Tektronix 455 VS HumgChang 5502 - Page 1
Forum section: electronics / testgear

author: amemic
author_rank: Contributor
timestamp: August 18, 2015, 01:33:55 pm
content: Hello!I am finally saving some money to get a scope, even though I am in the electronich since I was 10, I never got around of getting a scope, you just can't do much test and diagnostics without it...So in my available price range, I can get these as used:-$88 Tektronix 455 (in the ad it looks that the case is cracked, glued and taped, but the scope seems to work)- $50 HungChang 5502 (had this same one in the high school lab, seems to work allright)And this thing, which seems to be some kind of kit, is that any good? It's about $38http://www.njuskalo.hr/elektronski-uredaji/osciloskop-200-mhz-oglas-16078505And also I have option to get myself an UNI-T UT81B handheld thingy as a brand spanking new in the store for $280I know that brand spanking new is always better, but still, that thing has it's limitations...

author: Muxr
author_rank: Super Contributor
timestamp: August 18, 2015, 01:55:15 pm
content: The best deal in scopes is the Rigol 1054z. For the price, you get everything and then some. Anything cheaper is usually not a good bargain. Especially if you also have to spend time fixing and repairing old scopes.Analog scopes are alright if you have one laying around, but I wouldn't buy one personally as my first scope. If you can, really save up and buy a proper DSO like the Rigol I mentioned, it is so worth it.

author: rvalente
author_rank: Frequent Contributor
timestamp: August 18, 2015, 05:28:09 pm
content: Well, we got one 455 here in the shop, which no one uses, she came for free, in some bargain my dad did in the past.Sincerely? Its just an analog scope which looks way much better than it really is, few resources, just like any analog scope but he is full of custom parts, very little repairable.I the world of analog scopes, I prefer the Tek 22 series, we own the 2215 and 2235, very simple made and rugged.If you can get your hands on the 2220 or 2221, they have digital storage, which is nice!But as anyone would say, this units nowadays worth only $150 or less.$300+ you buy a modern Rigol or low cost used (sometimes new) Teks or Agilents/Keysights$300 mays look a lot, and it is, but T&M equipment often last forever when taken good care, we've got HPs made back in the 60s

author: amemic
author_rank: Contributor
timestamp: August 18, 2015, 06:29:24 pm
content: Well, rigol does sound nice, and I know that sooner or later I will need 4 channels, but at the moment I have no scope, and quite a tight budget, in cash from th used ones I can get ones that are up to $100, and here in my country you can't get much for that I narrowed down to those few that aren't vacuum tube types like this one:http://www.njuskalo.hr/stare-stvari/osciloskop-grundig-oglas-14702039And the budget for the new ones is limited to $300 by my credit card (i already got myself some treats so this is left until i pay off others). But the thing is for $300 I can't quite get the new Rigol or, god forbid, agilent, because you'll get ripped off just like that, I've found Siglent SDS 1052DL for little over $350 but as I said it's over budget, not much but it is :-)The closest to the budget limit is UTD-2025C but I'll have to wait a few months so my limit raises enough so I can buy the thing :-)So, what I need is opinion between those available, their repairability, quality, and if someone has been using those, some experienced advice :-)I know these are the days of DSO, but at the moment I can afford myself only analog thing, which I presume will be enough for now...

author: oldway
author_rank: Super Contributor
timestamp: August 18, 2015, 07:38:02 pm
content: Tektronix 455 is a very old model, the Hung Chang is a low end chinese brand.As you already know the hung Tchang 5502 and that it is in good working condition, I would buy this one.I would prefer an HM605 Hameg if possible...but it is probably more expensive.

author: PaulAm
author_rank: Frequent Contributor
timestamp: August 18, 2015, 08:02:01 pm
content: The 455 is a fairly old scope, but it does use ICs and its 50 MHz. It was built from 1975 to 1980. Here's a link to the tekwiki page:http://w140.com/tekwiki/wiki/455There are links on the side to schematics and a service manual.Pros: it's a Tektronix, there are service manuals available and those old scopes hold up amazingly well.Cons: It's at least 35 years old. But's it a Tektronix. I have a 50+ year old 454 sitting on my desk I use all of the time when I need a quick look at something.If it breaks, unless it's a power supply problem, you'll likely need another scope to fix it. There's a nonzero chance of that happening, but if it's working now it will probably continue to work. Sometimes you can even use a scope to probe itself.If you can check it out, read the manual and test it out. You can use the built in calibrator to exercise most functions.Yes DSOs are the standard now because that's the way scopes are built. They have many significant advantages over an analog scope, but that doesn't mean analog scopes are useless. Hands down, it's waaay better than no scope.

