DSO Reliability

[J-D-H]

IMHO looking for equipment which lasts 20 years is not a good idea. Better buy a new one every 5 to 10 years so you have the latest bells & whistles.

Since I was fairly content with a Tek 465 for home hobbies (ham radio, hi-fi, general analog circuit design, etc.), I suppose I don't really need the latest features.  That said, I'd really like to get a scope with long term reliability on par with old Tektronics gear similar to my 465 (it was built in 1977 - almost 40 yrs without trouble isn't bad).  So getting back to my questions about DSOs, I can't help buy notice how similar they are (almost identical front panels).  Do you (or anyone else) know whether these things are actually the same products, just rebranded via different labels?  If that's the case then my concerns about reliability actually reduces to a general question about all of them.  To the extent that it matters, I wonder if all the brands carry similar warranties?

John

[J-D-H]

Within your budget, Rigol would be your best bet (good build quality and value for money).

In particular, the DS1054Z. Plenty of threads on it, and if you hack it, you can get 100MHz out of it as well as some other features (enable it's software options, including unlocking 24mpts of memory). Really is an amazing feature set for the money ($399 MSRP), even if you don't hack it.

And if you order from TEquipment.net, there's a code that will give you 6% off, so ~$375 (free shipping & a free gift tossed in for good measure). Can't be beaten right now for value.

PM sent.

And can 100MHz scopes be extended b to 200MHz by similar techniques?

[J-D-H]

I've said the same thing. Every year they keep adding more memory, faster sample rates and reduced prices. I'll never spend more then a grand tops on a new DSO.

Even solely from an economic standpoint, if you have to buy three or four Rigols or other cheap Chinese DSO's you are still ahead versus buying one Agilent or TEK.

That's true, but you won't get the quality, ease of use or performance that comes with genuinely professional as opposed to budget equipment.

I've spent the last week bringing up, testing and debugging a new board with the aid of my Agilent MSOX3054A. It's true that I've not used all the bandwidth - 100 MHz would have been plenty - but I have been using all four analogue channels plus many of the digital channels all together, plus serial protocol decoding, advanced trigger modes, mathematical functions and segmented memory.

The screen has got a bit cluttered at times, but throughout the process, the scope has been consistently reliable, responsive, and an absolute pleasure to use. It's never crashed, become sluggish or unresponsive, or given me an obviously incorrect measurement. I use it without thinking, and that's high praise indeed.

I can't say the same for the last Rigol scope I used, which was a DS4054. By comparison it was sluggish and, unforgivably, had bugs in it which meant the serial decoding was next to useless. Occasionally it would lock up and crash.

What's worst of all is that the Rigol wasn't badly constructed, nor were there any obvious issues in how it acquired and displayed a signal. Its hardware was fine; all its problems were in the firmware, and many of them were so painfully obvious that it's heartbreaking that they made it out of the lab in the first place.

Spec for spec, the Agilent would have been twice the price - though buying it from the 'agilent used' Ebay store negated that particular disadvantage. Unless it has some kind of ticking time bomb inside, like an irreplaceable battery slowly going flat, I can see it occupying a space on my lab bench for quite some time to come.

Hearing about the less than stellar firmware was an eye opener.  If this is typical across all brands of these low end DSOs, maybe I should look for another solution....

[G0HZU]

It may help to consider a modern chinese scope in the same way you would a modern laptop PC.

Cheap build quality and built down to a price. It's just a plastic case, a few PCBs, a display and a few connectors and a cheap PSU and a fan.

People are happy to retire/replace a laptop after just 5 years and I think the same can be said of a cheap DSO from china if it proves unreliable or can't meet the demands in 5 years' time.

You can't really compare this product strategy to your Tek 465 that was built to last many years and probably cost more to buy in the mid 1970s than a decent car.

[David Hess]

IMHO it is hard to predict what fails first. Tektronix was plagued by bad electrolytic capacitors in the late 80's and early 90's.

Was Tektronix the only one to suffer from this?  I suspect the problem had to do with the cleaning solvent used after assembly attacking the capacitor seals.

On a TFT screen the backlight is the weak point. In general weak points are components which get hot.

LED backlights may help with that if operated at low brightness.

