DSO Reliability

[G0HZU]

Congats on the find and hopefully a full repair.
So often another scope is needed to repair another. 
Nothing like keeping your eyes open though for the obvious.

Good call to proceed with the purchase of a DSO, you will marvell at their capabilities.

If what I was told about the limited usefulness of the FFT function in these DSOs is true, I must admit that some of my interest has dissipated.  However, who knows, maybe the spectrum analyzer aspect is better now....

I think the FFT feature on my old Tek TDS2012 can be useful. It does require a degree of sympathy for its limitations but you can do useful stuff with the FFT feature that is impossible on the analogue 465.

I've used it to look at two tone IMD levels from an RF amplifier or from a receiver/detector demod output and it can be used to look at the frequency response of noise. It's pretty quick when used for all of the above tasks as long as you don't expect too much in the way of precision and you can learn to spot and ignore any unwanted alias terms that creep onscreen. Of course, for some of the above AF based tasks it can be outclassed by a PC soundcard but sometimes it's quicker to just press the FFT button on the scope and make a casual measurement...

[TunerSandwich]

to me the biggest problem with modern DSO's is the lack of external clock sync and tools to time align with other acquisition tools.....that baffles me beyond any of the other potential "problems" with these tools...

Not sure what scopes you are looking at specifically, but only the very base low end scopes do not provide a 10Mhz ref in (sometimes out as well) and also a trigger output. Using these two connections should be sufficient to synchronize with other test gear.

I am talking about clock synch, not a ref....sampling clock =)

The latency across connections and lack of resolution in triggers makes it impossible to get sample accurate lock across multiple units.

Even using a distribution amp and precisely matched cables doesn't allow for total GenLock.....the triggers are just to coarse.

Yokogawa seems to get it though....a lot of their gear does have true clock in and out, with delays inline to deskew....good stuff

[TunerSandwich]

to me the biggest problem with modern DSO's is the lack of external clock sync and tools to time align with other acquisition tools.....that baffles me beyond any of the other potential "problems" with these tools...

Not sure what scopes you are looking at specifically, but only the very base low end scopes do not provide a 10Mhz ref in (sometimes out as well) and also a trigger output. Using these two connections should be sufficient to synchronize with other test gear.

He might be referring an external sample clock input.  I have a couple of old DSOs which support this.

As far as the trigger outputs on modern DSOs, they seem to have a lot of latency and/or jitter compared to older DSOs which use analog triggering.

I know some Yokogawa units have the true clock in (no re-sampling or modification to the input).....would love to know what other units support this feature.

The trig outs are def not usable to do true time correlated sync....drift is pretty bad....

Hopefully someday there will be a test set that can use a true sample accurate lock (of time base)....granted we would need a nice distro amp and cables to handle that, but it's an appealing prospect.  It would be nice to do multi-domain analysis on dedicate boxes, all locked up.  Rather than one box that tries to "do it all". 

The Tek MDO is a good example of why it's just not practical to do everything in one box and on one screen.....

[Wuerstchenhund]

I know some Yokogawa units have the true clock in (no re-sampling or modification to the input).....would love to know what other units support this feature.

From LeCroy at least the WavePro 7000(A) Series and later offer ext. sample clock input as well, although at the moment I'm not sure if this is standard or part of one of the options.

It might be that some of the other LeCroy scopes (i.e. WaveRunner Series) support it as well, but I'd have to check.

[TunerSandwich]

I know some Yokogawa units have the true clock in (no re-sampling or modification to the input).....would love to know what other units support this feature.

From LeCroy at least the WavePro 7000(A) Series and later offer ext. sample clock input as well, although at the moment I'm not sure if this is standard or part of one of the options.

It might be that some of the other LeCroy scopes (i.e. WaveRunner Series) support it as well, but I'd have to check.

I know the labmasters support true sample clock (ext) ref.

BTW I wound up buying that loaded 64MXi....so i will do some testing on it's external input and see if it is time aligned, to sample accuracy.....would be very cool if it is.  Looking forward to playing with the new tool and seeing just what it can do. 

We had talked about processor upgrades in the other thread.  Do you think the same processors will apply to the MXi? 

