Author Topic: Recommendation on selecting a used oscilloscope?  (Read 4191 times)

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Offline BillyO

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Re: Recommendation on selecting a used oscilloscope?
« Reply #25 on: June 18, 2024, 03:47:59 pm »
With an old Tek TAS475 selling in working condition for over $500US these days, not buying something new for that price is just silly.  Unless you are getting something in verified working condition for next to nothing, go with something like a Siglent SDS800X HD or a SDS1000X E and get a quality, competent instrument that runs circles around the old girl and come with a warranty.

Of course, maybe you want the challenge of restoring an old beauty and maintaining it and are not really interested in just getting on with a good scope. :-//
Bill  (Currently a Siglent fanboy)
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Offline TomKatt

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Re: Recommendation on selecting a used oscilloscope?
« Reply #26 on: June 18, 2024, 04:15:27 pm »
I love CRO gear and still use my HP 180A regularly for analog work. It was my only scope for many years and did virtually everything I needed.  And despite being nearly as old as I am, it powers up every time and operates flawlessly with a nice, crisp trace.

But since getting my Siglent SDS1104X-E and now the SDS800X HD, there is no way I'd buy an old, used CRO unless I was specifically looking for collectible vintage test gear.  For everyday use, modern gear is more reliable and provides a magnitude greater feature set.
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Online Wallace Gasiewicz

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Re: Recommendation on selecting a used oscilloscope?
« Reply #27 on: June 18, 2024, 04:49:28 pm »
I am with TomKatt and BillyO on this   

Seems to me that the new scopes have so many functions they are in danger of no longer even being called "Scopes"       
I bought an Infinium Agilent Scope used a few years ago and it seems to me that for the price I paid then, you can get a NEW Sigilent with more Functions.   
Please note that I do not have a new Scope and am stuck in Infinium Land.   Maybe not for long though.   

About antique CRT scopes: I really like them.  There are a few things I am aware of that the old Analog CRT scopes do better, but you probably do not need a CRT scope and if you happen to find a use for one, probably a 20 MHz Analog can be found for $20 if and when you think you need it.
 
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Offline Fungus

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Re: Recommendation on selecting a used oscilloscope?
« Reply #28 on: June 18, 2024, 05:08:38 pm »
...with a nice, crisp trace.

That "crisp trace" is because it's hiding things from you, it's like only ever working in "hires" mode on a modern 'scope'.

Compared to their predecessors the traces on the new 12-bit DSOs are plenty "crisp" though.

modern gear is more reliable and provides a magnitude greater feature set.

Two orders.
« Last Edit: June 18, 2024, 05:10:29 pm by Fungus »
 
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Online David Hess

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Re: Recommendation on selecting a used oscilloscope?
« Reply #29 on: June 18, 2024, 07:29:25 pm »
For everyday use, modern gear is more reliable and provides a magnitude greater feature set.

They are an order of magnitude more convenient, but I am not sure about having an order of magnitude greater feature set.  They have all kinds of automated measurements, which save time, but it is an oscilloscope, so I am more interested in what the shape of the wave is.

They are more reliable only because they are new and old oscilloscopes are old, but I doubt current DSOs will operate for as long.  How many modern DSOs have failed because of failed storage or loss of calibration data?  If something breaks, throw it away, and buy a new one.

Things which I would love to do with a DSO which would convince me to buy a new one:

1. Gated RMS noise measurements.  My old Tektronix 2440 DSO does this perfectly.  My analog oscilloscopes also do it perfectly, albeit not as easily.  Some modern DSOs that I have tested simply return the wrong results, maybe from making the RMS measurement on the processed display record?

2. FFT noise density measurements - some very high end DSOs can do this, and as pointed out to me, many R&S models, although I am not clear how far this extends into their lower end models.  I need to do a survey.

3. Frequency and phase response measurements - sorry, the current Bode plot thing is a joke, and not even a good implementation of a swept measurement.  I want the superior FFT version which operates in real time.  Some old DSOs support this, but I will probably have to give up and buy a dedicated low frequency network analyzer for this, which is a shame because it should be so easy on a DSO.  Again some R&S models might support this, and LeCroy high end models.

« Last Edit: June 18, 2024, 07:33:14 pm by David Hess »
 
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Offline BirdManPhil

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Re: Recommendation on selecting a used oscilloscope?
« Reply #30 on: June 18, 2024, 07:35:38 pm »
I just bought a sds804x this morning after a long hard look at available scopes under $1000 and I can't wait for it to arrive
 
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Offline TomKatt

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Re: Recommendation on selecting a used oscilloscope?
« Reply #31 on: June 18, 2024, 08:05:11 pm »
They are an order of magnitude more convenient, but I am not sure about having an order of magnitude greater feature set.  They have all kinds of automated measurements, which save time, but it is an oscilloscope, so I am more interested in what the shape of the wave is.