With CRTs there is a problem when the intensity is turned off but the CRT is still operated for long periods of time which can cause cathode interference.

[J-D-H]

if we are talking hobby use...well what are you going to work with ? RF? 800MHz ARM microcontroller ? FPGA ? or small AVR at 16MHz and LF...in the last scenario a 50MHz DSO is all you need ( Rigol ) If i need spectrum analyzing / FFT i export my data to a computer and makes the calculations there so my Rigol DS1052E is all i need

My purposes are for purely hobby usage.  A BW of 200 MHz would be great (2m ham band -- 144-148 MHz), but budgetary concerns limit me to 50-100 MHz.

[J-D-H]

Interesting the OP has asked about reliability and this has barely been addressed.
As all modern scopes use at least 1 SMPS within, this is indeed a valid question.
This is generally the highest stressed part/s of any design.
As manufacturers compete on price component quality (and other features) suffers.
To have a SMPS fulltime online(powered) might be appropriate for a DSO that is in daily use but IMO the likely first point of failure over an extended period of time.
Several manufacturers have a mechanical type mains switch that removes any SMPS from fulltime mains connection, which IMO is preferable for hobbiest/intermittant use.

Mostly this type can be identified by the switch placement on top of the DSO as the force to activate the switch would displace the DSO if placed on the front panel.

Any of the recent DSO's of the more popular brands will be opening a new world for the OP with even the basic features now incorporated in DSO's.
As this is his first step into this new world my advice is to find a seller that can offer support and purchase a 100 MHz 1 Gsa/s 2 Mpts DSO.
Learn and explore the new capabilities available and get on with fixing your 465.
Depending on you future requirements, you may need little else.

Decades ago I used to rank performance and features above reliability.  Now it's the opposite -- reliability is my top concern for home EE gear.  So I wasn't happy to hear about the firmware problems already mentioned.  Maybe this means I'm looking the wrong type of scopes.  BTW, In general your whole message was very much on target.  I probably don't need all these new features, but if my 465 proves to be a beast to repair, I need something at least as capable as it was.  If I can pick up some additional features which I may find useful, that would be good too.  However if going this way gets me a buggy scope, I'd just as soon forgo that experience.

[J-D-H]

I was writing that from the point of view of a private user - someone who has to spend his own money on buying the scope and other instruments.

Well, you didn't say that your POV is limited to private users. In fact, you suggested there was no noticeable development in scopes in the last 15 years which, as I pointed out, simply isn't true.

I was merely staying on-topic: I should not have had to point this out since OP is looking for a replacement for his busted Tek 465 analog scope. Being up-to-date with the latest whizbang features is clearly nowhere near the top of OP's priority list.

Very true.

[J-D-H]

To have a SMPS fulltime online(powered) might be appropriate for a DSO that is in daily use but IMO the likely first point of failure over an extended period of time.

No doubt about the power supplies, especially their output caps, being the most common failure point in most modern devices. Then again, few devices have anywhere as many output caps per rail and per watt as the 1000Z's power supply has, and the scope only draws about 30W/ 50VA  including conversion losses so those output caps should have hardly any stress on them at all. I would be surprised if they started becoming problematic sooner than 7-10 years. On the plus side, they are relatively easy to inspect and replace if necessary; just need to remember to start checking up on them maybe once a year, just in case.

For people who really want to keep their devices around for a long time, bit-rot might become a significant concern after the 12-15 years mark.

Do any of these low end DSOs use so-called Japanese alum elec caps?  That is, the ones rated for 105 deg C, the ones which are said to last (in the PC world , in any case).

[G0HZU]

My purposes are for purely hobby usage.  A BW of 200 MHz would be great (2m ham band -- 144-148 MHz), but budgetary concerns limit me to 50-100 MHz.

A two tone test of a ham SSB transmitter is unlikely to look very good on a modern DSO compared to your 465 if you look at the envelope in the time domain. Even the big £££ Tek MSO scopes don't look as good as a decent analogue scope here because they can't match the old analogue scope in terms of intensity grading or fine detail.

However, a fairly decent DSO will offer the option of an FFT to look at two tone IMD levels in the frequency domain in the same way as a spectrum analyser (which your 465 can't do) and this is a huge bonus in favour of the DSO for SSB radio testing.