author: amemic
author_rank: Contributor
timestamp: August 18, 2015, 08:18:32 pm
content: Yeah, I was leaning toward the HungChang, simply because I was already working with these...but the main issue is getting proper documentation when it goes bonkers and I have to fix the thing...I gotta say that 455 has nice collection of manuals on that site, and what is also a nice touch it is afterall a 50MHz in comparison to 20MHz on a HungChang...@oldway: We had a few of those hamegs in hig school in the other lab...that thing was awesome, but those thins here are over $250...Example, this 20MHz HM203 is $400:http://www.njuskalo.hr/mjerni-instrumenti/hameg-hm8018-lrc-metar-modul-oglas-15178159The scope is pretty great, we had some good fun with that in the lab, but for my private lab fairly ovver the budget

author: rvalente
author_rank: Frequent Contributor
timestamp: August 18, 2015, 09:30:13 pm
content: Let me make a correction, the one we own and I have confused is the TAS455.For this old 45x, 46x and 47x they are very robust, the one know issue is the HV triplicator, which we once solved with a CRT monitor one.I personally think they're vintage gorgeus!

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 19, 2015, 05:14:40 am
content: Quote from: amemic on August 18, 2015, 06:29:24 pmIf you can stretch to $329 you can get a Siglent SDS1102CML which is quite a decent entry level scope:http://www.ebay.com/itm/Siglent-SDS1072CML-Digital-Oscilloscope-70MHz-1GSa-s-Real-Time-Sample-Rate-2Mpts-/300915764006?hash=item460ffa2b26I'd rather save for the remaining $29 than to invest $100 in a 20+ year old analog clunker which is very likely well past most of it's useful life, and these days has very limited use anyways. As Muxr says if you happen to have one laying around or get one for free (or a few bucks) then yes, go for it, but investing $100 in an analog scope these days doesn't make much sense in my opinion. IThere's a good chance that after spending $100 on an analog scope you'll quickly find yourself missing things that even the most basic DSOs can do (i.e. waveform storage) and you'll end up in a similar situation as you're in now - just with $100 less.

author: amemic
author_rank: Contributor
timestamp: August 19, 2015, 09:50:41 am
content: Well, I don't think that the credit card company will allow me to buy $300 device in installments on ebay...that's why I'm pretty much limited to my country's storesI wish that tere is someone in my country that gives away scopes just like that, or sells them for a few bucks...But the thing is, people here tend to use things until they are completely useless or sell them while it works fairly well, but for a fairly high price because they are in need for the money...I was checking out prices few years ago and they were pretty much the same from $200+...that's why I narrowed down to those two in an acceptable price range that pop out from time to time at these prices...

author: oldway
author_rank: Super Contributor
timestamp: August 19, 2015, 12:59:37 pm
content: QuoteI don't think that's such a great problem.These Hung tchang are rebadged under different brands.For example, I found the schematics and service manual of Hung Tchang 6502 as Protek 6502.For sure, it is certainly no very far from 5502 and could help if needed.NB: analog oscilloscopes are still usefull for all what does not need storage feature.For example, analog circuits, power electronics, repair, ...DSO is a must for digital electronics and development of new products.

author: amemic
author_rank: Contributor
timestamp: August 19, 2015, 03:04:35 pm
content: Quote from: oldway on August 19, 2015, 12:59:37 pmWell i did found out that protek is a rebadged HC, but I found 3502 manual and as you said 6502...but only a small part of the schematics for 5502..Quote from: oldway on August 19, 2015, 12:59:37 pmThe thing is, I pretty much need the scope for repair and some testing...tek would be a nicer touch because of the 50MHz but I'll see will it be worth since the thing is in the other city... :-)

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 19, 2015, 06:41:30 pm
content: Quote from: oldway on August 19, 2015, 12:59:37 pmA DSO is not just for digital stuff because it's a digital scope, that's nonsense. Analog scopes, and even more so the low end scopes that were mentioned here, are mostly useless for modern power electronics, and even most of today's analog circuits.Of course, this doesn't help if the OP can't stretch to a DSO or for some reason doesn't want to buy abroad. Beggars can't be choosers.