If this unit works out, I might just replace the other scopes with some new LeCroy units.  They are very compelling tools.  I had used them in the past, and liked them, but never got very deep into what they can really do.  Our conversation in the prior threads, has me really curious if they can live up to their claims....esp. the DEVkit and more advanced feature sets....

[Wuerstchenhund]

I know the labmasters support true sample clock (ext) ref.

Indeed. If I come around I can check my 64Xi and LT264M tonight.

Update: Checked my  LT264M, and as expected even this old scope offers external sample clock input (TTL, ECL and 0V, 50ohms or 1Mohms switchable).

BTW I wound up buying that loaded 64MXi....so i will do some testing on it's external input and see if it is time aligned, to sample accuracy.....would be very cool if it is.  Looking forward to playing with the new tool and seeing just what it can do. 

Congratulations! It's a very good scope, and certainly a very good deal you got there.

We had talked about processor upgrades in the other thread.  Do you think the same processors will apply to the MXi?

The difference between Xi and MXi is the presence of the L-Bus (LeCroy Bus) interface on the latter, the rest is the same. So yes, the MXi will take Socket479 Celeron-M and Pentium-M processors, and a single full size DIMM of DDR1 SDRAM.

I found that the 1.3GHz Celeron that comes with these units wasn't the best choice by LeCroy, mostly because of its tiny cache (512k). As on X-Stream scopes everything happens within the CPU cache, the performance benefits a lot from larger cache. My 64Xi got a 1.8GHz Pentium-M with 2MB Cache and a 1GB RAM upgrade, and the difference was clearly noticable (the scope also does feel a lot snappier now).

The (M)Xi also has an integrated hard drive (a slow Toshiba 4200rpm 2.5" EIDE drive). I had replaced that with a new 5400rpm Seagate drive and a SATA bridge. I did try several SSDs (EIDE and SATA) but all of them showed some data corruption, probably because of the specific setup (44pin cable which does not support UDMA66 or faster modes), so I opted for a new 2.5" SATA drive which works fine.

BTW: the first thing you should do when you get your scope is to save the hidden \calibration folder on the D: drive. It contains the factory calibration and is crucial. Make sure you have backups, don't loose it!

If this unit works out, I might just replace the other scopes with some new LeCroy units.  They are very compelling tools.  I had used them in the past, and liked them, but never got very deep into what they can really do.  Our conversation in the prior threads, has me really curious if they can live up to their claims....esp. the DEVkit and more advanced feature sets....

They do make great scopes. Just make sure you stay away from their WaveAce (cheap Siglent rebadges) and WaveJet (Iwatsu rebadges with outdated specs) Series. Always go for a WaveSurfer or higher.

BTW: it would be great if you could do a review of your 64MXi, especially of things like PMA1 and the SPECTRUM option (maybe you could show the FFT as well, just as a comparison). I'm sure many people would be interested to see what a modern advanced scope can do.

[TunerSandwich]

I am considering an HDO8000.  The extra resolution seems VERY beneficial for the type of work I do. 

Thanks for the tips on processor, HDD and potential mistakes I could make.  I remember we talked about cloning the drive and hidden volumes.  I will try to use shadow protect to do a full image, and then see if I can clone the drive using some of my favorite utilities.  So I will look into that Pentium-M and some RAM upgrades (might not really need them?)

I plan on doing full reviews and tear-downs of the unit I got.  There is a real lack of information and support on the net.  I think it would possibly help some folks to know more about these scopes, and how far ahead of the curve they were/are. 

My plan was to focus on PMA, Spectrum and the protocol analysis functions (the part i am most skeptical about).  I will also see if I can get a good time aligned signal across a few units, using an external sample clock ref.  Obviously we don't get a timebase sync input, so the sample clock might not be as useful, without that.  I noticed Yokogawa gives you two sync ref inputs.  One for sample clock and another for a timebase.  This is the typical way digital sync loops work.  For example in high end audio production and video production gear we get BOTH word clock i/o AND SMPTE time code.  I am hoping there is the possibility of a similar scenario here.  If not we can use some external generators to get some sharp clips into the waveforms, and then capture, export and time align later (the way we currently do it). 

I assume from your experience, there is no SATA on board the MOBO?  I have a few tricks to try and remedy that, but need to clone those volumes first.  Would hate to turn this scope into a doorstop.....