However, if you buy a cheapo DSO you may find the FFT mode to be of limited use because they often don't perform well in this mode.

I have an old Tek TDS2012 DSO here and the FFT mode is fairly reasonable and can be very useful for two tone analysis even if the overall performance of the scope is pretty lame by today's standards. I find it works well alongside my old Tek 465 for radio related stuff as long as I don't expect too much from it.

[J-D-H]

Having my Tektronics 465 fail recently was certainly depressing (great general purpose scope, IMO), but this does give me the opportunity to buy something new!  So I'm searching for a new dual trace scope with around 100 MHz BW, and settled on getting one of the ~many~ apparently Chinese made DSOs selling in the $400-450 range.

If you were happy with the 465 then why not fix it or buy another?

Then look at evaluating a new DSO in slow time. I can pretty much guarantee you will find things about a modern DSO you will not like and things you will like (in comparison to the old 465).

The best combo is to have the 465 and a DSO to get the best of both worlds. Another reason to fix the 465!

The other thing to be wary of is fan noise. Quite a few DSOs can be very noisy and this can be very distracting if you are used to working in a fairly quiet environment at home.

I'm pursuing the 465 repair, but unless I get very lucky, it looks like it may take awhile.  Depending on what I find, doing the repair my be rough.  At least it has no surface mount parts to contend with, so that's good.  However some of the circuit boards are NOT convenient to work on.  So I'm measuring my options while also troubling shooting the old scope.

What about modern analog scopes rather than these inexpensive (a relative term) DSOs?  If there are 100 MHz scopes being made with fewer "digital features", maybe I would be better off buying something like that for general home hobby projects and ham radio work?

[J-D-H]

It may help to consider a modern chinese scope in the same way you would a modern laptop PC.

Cheap build quality and built down to a price. It's just a plastic case, a few PCBs, a display and a few connectors and a cheap PSU and a fan.

People are happy to retire/replace a laptop after just 5 years and I think the same can be said of a cheap DSO from china if it proves unreliable or can't meet the demands in 5 years' time.

You can't really compare this product strategy to your Tek 465 that was built to last many years and probably cost more to buy in the mid 1970s than a decent car.

I imagine the 465 was several grand in 1977, so I agree, it's quality level was high.  I am working on it -- I hope I can repair it!  As for the laptop analogy, I have seen many of those which lasted for decades (a nearby shops sells old laptops with 486 processors -- although I can't imagine why folks buy them <g>).  So if that analogy holds, I suppose I'd be satisfied with that level of reliability.  So my main question is whether any of the modern, NON-professional scopes are know to be better in reliability than their competitors, are know to carry a better warranty, etc.  Or, are all the scopes sold at around the same price point ($350-450) similar in this regard?  Rigol has been mentioned repeatedly here, but I'm still not clear if they are head and shoulders above the others.....

[J-D-H]

My purposes are for purely hobby usage.  A BW of 200 MHz would be great (2m ham band -- 144-148 MHz), but budgetary concerns limit me to 50-100 MHz.

A two tone test of a ham SSB transmitter is unlikely to look very good on a modern DSO compared to your 465 if you look at the envelope in the time domain. Even the big £££ Tek MSO scopes don't look as good as a decent analogue scope here because they can't match the old analogue scope in terms of intensity grading or fine detail.

However, a fairly decent DSO will offer the option of an FFT to look at two tone IMD levels in the frequency domain in the same way as a spectrum analyser (which your 465 can't do) and this is a huge bonus in favour of the DSO for SSB radio testing.

However, if you buy a cheapo DSO you may find the FFT mode to be of limited use because they often don't perform well in this mode.

I have an old Tek TDS2012 DSO here and the FFT mode is fairly reasonable and can be very useful for two tone analysis even if the overall performance of the scope is pretty lame by today's standards. I find it works well alongside my old Tek 465 for radio related stuff as long as I don't expect too much from it.

Thanks for the tips.  I took the FFT option at face value, but if it isn't implemented well on these things, maybe I'll try to find another purely analog scope (that and continue to work on my 465).  All this makes me wonder whether if I drop the DSO functions, the FFT features, etc., can I buy a modern analog scope at the same price point ($350-450), but with higher quality.   Not worded well - hope that made sense....

