Products > Test Equipment
Test Equipment Anonymous (TEA) group therapy thread
mnementh:
--- Quote from: tautech on May 20, 2018, 12:07:06 am ---
--- Quote from: mnementh on May 19, 2018, 11:13:13 pm ---I did that same job on my Tek 2230 a decade ago; then replaced the HV multiplier flyback again this last time I worked on it. Altogether a right crunky affair; I get that the whole mess allowed them to run the beam at lower current, therefore better response and sharper focus at higher frequency... but damn. It's one of those designs that just seems to taunt Murphy.
And worse yet, they "inspired" the designers of your scope to follow in the same ill-advised foosteps...
mnem
Not a fan. Not a grommet, either.
--- End quote ---
It's a pretty standard CRT design and mostly reliable with modern components but the EHT and PDA is still often a primary failure point in CRO's, such are the stresses the components are under.
It's little wonder these days scope displays are nearly exclusively LCD.
--- End quote ---
If by "Mostly reliable" you mean "most of the reliability issues are within these components on models that use this design" then I'll agree with you. :-DD It seems to be the leading cause of death in the 22xx family by an order of magnitude for sure; their rate of extinction is directly proportional to the number of donor units left to scavenge HV multipliers from.
And before you say it doesn't, YES, it does have EVERYTHING to do with the design. Higher voltage in the primary means higher stress in everything in the HV transformer, and any distortion at those voltages becomes some pretty nasty reverse EMF.
IMO, the reason 'scopes today are nearly exclusively LCD is because we only have a relative handful of engineers who know more actual electronics theory than what they absolutely need to interface with a processor. It has nothing to do with what is a better technology; when it comes to troubleshooting noise issues I still look to my CROs first.
mnem
That's muh story and ah'm stickin' teww itt.
Cerebus:
--- Quote from: bd139 on May 19, 2018, 11:16:53 pm ---To quote a friend of mine who was dating a girl in Billericay; "Essex made me itchy". All is not forgiven yet :-DD
--- End quote ---
"I come from Essex,
In case you couldn't tell.
My given name is Richard,
And I'm doing ... very well."
tautech:
--- Quote from: mnementh on May 20, 2018, 12:31:44 am ---
--- Quote from: tautech on May 20, 2018, 12:07:06 am ---
--- Quote from: mnementh on May 19, 2018, 11:13:13 pm ---I did that same job on my Tek 2230 a decade ago; then replaced the HV multiplier flyback again this last time I worked on it. Altogether a right crunky affair; I get that the whole mess allowed them to run the beam at lower current, therefore better response and sharper focus at higher frequency... but damn. It's one of those designs that just seems to taunt Murphy.
And worse yet, they "inspired" the designers of your scope to follow in the same ill-advised foosteps...
mnem
Not a fan. Not a grommet, either.
--- End quote ---
It's a pretty standard CRT design and mostly reliable with modern components but the EHT and PDA is still often a primary failure point in CRO's, such are the stresses the components are under.
It's little wonder these days scope displays are nearly exclusively LCD.
--- End quote ---
If by "Mostly reliable" you mean "most of the reliability issues are within these components on models that use this design" then I'll agree with you. :-DD It seems to be the leading cause of death in the 22xx family by an order of magnitude for sure; their rate of extinction is directly proportional to the number of donor units left to scavenge HV multipliers from.
And before you say it doesn't, YES, it does have EVERYTHING to do with the design. Higher voltage in the primary means higher stress in everything in the HV transformer, and any distortion at those voltages becomes some pretty nasty reverse EMF.
mnem
That's muh story and ah'm stickin' teww itt.
--- End quote ---
And fair enough too. :)
But let's look a little harder at this common and historical design, it requires quality and well spec'ed componentry, something the bean counters for decades have strived to reduce BOM cost on. PSU's, caps, in fact most component ratings are pushed to high % limits these days and maybe using modern components they'd be more reliable but it doesn't negate the fact LCD displays are now much cheaper to make than a CRT.