[J-D-H]

Maybe so, but my experience with dome switch computer keyboards has been less than stellar.  Of course this may be an apples to orange comparison, but I'd still rather see more robust hardware (for a few bucks more, of course).

You don't have a choice. All modern test equipment uses the same kind of switches, from the cheapest DSO, to the most expensive exotic comms analysers. Some examples of these switches are a bit better made, but they are all pretty similar. The biggest problem comes when heavy units need to be moved. Its very common for one or two of the switches to take a big enough hit from the mover that you end up with damage - often a switch ripped right out of the membrane sheet. These can be very costly to fix. You can't go to anyone but the original source for a replacement membrane, and they can charge whatever they like. A short time after production stops the supply of suitable spares will dry up. These are the real issues with membrane switches, not general wear and tear.

As for computer keyboards, your view might be distorted. If you have trouble and open up a keyboard you will find it is a membrane type. However, almost all the ones which don't give trouble are also the membrane type. Only a small quantity of specialised keyboards, like those available from pckeyboard.com, are not membrane ones.

I use computer keyboards which incorporate great mechanical switches made by Cherry.  Beautiful feel, long life, and while more costly than rubber dome style products, they don't break the bank.  However if all modern DSOs use the same switch types, of course this falls out of my decision tree.  Thanks for the input re this....

[J-D-H]

If what I was told about the limited usefulness of the FFT function in these DSOs is true, I must admit that some of my interest has dissipated.  However, who knows, maybe the spectrum analyzer aspect is better now....

I'm not sure what you were hoping to get from the FFT engines.

There is a pretty simple way to organize the "useful range" of an FFT: your max frequency will be set by your sample rate, your frequency bins will be set by the maximum window. (Rough approximation)

Example: I have my scope set to 100us/div, with 10 divisions width. My sample rate is set to 800ps/pt (1.25GSPS). Fmax will be 1/2 your sample rate (625MHz) and the bin width will be 1/(10*100uS) = 1kHz which will also set the minimum frequency of the window. Processing 1,250,000 points will take a big chunk of time too.

Dynamic range will also be crap. Most of the 8-Bit ADCs might get 6 bits ENOB. Even with all of the other sampling tricks you can pull, you won't have a very good "noise floor" with the FFT.

Call me a curmudgeon, but I'd be more concerned about having a scope that is primarily a scope and not a gimmick box that happened to start life as a scope.

I was told that the freq span in FFT mode would always effectively be equal to the bandwidth of the scope.  So in my case, the span would be 100 MHz -- not very useful if I'm looking for the harmonic content of some audio device.  Furthermore, I heard that the spectrum display is not calibrated either in freq or in amplitude.  Sounds like this may not have been completely accurate -- but close?

[J-D-H]

He also described how these modern DSOs implement the FFT spectrum analyzer function (or at least how many of them used to do it).  I was blown away when he said most have no calibration for this function -- IOW, no freq scale.  He also said they have no means to adjust the freq scale.  It sounded like he was describing more of a toy than anything else when it comes to the FFT aspect.  He did mention that they get better all the time, so that it's possible that the latest units might have a more worthwhile and useful FFT capability -- but I suppose he wasn't sure of the current state of the art.

The issue here may be that many DSOs do not apply the correction factors needed to produce a calibrated output making them difficult to use in place of a spectrum analyser.  This EDN article discusses it:

http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/DSOs-and-noise-
http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/2/DSOs-and-noise-

Thanks for this....

[J-D-H]

If what I was told about the limited usefulness of the FFT function in these DSOs is true, I must admit that some of my interest has dissipated.  However, who knows, maybe the spectrum analyzer aspect is better now....

You get what you pay for. The Rigols all have very poor FFT which only uses a few hundred points, and I'd assume (haven't checked if the figure is out there) that Siglent SDS1000/2000 scopes use similar low numbers which they do because their processing is dog slow.

Really old DSOs often use something around the 10kpts mark which, while being much better than modern day Rigols, is still too little, and scopes like the TDS700 Series (which at that time was their highend model) use somewhere around the 100kpts which is where FFT starts to become actually useful, but since these scopes are really old (close to 20 years) and their processing is very slow as well.