[tautech]

Having my Tektronics 465 fail recently was certainly depressing (great general purpose scope, IMO), but this does give me the opportunity to buy something new!  So I'm searching for a new dual trace scope with around 100 MHz BW, and settled on getting one of the ~many~ apparently Chinese made DSOs selling in the $400-450 range.

If you were happy with the 465 then why not fix it or buy another?

Then look at evaluating a new DSO in slow time. I can pretty much guarantee you will find things about a modern DSO you will not like and things you will like (in comparison to the old 465).

The best combo is to have the 465 and a DSO to get the best of both worlds. Another reason to fix the 465!

The other thing to be wary of is fan noise. Quite a few DSOs can be very noisy and this can be very distracting if you are used to working in a fairly quiet environment at home.

I'm pursuing the 465 repair, but unless I get very lucky, it looks like it may take awhile.  Depending on what I find, doing the repair my be rough.  At least it has no surface mount parts to contend with, so that's good.  However some of the circuit boards are NOT convenient to work on.  So I'm measuring my options while also troubling shooting the old scope.

What about modern analog scopes rather than these inexpensive (a relative term) DSOs?  If there are 100 MHz scopes being made with fewer "digital features", maybe I would be better off buying something like that for general home hobby projects and ham radio work?

Na don't go there. 
This oportunity to get a DSO and move into a new(for you) type of test gear should not be missed.
There is so much even a entry level DSO can do that is not possible with your 465.
This you need to experience for yourself.

Grab the link from the first post in the Repair board for help with your 465 repair.

Fan noise for the Siglent SDS1000 series has never been an issue IME.

[G0HZU]

Na don't go there. 
This oportunity to get a DSO and move into a new(for you) type of test gear should not be missed.
There is so much even a entry level DSO can do that is not possible with your 465.
This you need to experience for yourself.

I certainly agree that it's not worth spending much money on an analogue scope so that rules out anything modern or expensive. A lot of hams choose to buy something like an expensive 300MHz Tek 2465 analogue scope from the 1980s but I wouldn't recommend this as an option in 2014. A repaired 465 and a reasonable (new) DSO could be had for the same money.

[David Hess]

I'm pursuing the 465 repair, but unless I get very lucky, it looks like it may take awhile.  Depending on what I find, doing the repair my be rough.  At least it has no surface mount parts to contend with, so that's good.  However some of the circuit boards are NOT convenient to work on.  So I'm measuring my options while also troubling shooting the old scope.

Most common 465 failures are repairable and in rough order of likelihood include:

• Shorted solid tantalum capacitors - the power supply is well designed so this is rarely catastrophic.
• Worn out aluminum electrolytic capacitors - The 465 has a linear power supply and this is easy enough to repair.
• Failed high voltage z-axis DC restorer - The high voltage capacitors or diodes sometimes become leaky.  If this is suspected it is usually best to just replace the parts involved.
• Failed tunnel diodes result in a loss of triggering.  Sometimes just calibration is necessary to fix this because apparently their characteristics change over time.  Replacement tunnel diodes are a problem.
• Failed high voltage multiplier - The oscilloscope will work without it but not well; usually if it fails it shorts out the high voltage supply but not catastrophically.  Replacements are often available and it is not difficult to build one.

All or most of the 465 series oscilloscopes discussed over on TekScopes@yahoogroups.com have been repairable.  Offhand I do not remember any that were not.  Some diagnostics however are best done with another working oscilloscope which can become a step down the path to collecting them.

What about modern analog scopes rather than these inexpensive (a relative term) DSOs?  If there are 100 MHz scopes being made with fewer "digital features", maybe I would be better off buying something like that for general home hobby projects and ham radio work?

I do not think a new analog oscilloscope would be any better than a cheap but new DSO.  I suspect you will get more life out of a repaired 465 than either and with care even buying one or two 465 oscilloscopes to use or as parts donors will be significantly less expensive.  I went the later route as the cheapest way to get a workable DSO and ended up with a pair of 2230s (I repaired and recalibrated both) which at this point have already outlasted some new DSOs.