author: amemic
author_rank: Contributor
timestamp: August 19, 2015, 07:41:25 pm
content: Quote from: Wuerstchenhund on August 19, 2015, 06:41:30 pmIn what way would they be useless?Quote from: Wuerstchenhund on August 19, 2015, 06:41:30 pmI am limited to buying here, mostly due to high shipping costs and import charges in my country, when they see a scope, even a low end one, their level of knowledge about electronics guides them into thinking that I bought a part of a space shuttle and then they charge the fee they like...usually the higher one...The only option to get something from abroad is to get in my car and drive out the country and buy somethinig used from the ads in the EU...which in total would probably cost me like a brand spanking new DSO in the store here...so...I don't have a wide choice...just needed some help to choose between those I narrowed down to... :-)

author: oldway
author_rank: Super Contributor
timestamp: August 19, 2015, 08:11:38 pm
content: Do not worry, do not pay attention to some participants of the forum who think that sophisticated measuring devices can compensate for their lack of knowledge and experience.For over 50 years we only used analog oscilloscopes, we even went to the moon with electronics developped, produced and tested with analog oscilloscopes, and suddenly they have become useless ...You are kidding ?Everyone can not buy measuring instruments of several hundred or even several thousand bucks.We also have to respect those who have a small budget.

author: amemic
author_rank: Contributor
timestamp: August 19, 2015, 11:11:33 pm
content: That's why I asked Wuerstchenhund in what way would it be useless...I was using analog scopes in high school labs, they were a treat to work with, they also taught me quite a lot about inner workings of an analog scope, we even had an entire class about measuring instruments, and the analog scope was explained in fair detail....it is an awesome thing, and now everyone says DSO this DSO that forget analog...DSO is nice, of course it is nice to have a latest technology, but still, they show the same thing on the screen if you connect them on the same test point...and they are out of budget to a lot of hobbyists...I mean really, if you work with electronics every weekend, do you really need $500 scope? Or will the good old timey analog do the job? That thing about doing digital stuff on a DSO is just rubbish, I was scoping digital signals on a Hameg 9 years ago...and it worked a treat...In the end my choice is still between tek and that hung chang...I really like that 50MHz range on Tek, but We'll see is it worth just paying shipping or driving 90km to test it out personally...or just go with the hungChang

author: vk6zgo
author_rank: Super Contributor
timestamp: August 20, 2015, 04:14:25 am
content: It may well be that in the work Wuerstchenhund is doing,an analog Oscilloscopeis"useless".In other fields,it is every bit as usable as a DSO.He is prone to hyperbole,but then,that is common among people of strong opinions.Wuerstchenhund says that for another $29 on top of your budget,you can get a Siglent on eBay.He hasn't included postage,which,by itself would elevate the price of the instrument to around four times that of the Tektronix 455.Add the import charges you referred to,& it becomes a very costly exercise,for the added benefits of a DSO.If you had a large budget,I would say "Buy a Rigol DS1054z"as they do seem to offer "the best of both worlds",but as it is,I would recommend The Tek over the Hung Chang,for the following reasons:Tektronix qualityAvailability of Technical information,&,last,but by no means least-------The 455 has a delayed timebase,which adds significantly to the capabilities of the instrument.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 20, 2015, 05:38:16 am
content: Quote from: amemic on August 19, 2015, 07:41:25 pmFor example, try to do a B-H analysis on an analog scope, or line harmonics (which you can't do, because an analog scope can't do FFT), which are all pretty common tasks for power electronics. Plus an analog scope will often "hide" common mode noise because it disappears on the screen due to not causing sufficient luminance of the phosphor (I think Dave even did a video showing this a while ago), which means your signal might look nice and clean on an analog scope while in reality it's very noisy.Quote from: vk6zgo on August 20, 2015, 04:14:25 amWell, that's your opinion, but the fact is that even Dave doesn't recommend an analog scope for beginners any more. $100 doesn't look like much but it's a lot of money for an antique which is statistically close to the end of its service life, in case of the Tektronix full of unobtainium, and doesn't offer the most basic capabilities like storage and FFT which, despite the common mis-belief of some oldtimers that digital scopes are for digital circuits only, are even more useful for analog work. There's *a lot* you don't get with an analog scope than even a bottom-of-the-barrel DSO gives you.QuoteWell, the seller had included postage (" FREE Expedited Int'l Shipping" for those that speak English), which you would know if you had at least looked at the link (let's talk about hyperbole again, shall we?)But as I already said, in the situation the OP describes, beggars can't be choosers, so I guess he's stuck with these two scopes. But there is a good chance that if the OP's interest for EE is serious that, after spending $100 on one of these old analog scopes, he'll quickly run into its limitations and will have to spend the $300+ for a DSO anyways.