Honestly, if you want good FFT then you should have a look at a LeCroy scope. Even the now roughly 20 yrs old 9300 Series could use up to 6Mpts for FFT (although of course the processing is also slow by today's standard due to their age). But the later scopes (i.e. WaveRunner LT) have much faster processing, and with the EMM or WAVA option use the full available sample memory for FFT. They also show signal phase, which most scopes don't.

A Spectrum Analyzer is of course much better for analyzing the RF spectrum than any scope, but you do pay a lot for that. FFT in a good(!) scope however can often be more than good enough.

With my limited home shop budget, it sounds like I need to revisit to used market.  Thamks for the tips.

[J-D-H]

Congats on the find and hopefully a full repair.
So often another scope is needed to repair another. 
Nothing like keeping your eyes open though for the obvious.

Good call to proceed with the purchase of a DSO, you will marvell at their capabilities.

If what I was told about the limited usefulness of the FFT function in these DSOs is true, I must admit that some of my interest has dissipated.  However, who knows, maybe the spectrum analyzer aspect is better now....

I think the FFT feature on my old Tek TDS2012 can be useful. It does require a degree of sympathy for its limitations but you can do useful stuff with the FFT feature that is impossible on the analogue 465.

I've used it to look at two tone IMD levels from an RF amplifier or from a receiver/detector demod output and it can be used to look at the frequency response of noise. It's pretty quick when used for all of the above tasks as long as you don't expect too much in the way of precision and you can learn to spot and ignore any unwanted alias terms that creep onscreen. Of course, for some of the above AF based tasks it can be outclassed by a PC soundcard but sometimes it's quicker to just press the FFT button on the scope and make a casual measurement...

This brings up the idea of a laptop based instrument setup, whether it be for time or freq domain measurements.  I have never owned one, never messed with one, but maybe this would be a viable option for my home shop......

[Wuerstchenhund]

I am considering an HDO8000.  The extra resolution seems VERY beneficial for the type of work I do. 

The HDO8k is great, and I guess 8 channels might be a benefit for your work, too.

Thanks for the tips on processor, HDD and potential mistakes I could make.  I remember we talked about cloning the drive and hidden volumes.  I will try to use shadow protect to do a full image, and then see if I can clone the drive using some of my favorite utilities.  So I will look into that Pentium-M and some RAM upgrades (might not really need them?)

You don't need them, the scope is fine as it is. It does help if you do a lot of processing, though.

I wouldn't bother cloning the original drive, there's nothing special on it (aside from the calibration data of course). Just save the cal data and you're safe. If required just use a generic Windows XP Pro CD and install from there, and then download software 7.3.0.9 and 7.4.0.9 from the LeCroy site.

I plan on doing full reviews and tear-downs of the unit I got.  There is a real lack of information and support on the net.  I think it would possibly help some folks to know more about these scopes, and how far ahead of the curve they were/are. 

Nice! Just a word of warning, though: the connectors which connect the Front End to the Aquisition Board are really very fragile. They are the only real weak point in these scopes. If you ever find that a channel only shows noise or a very distorted signal, and at the same time the trace jumps back into the middle after turning the vertical offset, then you should check these connectors. When this happens they usually only need resoldering, but in some cases they need replacing.

I assume from your experience, there is no SATA on board the MOBO?  I have a few tricks to try and remedy that, but need to clone those volumes first.  Would hate to turn this scope into a doorstop.....

No SATA, just IDE. It's also 44pin, which means the cable is 40 conductor (there are no 80 conductor 44pin cables as far as I know) which means the UDMA133 chipset is limited to UDMA33 only. But that isn't much of a problem for a scope.

Cheap Chinese 44pin EIDE to SATA bridges work fine (just be careful with the space), and allow the use of modern 2.5" SATA drives. You could also use one of those SSHDs (hard drive with SSD cache), although I doubt it will bring any noticable benefit (on the other hand, these drives are dirt cheap). Just forget about SSDs in this scope.

CPU, RAM and hard drive are the only alterations I would consider doing on such a scope, though. Don't forget that if you break something LeCroy will fix it, but it probably won't be cheap.

[TunerSandwich]

I am considering an HDO8000.  The extra resolution seems VERY beneficial for the type of work I do. 