[coppice]

I imagine the 465 was several grand in 1977, so I agree, it's quality level was high.

In 1977 a 465 was about a years salary for a fresh graduate engineer (at least in the UK, where I come from).

[PaulAm]

At the risk of getting off topic, what's wrong with the 465?  They're pretty easy to repair for the most part.

[nanofrog]

At the risk of getting off topic, what's wrong with the 465?  They're pretty easy to repair for the most part.

In general, I'd be concerned with weak CRT's given their age (thinking in terms of buying off eBay).

[Wuerstchenhund]

Hearing about the less than stellar firmware was an eye opener.  If this is typical across all brands of these low end DSOs, maybe I should look for another solution....

How about a somewhat newer second hand scope? There's plenty of stuff available which for most part is pretty reliable.

And buying used means you can get more/better features (i.e. proper FFT) than on new entry-level scopes.

What about modern analog scopes rather than these inexpensive (a relative term) DSOs?  If there are 100 MHz scopes being made with fewer "digital features", maybe I would be better off buying something like that for general home hobby projects and ham radio work?

"analog scope" and "modern" is an oxzmoron, considering that the big brands have stopped making them many years ago, as has CRT production in general.

[DanielS]

Do any of these low end DSOs use so-called Japanese alum elec caps?  That is, the ones rated for 105 deg C, the ones which are said to last (in the PC world , in any case).

While Japanese caps are of generally higher quality than Chinese ones, what usually kills caps in short order in poorly designed power supplies is under-specified ripple current and high temperature. If you pop the lid off cheap Chinese PC power supply, you will often find caps rated for only 1A_RMS ripple on supply rails that should have enough caps to handle at least 4A_RMS and heatsinks that may exceed 80C.

Considering how little power the DS1000Z uses and the ridiculous number of Samxon caps in its PSU, I doubt either issue will be a problem for the first several years as long as the fan works and vents do not get clogged.

People who have jitters about the caps can always re-cap the power supply in 3-5 years with whatever their favorite brand is. If you buy electrolytics in bags or strips of 100, the preventive replacement should cost less than $15 in parts, even less if you only replace one or two caps per rail because your single cap already has better specs than all 3-4 OEM ones combined.

[David Hess]

While Japanese caps are of generally higher quality than Chinese ones, what usually kills caps in short order in poorly designed power supplies is under-specified ripple current and high temperature. If you pop the lid off cheap Chinese PC power supply, you will often find caps rated for only 1A_RMS ripple on supply rails that should have enough caps to handle at least 4A_RMS and heatsinks that may exceed 80C.

I think there is something else going on with capacitor reliability as well.

In the past, ripple current limitations were poorly understood so good designs compensated by derating the capacitors significantly more than neccessary.  As time progressed, ripple current became more important and capacitors specifications became more detailed and accurate so now capacitor lifetime based on ripple current specifications may be finely tuned but the result of this is that properly designed equipment fails just past the warranty or expected operating lifetime do to capacitor failure instead of other reasons.

I have mostly noticed this as a general trend in personal computer power supplies but it seems to apply to consumer electronics as well.  Cheap devices have short warranties and the expensive devices may have long warranties but both tend to fail just out of warranty do to the capacitors wearing out.

If Rigol designed their power supplies "properly", then I would expect the same thing.

[TunerSandwich]

with modern designs moving more and more towards very advanced SMPS, and ditching the traditional LDO and linear regulators, it's very hard to gain insight from an analog scope these days.  Scopes have sort of transcended their traditional uses and limitations. 

in terms of reliability, modern SMPS and POL systems have become reliable, to the point of not really having to question them.  however these systems require more and more bulk caps, and if the caps used are dodgy, that is a potentially HUGE problem.

I don't think there is any real compromise in quality in Rigol PSU's.  They are as good as anything out there. 

On the front of reliability, an older scope is going to be impossible to repair (in some situations).  The only reason I can see for using anything (other than a good modern DSO/MSO) is for characterizing noise in highly critical power supplies. 

If the work you do doesn't require such tools, I am sure it could benefit from some other modern equivalents.  For example.....audio gear.  Could you imagine going back to using older THD and RTA?  With modern spectral analysis and harmonic analysis tools, it's hardly possible to imagine going back to less parametric analysis. 