Watch this and tell me that isn't so :P
--- Quote ---IMO, the reason 'scopes today are nearly exclusively LCD is because we only have a relative handful of engineers who know more actual electronics theory than what they absolutely need to interface with a processor. It has nothing to do with what is a better technology; when it comes to troubleshooting noise issues I still look to my CROs first.
--- End quote ---
The world is a changing m'boy. :box:
Good DSO's and knowing how to use one and you won't miss much.
mnementh:
Of course it's cheaper... but that doesn't necessarily mean BETTER. In fact, it USUALLY means one or more compromises. ::)
And the fact you have to qualify that statement is the crux of the issue. You won't miss much. That says it all.
How many times have you heard someone tell a story of some inaccuracy in a modern DSO that was made glaringly obvious once the user switched to an even moderately well-specced analog 'scope? Sure, it's not MOST of the time. But sooner or later, you'll miss something.
My daily driver DS1054Z is a perfect example; it is a serviceable, well-rounded DSO that has amazing functionality at an amazing price point. For MOST of what I need a 'scope to do, it is all I need and more. This is a SUBJECTIVE evaluation, however, and purely based upon my needs at this moment.
The fact remains, as anyone who's used a vintage Tek in its prime will know, that it is OBJECTIVELY a crappy 'scope with poor definition and a number of QC issues and outright design flaws that introduce noise and make it actually distort the waveform horribly if pushed anywhere near its limits. This is in stark contrast to what we've come to expect from properly designed analog 'scopes, which will typically perform up to their rated frequency and well beyond, like bd139's latest acquisition, a 30-year-old 50MHz 'scope that isn't even fundamentally healthy, yet still performs at 125% of rated spec, and is capable of producing usable results at nearly twice rated spec.
The bottom line is... we STILL don't KNOW that what even a GOOD DSO shows us is right; we just trust that it is PROBABLY showing us a mostly accurate chart that mostly represents the waveform. Plenty of times we have to outwit the damned things to make sure what we're seeing (or worse yet, what we're NOT seeing) isn't just some damned artifact of the acquisition process.
And when we question what our DSO is showing us, what tool do we always reach for as a yardstick, just to be sure? Not usually another DSO... but rather the best analog 'scope we have handy set so we can "see with our own eyes" what we're not sure about... even if we know we'll only see a shadow or a momentary glimpse of what we're looking for to corroborate what we see on our DSO.
Yes, I know we live in an age where complex non-repetitive waveforms are the norm, and you MUST have a DSO (and usually a protocol analyzer as well) to be able to troubleshoot even the most basic devices anymore. But that does NOT in any way diminish the value of a quality analog 'scope. It only rightfully justifies their place on anybody's workbench.
The proof of this is that pretty much since their inception, whenever a manufacturer needed to "demonstrate" that their DSO is reproducing a waveform accurately, they held it up against a 24xx or a 7xxx series Tek 'scope (or similar, though what is "similar" is certainly a matter of argument) in prime condition.
Yeah, yeah... I know... not any more. There are a lot of newer 'scopes they use now as the "benchmark". But all of them ultimately were compared directly or indirectly against one of these benchmark 'scopes at some point in their history.
Just because we live in the digital age doesn't mean that analog is a thing of the past. Every digital signal must exist in the analog domain. This means a well-balanced understanding of analog circuitry and what does and does not work is still critical.
That, to me, is the most telling argument in favor of keeping CROs (especially these benchmark models) alive for at least a few more generations. If all they do is teach the next generation, by dint of having to learn how to service them and keep them alive, how a properly designed analog circuit works... they're still an invaluable tool.
mnem
*Toddles off to ded*
Brumby:
My 15MHz Hitachi CRO was able to show me a 27MHz RF transmission with enough amplitude for me to see the transmitter working as expected. Would a similar bandwidth DSO?
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