The HDO8k is great, and I guess 8 channels might be a benefit for your work, too.

Thanks for the tips on processor, HDD and potential mistakes I could make.  I remember we talked about cloning the drive and hidden volumes.  I will try to use shadow protect to do a full image, and then see if I can clone the drive using some of my favorite utilities.  So I will look into that Pentium-M and some RAM upgrades (might not really need them?)

You don't need them, the scope is fine as it is. It does help if you do a lot of processing, though.

I wouldn't bother cloning the original drive, there's nothing special on it (aside from the calibration data of course). Just save the cal data and you're safe. If required just use a generic Windows XP Pro CD and install from there, and then download software 7.3.0.9 and 7.4.0.9 from the LeCroy site.

I plan on doing full reviews and tear-downs of the unit I got.  There is a real lack of information and support on the net.  I think it would possibly help some folks to know more about these scopes, and how far ahead of the curve they were/are. 

Nice! Just a word of warning, though: the connectors which connect the Front End to the Aquisition Board are really very fragile. They are the only real weak point in these scopes. If you ever find that a channel only shows noise or a very distorted signal, and at the same time the trace jumps back into the middle after turning the vertical offset, then you should check these connectors. When this happens they usually only need resoldering, but in some cases they need replacing.

I assume from your experience, there is no SATA on board the MOBO?  I have a few tricks to try and remedy that, but need to clone those volumes first.  Would hate to turn this scope into a doorstop.....

No SATA, just IDE. It's also 44pin, which means the cable is 40 conductor (there are no 80 conductor 44pin cables as far as I know) which means the UDMA133 chipset is limited to UDMA33 only. But that isn't much of a problem for a scope.

Cheap Chinese 44pin EIDE to SATA bridges work fine (just be careful with the space), and allow the use of modern 2.5" SATA drives. You could also use one of those SSHDs (hard drive with SSD cache), although I doubt it will bring any noticable benefit (on the other hand, these drives are dirt cheap). Just forget about SSDs in this scope.

CPU, RAM and hard drive are the only alterations I would consider doing on such a scope, though. Don't forget that if you break something LeCroy will fix it, but it probably won't be cheap.

Thanks again for all of your insights.

I might not mess with the unit at all.  If it works fine, no need =)

I will clone the entire volume as a safety precaution.  I did notice LeCroy is still giving limited support on the MXi. 

I agree that the SSD isn't going to really show much benefit, across an old bus master.  No point, and the potential issue of corruption we had discussed (XP has no garbage collertion/trim and also will try to initiate defragmentation).  Those items can all be dealt with and "turned off", but it's hardly worth the hassle, to see no benefit.

I will try and make a few cables here.  I if am successful, i would be happy to send you one (token of appreciation for all of your help and effort). 

RAM u/g seems like a no brainer.  I have a few stick of old stuff laying around. 

Are the connections in the front surface mount or flying leads?  Hope they aren't aging flat flex. 

[Wuerstchenhund]

With my limited home shop budget, it sounds like I need to revisit to used market.  Thamks for the tips.

Think about what you really want from a scope, and then have a look at the 2nd hand market. There are lots of attractive deals out there, even for newer scopes (you don't have to settle for a boat anchor with a fish bowl).

In terms of what to buy, Agilent and (some, not all!) Tek is usually a safe bet but prices are higher (as they're more sought after than other brands) and depending what you want you get average features at best.

But if you want advanced FFT and signal analysis then definitely look at LeCroy (not WaveSurfer/WaveAce models, though!). They really do make the most advanced scopes, and because most people only think "Tek" and "Agilent" when thinking about scopes prices are often lower. Another benefit is that the probe interface is mostly unchanged since the 9300 Series from 1994.

[Wuerstchenhund]

Thanks again for all of your insights.

You're welcome! It's a nice change from the strong Rigol/Siglent/Hantek focus in this forum 

I might not mess with the unit at all.  If it works fine, no need =)

I will clone the entire volume as a safety precaution.  I did notice LeCroy is still giving limited support on the MXi. 

The MXi went out of sale in 2009, which means it is still fully supported until 2016. After that there is limited support based on "best effort", which means that some boards might no longer be available as spare part and will be repaired instead.