author: oldway
author_rank: Super Contributor
timestamp: August 20, 2015, 06:28:39 am
content: You are frankly bad faith.You cite a single example to say that in general an analog oscilloscope is useless .... there are hundreds of applications where the analog scope is helpful.As for noise, the analog scope mainly cover the noise of his own amplifier and that is an advantage because this noise does not exist in the signal to be analyzed.Digital scope is unable to show a correct pattern of this kind of noise.QuoteI have 30 years experience in power electronics (SMPS, No break's, Battery charger's, DC drives, Inverters, ...) and NEVER needed to do this !Dave said that,.... Dave's opinion, ...Dave is not God...Dave is not God...

author: vk6zgo
author_rank: Super Contributor
timestamp: August 20, 2015, 06:36:15 am
content: It's only free postage for buyers in the UK,USA,Germany,& Japan,as far as I can see----I haven't checkedallof the countries on the list.Certainly,for both Australia & Croatia,the postage is US$39.99.As any 'scope is,in normal use, a single ended device,it is not going to see "common mode noise" correctly,in any case.The number of times when an FFT would have been useful to me are vanishingly small,but in fairness,many times I had access to real spectrum analysers.As I commented,your work may well need a DSO,but that doesn't mean everybody does.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 20, 2015, 08:59:03 am
content: Ponder for a moment why Jim William continued to use a 50 Mhz Tekronix 547 at Linear Technology and 50 Mhz Tektronix 556 at his home lab for the entire duration of his technical work. Jim had easy access to the most state of the art instrumentation yet he continued to favor the Tektronix 547-556-7904A-7104.Jim is not the only one who continues to hold this belief and choice of instrumentation.Do not be fooled into believing more scope bandwidth is always better, this is a measurement specific requirement.Bell & Whistle technoid features do not always aid in measurement ability or accuracy or allow the user to see-understand what is actually happening in a circuit. This ability and knowledge originates from the user far more than the item of instrumentation involved.Econo brand made in China is more often than not of very questionable quality, durability, repairability and trustworthiness. This is generally NOT true for instruments made by Tektronix and they are of known quality, serviceability, accuracy and trustworthiness.What appears to be a low cost value can turn out to be a very expensive mistake in the long run. An awful lot of time, resources and much more can be wasted due to poor instrumentation and implementation of instrumentation and instrument technique... which applies regardless when using an analog scope, DSO or any other measurement instrument.What is becoming quite apparent, DSO users tend to rely on the data box rather than fully understanding what is on the waveform display. This is likely due to the acquired skills needed to fully understand and interpret what one is looking at. This is specially true for all that analog stuff.Bernice

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 20, 2015, 09:09:01 am
content: God...Always question monotheism, authority and "GOD". Do not simply accept pontification or kernels of knowledge from those who claim to know it all."Humans have a great talent for self-deception."BerniceQuote from: oldway on August 20, 2015, 06:28:39 am

author: alsetalokin4017
author_rank: Super Contributor
timestamp: August 20, 2015, 10:05:05 am
content: Well... I am one of those people who believe that any scope (almost) is better than no scope at all, and if you are just starting out and have only a couple hundred dollars to spend on a scope, you will be better off with a good used Tek analog scope, right now, and if you stay in the hobby and can save up 400 dollars then you can get a Rigol or Atten or similar bottom-end DSO later, once you know how to use the analog scope. The money you spent on the Analog scope can be counted as "tuition" since you will actually learn something about scoposcopy in order to use the Analog scope meaningfully, and this learning will make your DSO experience all that more fruitful.I'll bet there are beginners here on this forum who own DSOs who cannot compute the frequency of a sine wave using the trace itself, screen graticule and timebase settings alone, or use the graticule to determine the RMS value of a sinusoidal signal. So what, you might say, these are obsolete skills. Well, so is knot-tying, but it's good to know anyhow and someday may make a big difference in your life.

