a sensible upper limit for a general purpose bench scope. If you need anything faster then you'll already have a specific application in mind and you'll know how much bandwidth that application requires. Expect to pay a lot for active probes.

I have a Tek TDS754D which is 4 chans, 500 MHz and has a proper intensity graded display - albeit an early implementation which you have to enable manually and in which all channels become the same colour. The UI is a little bit sluggish, and if you want to capture waveforms from it then you'll need a floppy disc drive, but it's still a perfectly usable and capable piece of equipment. It would certainly be a major step up from a 'toy' scope like the 1102.

The Tek TDS5xx/6xx/7xx series are plentiful enough on the s/h market and you can get them from dealers with warranties, though I'm inclined to feel they're overpriced in many cases. Earlier models (prior to the 'D' suffix variants) contain electrolytic capacitors which leak corrosive electrolyte and cause all sorts of problems, so I'd suggest getting either a 'D' or an earlier one which has been refurbished, had the caps replaced and any damage repaired. Avoid anything that fails the start-up self test; many of them have faulty acquisition boards where the caps have leaked.

nctnico:
When it comes to the TDS500, 600 and 700 series the capacitor problems depend on the age of the scope. The early models from around 1992 have leaking capacitors. Older models >1995 have better capacitors or use ceramics. One or two errors mean the capacitors are leaking but there problably is no real damage yet. There are a couple of electrolytics on the  PLL board which fails due to the capacitors going out of spec. I have restored a TDS644A and a TDS544A without much problems. My TDS510A and TDS744A which are from around 1995 show no signs of leaking capacitors.

Wuerstchenhund:

--- Quote from: cyr on February 28, 2013, 11:16:37 am ---I have been looking for a while at getting a decent DSO (upgrading from a DS1102E), my budget will just about stretch to something like the Rigol DS4024 (~3000 USD).

I wonder though if there are any decent used options at the same price range (or below) worth considering. Quickly looking around ebay I found Agilent Infiniiums, some LeCroys, TDS784, TDS5000. "Floppy-era" 4ch stuff, 500-1000MHz, 2-8Gs/s, 1-16Mpts.
--- End quote ---

Good idea. I personally would take an older scope from HP/Agilent, LeCroy or Tektronix any day.


--- Quote ---The main advantage with the older scopes seems to be that I could get around 1GHz of bandwidth instead of 200M.
--- End quote ---

As others said, forget 1GHz unless you really need the bandwidth and are prepared to shell out for an appropriate active probe. More than 500MHz is a waste for general purpose use.


--- Quote ---There are some obvious disadvantages, like the size/weight and fan noise of these old beasts and of course the fact that they are used and without any warranty.
--- End quote ---

Right, but then if you buy from a Chinese seller your warranty may be worth nothing (especially a problem with Rigol), and the warranty doesn't necessarily cover firmware or hardware bugs.


--- Quote ---I do play around a bit with some pretty high speed logic (FPGA interface to various stuff) so I think the higher bandwidth might be useful sometimes, along with features like graduated persistance display and histograms which I believe most of those scopes have but the Rigol is missing. I have no experience with any of those scopes though, I have no idea how good they are in real use. Would I be crazy to go for one of the old ones?

--- End quote ---

No, but you have to be realistic about what you want (see the point about the bandwidth). Many older scopes come with CRT and may show some burn-in marks. They also lack USB or Ethernet.

On the other side, a 2nd hand scope from the big names gives you a tool for professional use.

On what scope to get, have a look at the LeCroy Waverunner 2 series (LTxxx). They come with a wide range of signal analyzing tools (especially if you find one which has the additional software options) which you won't find in other scopes. A LT374 (500MHz 4Ch 4GSa/s) might be worth a look, you should be able to find one in good condition for your budget. If you can do with less bandwidth/sample rate, look at the LT264 (350MHz 4Ch 1GSa/s) as well.

As to the Agilent Infiniiums, I'be be careful with them. Early models run Windows95 and are prone to crashing in the worst possible moments. The later variants running Windows 2000 or XP are much more reliable, but also much more expensive.

And quite frankly, I'd also avoid the Tek TDS500/600/700 Series, unless it has to be really cheap. They were good scopes in their days but the screen is small and the UI slow, and there's not too much in terms of signal analysis. The TDS5000 is a much better choice.

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