Realistically I'd expect that you'll be able to get this thing repaired until at least 2020. LeCroy still repairs the 9300 Series, and this went out of sale around 1998.

I agree that the SSD isn't going to really show much benefit, across an old bus master.  No point, and the potential issue of corruption we had discussed (XP has no garbage collertion/trim and also will try to initiate defragmentation).  Those items can all be dealt with and "turned off", but it's hardly worth the hassle, to see no benefit.

I will try and make a few cables here.  I if am successful, i would be happy to send you one (token of appreciation for all of your help and effort). 

Thanks for the offer, but I guess shipping is going to kill it.

Just thank me by doing a review of your scope 

Are the connections in the front surface mount or flying leads?  Hope they aren't aging flat flex.

The Front End connectors are SMD mounted hard connectors. I guess they could be replaced with some good flex cables should they ever fail, though.

[TunerSandwich]

Thanks again for all of your insights.

You're welcome! It's a nice change from the strong Rigol/Siglent/Hantek focus in this forum 

I might not mess with the unit at all.  If it works fine, no need =)

I will clone the entire volume as a safety precaution.  I did notice LeCroy is still giving limited support on the MXi. 

The MXi went out of sale in 2009, which means it is still fully supported until 2016. After that there is limited support based on "best effort", which means that some boards might no longer be available as spare part and will be repaired instead.

Realistically I'd expect that you'll be able to get this thing repaired until at least 2020. LeCroy still repairs the 9300 Series, and this went out of sale around 1998.

I agree that the SSD isn't going to really show much benefit, across an old bus master.  No point, and the potential issue of corruption we had discussed (XP has no garbage collertion/trim and also will try to initiate defragmentation).  Those items can all be dealt with and "turned off", but it's hardly worth the hassle, to see no benefit.

I will try and make a few cables here.  I if am successful, i would be happy to send you one (token of appreciation for all of your help and effort). 

Thanks for the offer, but I guess shipping is going to kill it.

Just thank me by doing a review of your scope 

Are the connections in the front surface mount or flying leads?  Hope they aren't aging flat flex.

The Front End connectors are SMD mounted hard connectors. I guess they could be replaced with some good flex cables should they ever fail, though.

hmmm yes the SMD connections sound bearish....might try to get some train relief on there and see how fragile they are, before I go mucking about inside the scope

I'm still happy with the ds2000A-s.....the low noise front end makes it useful as a pseudo replacement for the old TEK....when general ripple measurements are needed.....however it never did serve much use (for me) beyond that.....like I was saying earlier, I might ditch some other scopes here for an HDO8000....what a beast.  Going to try and get a demo unit out here. 

I have bulk mail at my business, so if I can make some cables and figure something out (and the shipping isn't ridiculous) I would be happy to get some over to you (if you think it';s even worth the hassle).

I will most def do some reviews on various packages (as soon as the current probes are sourced, and an ms-500).  I found a real lack of information on this wonderful lab tool online.....it might help some folks down the road, to see an in depth review of some unique features.

[tautech]

Maybe so, but my experience with dome switch computer keyboards has been less than stellar.  Of course this may be an apples to orange comparison, but I'd still rather see more robust hardware (for a few bucks more, of course).

You don't have a choice. All modern test equipment uses the same kind of switches, from the cheapest DSO, to the most expensive exotic comms analysers. Some examples of these switches are a bit better made, but they are all pretty similar. The biggest problem comes when heavy units need to be moved. Its very common for one or two of the switches to take a big enough hit from the mover that you end up with damage - often a switch ripped right out of the membrane sheet. These can be very costly to fix. You can't go to anyone but the original source for a replacement membrane, and they can charge whatever they like. A short time after production stops the supply of suitable spares will dry up. These are the real issues with membrane switches, not general wear and tear.

As for computer keyboards, your view might be distorted. If you have trouble and open up a keyboard you will find it is a membrane type. However, almost all the ones which don't give trouble are also the membrane type. Only a small quantity of specialised keyboards, like those available from pckeyboard.com, are not membrane ones.

I use computer keyboards which incorporate great mechanical switches made by Cherry.  Beautiful feel, long life, and while more costly than rubber dome style products, they don't break the bank.  However if all modern DSOs use the same switch types, of course this falls out of my decision tree.  Thanks for the input re this....

