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Test Equipment Anonymous (TEA) group therapy thread

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Specmaster:

--- Quote from: Brumby on May 20, 2018, 06:02:43 am ---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?

--- End quote ---
I would expect not, you are asking it to be able to perform at almost twice its design criteria. [emoji44]

From mobile device so predictive text might have struck again [emoji83]

Specmaster:

--- Quote from: mnementh on May 20, 2018, 04:55:10 am ---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*

--- End quote ---
Check through Daves video's and I think you will find many references to the fact CROs are better performers in lots if ways and noise is just one them. In fact he advocates that every lab should have at least one CRO on its bench. Me, I'd love to be able to afford both but sadly DSOs are still out of my reach so I'll carry on with my 4 CROs for a while yet.

From mobile device so predictive text might have struck again [emoji83]

Specmaster:

--- Quote from: Cerebus on May 20, 2018, 12:43:40 am ---
--- 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."

--- End quote ---
Couldn't agree more, I feel much safer in Essex then I would / do in London area for instance. I have worked all over the London area for the last 35 plus years and never once felt at risk, however that is not the case these days for a whole host of reasons.

I'm afraid it's the same situation though, it's the minority who spoil it for the majority. Because of the authorities inability to deal with those people effectively, I don't see things getting better anytime soon. [emoji850]

From mobile device so predictive text might have struck again [emoji83]

Specmaster:

--- Quote from: bd139 on May 19, 2018, 11:12:17 pm ---Yes this has the original caps in it. They are rotten old bits of crap. Flat ceramics, speckled and cracked and film ones which look cracked too. Will be replaced. I've priced a few up and they're not that expensive fortunately. Will order next week once I've checked it over properly. You can apparently get a suitable equivalent multiplier from a company called High Voltage Modules in Braintree here in the UK. I'll give them a call.

Thanks for the link. I've got a spare HT transformer now in the other scope so I might unwind and count it out.

Have just ordered power supply caps. Cost a whopping £5 from RS so far. Embarrassingly small compared to the originals!

--- End quote ---
Yep, find that happens a lot these days as they get better quality, kind of begs the question though that if they make them to the original size, wouldn't they also last a lot longer?

From mobile device so predictive text might have struck again [emoji83]

med6753:
Well I found out what's wrong with Channel 2 on the Tek 465 and it's not pretty. The X100 attenuator comprising of C60 and C61 has cold solder joints. I was able to pull the assembly off the board with little effort. Now normally this wouldn't be a big deal. Put it back on and re-solder. But not this board. You can't get to the backside of the vertical board unless you pull it. And it's going to be a nightmare to pull. I'm thinking of cutting my losses and just using it as a single trace scope.

Bd139, what do you think? You have a lot of experience with 465's. Pull it or leave it? Right now I'm going to get some sleep. Had to work some overtime tonight and then come home and discover this shitty issue.    :rant: :wtf:

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