It's nice to have older gear for very simple and specific things, but the pace of modern consumer technology just doesn't allow for the "traditional" toolset.  Believe me I don't think that is necessarily a good thing, but it is reality. 

In a production environment, I just don't see how it's possible to spend the time to maintain old dinosaurs.  Example....i owned a recording studio for many years....and people used to bring in all kinds of whacky "vintage" gear.  Old altec compressors etc.....they had the illusion that they were somehow "better".  That concept quickly changed when they spent all of their session time tracking down the radio signal making it's way through the piss poor designs of the older gear. 

Example, i have a nice "mint" Pultec EQP1A (uber lusty gear-slut vintage EQ).....although it's fully rehabbed and meets spec....my modern clone (EAR822) simply decimates it, in terms of performance and noise floor.  Not to mention I can actually source the parts to fix it.  People get caught up in ridiculous notions that something from an era gone by is somehow "better". 

Don't mean to take it off topic, but I think these are valid observations, that can easily be applied to any piece of "gear".  There are most certainly reliable high performance tools being sold as new...

[DanielS]

I think there is something else going on with capacitor reliability as well.

I have mostly noticed this as a general trend in personal computer power supplies but it seems to apply to consumer electronics as well.  Cheap devices have short warranties and the expensive devices may have long warranties but both tend to fail just out of warranty do to the capacitors wearing out.

If Rigol designed their power supplies "properly", then I would expect the same thing.

The way capacitor failure is generally quite predictable is really a plague in consumer devices; I have lost count of how many devices with under-rated Fuhjyuu caps I have repaired and that includes many of my own including both of the LG LCDs I am using on my PC: the original caps, all Fuhjyuu, failed after about three years, I have replaced them with Panasonic FM-series caps and they are still working today, 5-7 years after the repairs. The oldest of the two is 10 years old now and its backlight started having trouble warming up three years ago; still works fine after a five minutes warm-up.

Another way to think about it: can Rigol really afford to under-engineer the power supply in that thing? Any electrical noise that gets out of the PSU is more electrical noise the system-wide design needs to deal with and be over-engineered for, so it should be much cheaper and simpler to over-engineer the PSU to eliminate as much switching noise as practically possible at the source.

In typical consumer electronics scenarios, the end-user also lacks the tools and knowledge to call BS if the manufacturer claims their device is working normally to weasel their way out of a warranty claim. With an oscilloscope, the user obviously has the equipment and likely the knowledge (or access to it) to call BS if the manufacturer tried to deny an issue existed so there is nowhere near as much room to cut corners without a high probability of getting called in on it.

Selling measurement instruments is a lot like selling guns and ammunition to burglars or making unpopular policy changes in social media networks: tables can turn on you at the drop of a hat so you had better think twice before backstabbing anyone. Rigol wants to gain more mindshare around the world and I doubt they would want to compromise that by producing instruments with significantly sub-par reliability even at the low-end - at least I would not be willing to take that chance.

[TunerSandwich]

I think there is something else going on with capacitor reliability as well.

I have mostly noticed this as a general trend in personal computer power supplies but it seems to apply to consumer electronics as well.  Cheap devices have short warranties and the expensive devices may have long warranties but both tend to fail just out of warranty do to the capacitors wearing out.

If Rigol designed their power supplies "properly", then I would expect the same thing.

Another way to think about it: can Rigol really afford to under-engineer the power supply in that thing? Any electrical noise that gets out of the PSU is more electrical noise the system-wide design needs to deal with and be over-engineered for, so it should be much cheaper and simpler to over-engineer the PSU to eliminate as much switching noise as practically possible at the source.

The PSU design, and component selection....as well as the internal shielding in my DSO2000A-s is some of the best I have seen.  It's not "over-engineered", in the sense that a bridge could never be over-engineered.  It's just more than is necessary to meet the bare minimum specs, to actually make the scope work.  I applaud the quality or Rigol engineering and implementation.

I would put much more faith in a Rigol or other modern "quality" scope, than a 20+ year old dinosaur.  Especially something with a CRT or improperly characterized caps....