author: amemic
author_rank: Contributor
timestamp: August 20, 2015, 10:18:40 am
content: Guys, I just wanted to pick and choose between available scopes,I didn't think that it will turn into Analog vs digital discussionI am personally old-school guy, and I do like the old timey analogy stuff, but I do also realize goodness and advantage of the new digital technology, but it doesn't mean that either is a must have...truth to be told it would be best if you had both..Although what I've noticed with all new technology, just like with phones and calculators, it spoils us, very few people today knows someones phone number, it's all in the phone, no one does the math without calculator, you can see where I'm going with this...we're putting less and less effort in things we do...many would say that's progress...is it really?In the end, I will try to get my hands on the Tek, and only in case I'm not able to get it in any way, I'll go for the HungChang...darn it...in the end, if I finalyy get a raise this mont maybe I get both@alsetalokin: Well, I do know how to work with a analog one, even so, as I said in earlier post, I had an entire class devoted to measurment instruments, including the scope...but I guess I am a bit rusty... :-)Now just to get Freq Gen and play with Lissajous curves a bitP.S.Sorry if there are mistypes or dropped letters, this keyboard is horrible, I'm lazy to get the batteries for the logitech one i usually use so I'm typing with some cheapass laptop style key keyboard...it has low profile keys, but you really have to press the key down...not quite good for fast typing...

author: alsetalokin4017
author_rank: Super Contributor
timestamp: August 20, 2015, 10:29:04 am
content: @amemic: Yes, get the Tek. I don't know about the HungChang, but there is a _lot_ of help and information on the web about the old Tek scopes, and should it need repair you will get a lot of help both in manuals and parts, and also advice from experienced users and fixers. You've got a delayed timebase feature on the Tek, I believe, and this increases its usefulness immensely over scopes that don't have this capability.If you are interested in Lissajous figures then the Analog scope is going to be superior to almost any DSO you'll be able to afford. In the winter, I fire up my old Tek RM503 and four oscillators (two inputs for X and two for Y, inverting and noninverting, on that scope!) and have it working as a room heater and "mad scientist" display simultaneously. My Rigol 1054Z doesn't hold a candle to any of my 3 analog scopes when it comes to X-Y mode and Lissajous figures.

author: oldway
author_rank: Super Contributor
timestamp: August 20, 2015, 11:54:47 am
content: Some analog scopes.Left top: Philips PM3233 10Mhz 2beamswith long decay phosphorLeft midden: Tektroniks 2235 100Mhz 2 channels 2 time basesLeft bottom: Philips/Flule PM3094 200Mhz 2 time bases, cursors, 4 channelsMid top: BBC Metrawatt M6004 100Mhz 2 channels 2 time bases rebranded Hameg HM1005.Mid Midden: Hameg HM 605 60Mhz 2 channels with delay and component testerMid bottom: Hameg HM1505 150Mhz 2 channels 2 timebases, cursors and component tester.Right top: HP1740A 100Mhz 2 channelsRight bottom: HP1725A 275Mhz 2 channels

author: amemic
author_rank: Contributor
timestamp: August 20, 2015, 05:07:42 pm
content: Quote from: oldway on August 20, 2015, 11:54:47 amNice collection, are you offering to donate that HM605?

author: oldway
author_rank: Super Contributor
timestamp: August 20, 2015, 06:49:27 pm
content: QuoteThat's my workhorse ...I was repairing analog scopes, that's the reason why I succeded such a collection...and they are not all on the picture !There are some people who think they are useless...they should donate their old analog scope !But it is not what happen...instead, it is harder and harder to find a cheap HM605 !

author: amemic
author_rank: Contributor
timestamp: August 20, 2015, 07:45:50 pm
content: They are not useless at all, and I don't think they will be anytime soon...Yeah that is true...Hamegs are really holding their price... :-D

author: tautech
author_rank: Super Contributor
timestamp: August 20, 2015, 08:02:07 pm
content: Quote from: oldway on August 20, 2015, 11:54:47 amNice collection.I thought you must have a strong bench.Then I enlarged the image to see the sag in your shelf.100 kg +?Put a support under the shelf Oldway, I would hate to hear that it broke one day.

author: oldway
author_rank: Super Contributor
timestamp: August 21, 2015, 06:15:39 am
content: It was only to take the pictureNothing wrong happened...I also have a tek 465B (working), a tek 2236 (not 100% funcional), another HP1740A (not working, for parts) and an HP1715A (not working, for parts)