They are more reliable only because they are new and old oscilloscopes are old, but I doubt current DSOs will operate for as long.  How many modern DSOs have failed because of failed storage or loss of calibration data?  If something breaks, throw it away, and buy a new one.
My HP 180A is evidence that 'good' vintage gear was designed to last longer than equipment built today...  I can't recall the exact year mine was built but I believe it heralds from 1968 or '69.  The only service I've done was to replace the power supply filter caps, which ended up testing fine - I don't think they even needed to be replaced.  I highly doubt any modern equipment will have a service life approaching that - in addition to build quality, their relative simplicity also helps their reliability.  And if it does ever require service, it's often much easier to repair (provided parts are available).  But the problem is that this gear continues to age, so all things being equal they may now have roughly equal service life remaining.
 
And though many people including myself 'look' at waveforms displayed on a CRO, you are often also doing some rough measuring on the graticule - whether that's amplitude or frequency...  Though you may not need the precision offered by modern scope automated measurements, they often are quicker and more accurate than measurements done by eye.
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Offline 2N3055

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Re: Recommendation on selecting a used oscilloscope?
« Reply #32 on: June 18, 2024, 08:15:59 pm »
For everyday use, modern gear is more reliable and provides a magnitude greater feature set.

They are an order of magnitude more convenient, but I am not sure about having an order of magnitude greater feature set.  They have all kinds of automated measurements, which save time, but it is an oscilloscope, so I am more interested in what the shape of the wave is.

They are more reliable only because they are new and old oscilloscopes are old, but I doubt current DSOs will operate for as long.  How many modern DSOs have failed because of failed storage or loss of calibration data?  If something breaks, throw it away, and buy a new one.

Things which I would love to do with a DSO which would convince me to buy a new one:

1. Gated RMS noise measurements.  My old Tektronix 2440 DSO does this perfectly.  My analog oscilloscopes also do it perfectly, albeit not as easily.  Some modern DSOs that I have tested simply return the wrong results, maybe from making the RMS measurement on the processed display record?

2. FFT noise density measurements - some very high end DSOs can do this, and as pointed out to me, many R&S models, although I am not clear how far this extends into their lower end models.  I need to do a survey.

3. Frequency and phase response measurements - sorry, the current Bode plot thing is a joke, and not even a good implementation of a swept measurement.  I want the superior FFT version which operates in real time.  Some old DSOs support this, but I will probably have to give up and buy a dedicated low frequency network analyzer for this, which is a shame because it should be so easy on a DSO.  Again some R&S models might support this, and LeCroy high end models.

First, they don't have to operate that long. New 12 bit 400USD scopes are running circles around many scopes that cost 3000-4000 USD until few years ago. Nobody (except hobby users) wants that old stuff anymore. I would replace it for better, larger screens and much smaller space used on desk alone.
And that old, long running equipment, when was new had comparative cost so high that you could easily buy 20-30 new SDS800XHD for equivalent money today.

It is same as someone told me: That Brymen BM869S looks very good and is much more capable meter than Fluke 87V. But does it have lifetime warranty? My response: "I can buy 3 BM869 for the price of one F87V.. There is your lifetime warranty...."
"Just hard work is not enough - it must be applied sensibly."
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Offline DimitriP

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Re: Recommendation on selecting a used oscilloscope?
« Reply #33 on: June 18, 2024, 08:39:36 pm »
With all the features and capabilities, a 747's  cockpit worth of instrumentation on one screen.....and for some reason no Timebase Ref input !!!!

   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 
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Offline 2N3055

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Re: Recommendation on selecting a used oscilloscope?
« Reply #34 on: June 18, 2024, 10:05:32 pm »
With all the features and capabilities, a 747's  cockpit worth of instrumentation on one screen.....and for some reason no Timebase Ref input !!!!

Are you talking about Keysight 20000 USD MSOX3104T scope?
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Offline DimitriP

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Re: Recommendation on selecting a used oscilloscope?
« Reply #35 on: June 19, 2024, 12:29:06 am »
Naaaahhh....20K don't get you a timebase input , not "high end" enough!   ....28K does !!

https://docs.keysight.com/kkbopen/which-keysight-oscilloscopes-have-a-10-mhz-reference-input-output-589306518.html

 
Quote
Below is a list of Keysight oscilloscopes that include or can include a 10 MHz reference input/output:

    6000 Series
    6000L Series
    7000A Series
    7000B Series
    9000 Series
    54850 Series (Output only)
    80000A Series
    80000B Series
    90000A Series
    90000 X-Series
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 
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