With my limited home shop budget, it sounds like I need to revisit to used market.  Thamks for the tips.

As I have stated before, failures with DSO membrane keypads have been non-existant IME.

However I have repaired many CRO's I have owned in the past and consider their reliability to be much more questionable.
The HV portions for the CRT and the CRT plate output circuits in particular.
I qualify this with mention of the humid climate here in NZ, that may have a bearing on CRT HV leakage and or PCB corrosion.
These areas are electrically stressed by design and with age they are prone to failure.

DSO's by comparison have been highly reliable IME, no failures in any I have supplied ASFAIK.
I was given a 20 yr old TDS210 with no backlight that turned out to have a failed backlight oscillator, needing only a 30c cap for a full repair.

This thread has confirmed my beleif that DSO's in general have been very reliable to date, and it will be interesting as more decades slip by to see if this remains the case.

J-D-H, it seems FFT performance is of importance to you and a new thread on this matter may be worthy of thought.

[MarkL]

He also described how these modern DSOs implement the FFT spectrum analyzer function (or at least how many of them used to do it).  I was blown away when he said most have no calibration for this function -- IOW, no freq scale.  He also said they have no means to adjust the freq scale.  It sounded like he was describing more of a toy than anything else when it comes to the FFT aspect.  He did mention that they get better all the time, so that it's possible that the latest units might have a more worthwhile and useful FFT capability -- but I suppose he wasn't sure of the current state of the art.

The issue here may be that many DSOs do not apply the correction factors needed to produce a calibrated output making them difficult to use in place of a spectrum analyser.  This EDN article discusses it:

http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/DSOs-and-noise-
http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/2/DSOs-and-noise-

Thanks for this....

This article is referring to measuring noise with a DSO.  Is that your application?

A DSO will display FFT peaks calibrated in both frequency and amplitude, and the frequency scale (you mean span & center?) is adjustable.   To get the best results you have to select an appropriate sampling speed in the time domain for the signal of interest, and you need to be cognizant of FFT aliasing issues.

What does he mean by it's "not calibrated"?

[David Hess]

He also described how these modern DSOs implement the FFT spectrum analyzer function (or at least how many of them used to do it).  I was blown away when he said most have no calibration for this function -- IOW, no freq scale.  He also said they have no means to adjust the freq scale.  It sounded like he was describing more of a toy than anything else when it comes to the FFT aspect.  He did mention that they get better all the time, so that it's possible that the latest units might have a more worthwhile and useful FFT capability -- but I suppose he wasn't sure of the current state of the art.

The issue here may be that many DSOs do not apply the correction factors needed to produce a calibrated output making them difficult to use in place of a spectrum analyser.  This EDN article discusses it:

http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/DSOs-and-noise-
http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4427466/2/DSOs-and-noise-

Thanks for this....

This article is referring to measuring noise with a DSO.  Is that your application?

A DSO will display FFT peaks calibrated in both frequency and amplitude, and the frequency scale (you mean span & center?) is adjustable.   To get the best results you have to select an appropriate sampling speed in the time domain for the signal of interest, and you need to be cognizant of FFT aliasing issues.

What does he mean by it's "not calibrated"?

I was not sure either and thought the linked article might elucidate what he meant by "not calibrated".

The article points out why DSO FFTs are not always suitable as a replacement for other spectrum analysis methods including the calibration problem with the wrong units being returned.  Most people are just interested in the peaks and have no need for the units to be corrected for the actual RBW (resolution bandwidth).

[TunerSandwich]

I know the labmasters support true sample clock (ext) ref.

Indeed. If I come around I can check my 64Xi and LT264M tonight.

Update: Checked my  LT264M, and as expected even this old scope offers external sample clock input (TTL, ECL and 0V, 50ohms or 1Mohms switchable).

I just checked mine as well and found this...    I assume it's the same as your Xi?  I wish they had 75ohm and 110ohm termination as well, but no problem I can build an external amplifier or rig something up (might be easier just to get an ext clk with 50ohm out).....I wonder if I can find a place to probe that clock ref, and make sure it's not being re-sampled or skewed, inside the scope topology. 