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 22, 2015, 11:07:31 pm
content: What happened on this thread occurs more often than not is due to a specific individual(s) that hold the opinion that all analog CRT based real time O'scopes are utter outdated technology that should be relegated to the scrap heap or museum and the only time domain instrument worth using in these modern times is a DSO, no exceptions.Facts and the technical realities are both analog CRT & DSO have their place for instrumentation needs and those who are wise will have both using what meets the specific instrumentation needs best. To automatically and generalize that Analog CRT O'scope are all useless is quite blind and truly ignorant.What appears that has happened after the market wide acceptance and dominance of DSOs is the agent of the data box which essentially reads out and interprets the graphic display for the user in many ways relegating the basic skills of using a time domain instrument secondary.Over reliance of this data box and techno feature baked into the modern DSO can become a handicap beyond it's instant data presentation.IMO, learn the O'scope basics on a good analog O'scope. Once these fundamentals have been mastered and well understood, then move on to a DSO with a full understanding of it's limitations.There is just a HUGE amount of information available on a good high quality analog CRT based O'scope, problem is it takes skill, knowledge and more to fully utilize this information. Granted this display will not provide instant frequency measurement out to several digits of accuracy or display rise-fall time or amplitude to several digits of accuracy and all those signal chopped to bits advantages. This perceived advantage does come with many traps that users must be aware of or there will be more than a few hidden and user deceptive problems.Another very worth while read is Jim Williams Ap note# 47 for O'scope users Analog CRT or DSO.http://cds.linear.com/docs/en/application-note/an47fa.pdfBerniceQuote from: amemic on August 20, 2015, 10:18:40 am

author: oldway
author_rank: Super Contributor
timestamp: August 23, 2015, 06:35:57 am
content: In most applications, the accuracy of 5% of voltage's and rise time's measurements is sufficient.That is what is obtained with a calibrated analog oscilloscope.But for frequencies, this is often insufficient.Some oscilloscopes have an Y amplifier output for the A channel on the rear panel.This is the case with the Hameg HM605.I have a HP5315A counter plugged into the amplifier output Y so I have a precise measurement of the frequency.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 23, 2015, 07:12:50 am
content: 5% accuracy for amplitude and rise-fall time is often good enough. Unless the circuit involved absolutely requires extreme precision, most analog designs should work using 10% tolerance parts without difficulty. If they do not, producing them can result in a lot of problems.Amplitude, frequency, rise-fall time and all that is only the beginning of the amount of information available in the waveform display of a good analog CRT O'scope.The vertical channel out can be routed to a counter, Spectrum Analyzer, cascaded into the other vertical channel to increase gain trading off noise and BW and... (user beware as the amplifier output on most every instrument can have distortions & noise that can give false reading in instruments like a spectrum analyzer or ...)If greater accuracy is needed for these types of measurements. There are far better instruments to use like a hp 3403C thermal converter based AC voltmeter, RF power meter, frequency counter, network analyzer, impedance analyzer and...The traditional basic four items of electronics instrumentation would be Power Supply, Volt-Ohm Milliamp meter (digital or analog), Signal generator and O'scope. What appears to have happened in recent times is the heaping on of features into the modern DSO where it is trying to become time domain instrument, frequency domain instrument, signal source, precision volt meter, precision frequency counter and every other instrument all crammed into one box becoming Jack-Of-All-Trades, Master of None. This is not a bad thing in itself, but users MUST be aware of the inherent limitations when all this stuff is crammed into a single box of instrumentation.Mostly made possible due low cost reasonable performance to A/D and D/A conversion and lots of computing power with low cost memory, But it still has every limitation baked into a sampled data conversion system.One more item, most analog CRT O'scopes do not broadcast much RFI conducted or transmitted. I'm not convinced modern PC based instruments produce near zero RFI pollution into it's operating environment which might or might not be a problem.BerniceQuote from: oldway on August 23, 2015, 06:35:57 am

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2015, 09:16:20 am
content: Quote from: Rupunzell on August 23, 2015, 07:12:50 amThis view is only partly correct when you consider that even quite old CRO's use SMPS for the main PSU and HV, even older units also used SMPS for HV supply and the only CRO's that I'm aware that don't use switchers are some Hamegs.We often know by experience what frequencies to ignore and near field RFI investigation of TE will tell us what is not in Service manuals.The vast majority of TE is SMPS powered these days, it is something we must accept and adapt to.