Also I was running some advanced functions, and long time div + FFT basically locked up the UI....I can see that processor and RAM u/g is going to be necessary.

So far I am really impressed with the scopes functions and toolsets, however the update rate is abysmal.  The tool will be usable for a few dev stages, but we really need to get some more horsepower under the hood, if we are going to be sampling 5-10 second intervals, and making changes to topology in real-time. 

I'm sold though.....LeCroy scopes easily outclass Agilent, in terms of triggers and operators.  As soon as I grab an ms-500 i will check the protocol analysis and see if it's even close to Agilents solution

edit (to satisfy someone who is grumpy today) : I am quite pleased that my Waverunner 64MXi trigger and math functions, easily outclass the Agilent MSOx2k I used to have.  Especially considering the 4 year time gap in release dates, and considering the prices paid for each example. 

[XFDDesign]

I was told that the freq span in FFT mode would always effectively be equal to the bandwidth of the scope.  So in my case, the span would be 100 MHz -- not very useful if I'm looking for the harmonic content of some audio device.  Furthermore, I heard that the spectrum display is not calibrated either in freq or in amplitude.  Sounds like this may not have been completely accurate -- but close?

That would be a function of the sample rate and/or bandwidth. Let's say you were using one of those old shit TDS3000 lunchboxes. 10,000 points. You want the FFT for audio? Figure 50kHz is the max window you want for whatever reason. If the scope is fixed at 10kpts you need to oversample by 2 (nyquist), so you would set the horizontal divisions to 10,000/(2*50,000) = 10.0ms to get 100ms capture. 100ms cut into 10,000 pieces gets you 10us/sample for your 100kHz nyquist rate and 50kHz effective upper end. Your minimum resolution would be 1/0.1s or 10Hz.

It's all about knowing how to manage the FFT, but it's still an FFT which means your vertical resolution will be shite compared to a good spec an.

[coppice]

LeCroy scopes easily outclass Agilent, in terms of triggers and operators.

Statements like that are just fan boy garbage. LeCroy supply a variety of scopes sourced from different places, each with the qualities the developing company gave it. A generic statement about the qualities of LeCroy scopes is meaningless.

[TunerSandwich]

LeCroy scopes easily outclass Agilent, in terms of triggers and operators.

Statements like that are just fan boy garbage. LeCroy supply a variety of scopes sourced from different places, each with the qualities the developing company gave it. A generic statement about the qualities of LeCroy scopes is meaningless.

Interesting, because I just acquired the 64MXi, although I was never very inclined to purchase one before.  If you need further information, you can clearly see we were talking about waverunner mxi/xi scopes.  The comment was directed towards a specific person....who i have an on going dialogue with.  So he can appreciate where the statement comes from.

If you would like to be polite, and stop with your "fanboi garbage" blanket statements, maybe you could gain some insight into the specifics of our conversation.  Or you can continue to be grumpy. 

Are you looking for clarification, or just looking to try and start drama?

 Also you can clearly see that I also said the following "So far I am really impressed with the scopes functions and toolsets, however the update rate is abysmal.  The tool will be usable for a few dev stages, but we really need to get some more horsepower under the hood, if we are going to be sampling 5-10 second intervals, and making changes to topology in real-time.  "

Still seems like "fanboi garbage"?

Selective quoting, to try and bolster an opinion, is not very fair.  I did add an edit to the statement to satisfy your opinion though.  Better ? 

[Wuerstchenhund]

LeCroy scopes easily outclass Agilent, in terms of triggers and operators.

Statements like that are just fan boy garbage. LeCroy supply a variety of scopes sourced from different places, each with the qualities the developing company gave it. A generic statement about the qualities of LeCroy scopes is meaningless.

Yes and no. You're right that this isn't true for all LeCroy scopes, after all the WaveAce Series is garbage and the WaveJets, while not bad entry level scopes, are outdated and overpriced. But both Series are simply bought in from Siglent and Iwatsu, with only the label being LeCroy.

But his statement is absolutely right for LeCroy's midrange and highend Series (WaveSurfer). There's a reason why LeCroy has the reputation of being the "Mercedes amongst scopes". It has nothing to do with fanboyism. Agilent makes great scopes but even their high end can't compete with LeCroy on functionality, and Tek, well, lets better not better get there.