author: oldway
author_rank: Super Contributor
timestamp: August 23, 2015, 09:31:55 am
content: QuoteThat's not right...they are sinus oscillators and not SMPS...You think they are flyback as TV's sets but it is wrong.NB: you have two kinds of CRT's:- for low cost, low frequency scopes (20Mhz scopes), you need only one accelerating voltage ( more or less - 2000V) which is generaly coming from the main transformer and voltage multiplier, with voltage regulating circuit.- for higher frequencies, (60 and more Mhz), you need a faster writing speed and a beam with more energy...for this reason, you have another accelerating voltage (PDA crt's, post deflection accelerating voltage) of 10 to 20Kv's.

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2015, 09:46:35 am
content: Quote from: oldway on August 23, 2015, 09:31:55 amThanks for the correction.But are they EMI free?

author: oldway
author_rank: Super Contributor
timestamp: August 23, 2015, 09:57:07 am
content: Quote from: tautech on August 23, 2015, 09:46:35 amAnalog scopes are not EMI free. I remember that there is a special military version of Tektronix 2235A with low EMI.But the HV oscillators works at low frequencies (more or less 30Khz) with little harmonics.Once, I repaired an analog scope who had a flyback transformer, same as those used in old TV's sets...I don't remember the brand, I think it was an Hitachi ...but that's the only one I have seen with a flyback transformer.Nb: if you intend to use your scope for repair, I recomand to buy a scope with component tester.Some analog scopes with this feature: most of the analog scopes of Hameg (not the HM1005), Hung Tchang OS-620...

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 24, 2015, 04:05:04 am
content: That remains strictly driven by measurement instrumentation needs.For the majority of folks working with digital and related systems and other switching centric devices, all that RF pollutions might be perfectly acceptable and not ever a factor.Then there are folks who don't work with much of any of that switching digital stuff resulting in this group of crusty curm-crone-Mudgeons, that hold on to their older non-digital centric instrumentation for their lower RF pollution and other technical aspects. The number of Silicone Valley companies that still have non SMPS powered instrumentation could surprise more than a few.As the "electronics" industry has become cyber-centric, energy efficient centric and generally software and data centric the traditional electronics industry has become much of a speciality. Yet the non digital-cyber-software-data centric areas of the electronics industry has not died off as most predicted. Instead it has grown in surprising ways.Newer is not always better, if is often just different. Those who are wise and experience will discard current fashion and focus on the specifics that fits the measurement and instrumentation needs best, not what is proclaimed as the latest and greatest. The flip side of this has much to do with marketing, capital equipment expenditures related to taxes and how the accounting folks will allow the engineering folks to spend company funds.BerniceQuote from: tautech on August 23, 2015, 09:16:20 am

author: Rupunzell
author_rank: Frequent Contributor
timestamp: August 24, 2015, 04:54:37 am
content: Hold a 10X, 10meg divider scope probe tip directly at the trace displayed on the CRT with the vertical amp set to it's highest sensitivity. What will be displayed would be the probe picking up the RFI streaming off the front of the CRT. This is another source of RF pollution. The common solution to this is to install a fine metal (often copper) screen that is connected to the O'scope's chassis ground in front of the CRT. This significantly reduces this specific form of RF pollution and enhances CRT display contrast.Many of the boat anchor Tek main frames used a resonant sine converter to produce the HV for the CRT. These have low noise and don't produce much RF pollution as they are pretty well shielded within the system and reasonably decoupled from the system power supply preventing this stuff from appearing at the AC power mains input via the power transformer and system ground.The Tek 547 has a very traditional transformer with regulator power supply with a resonant sine converter for the HV, this results in a low noise O'scope in many ways. Jim Williams did more than one app note on low noise HV converters and a video on just how low noise they can be when done properly. Just one of the many circuit lessons that is available from learning about the Tek 547.http://www.edn.com/design/analog/4348233/EDN-Access--03-16-95-Tripping-the-light-fantastic-a-case-study-in-circuit-desigBeyond boat anchor analog CRT O'scopes, there are a good number of boat anchor RF signal sources, power meters, spectrum analyzers and.. that features well shielded, low noise, low RF pollution to the system power supplies.BerniceQuote from: oldway on August 23, 2015, 09:57:07 amAnalog scopes are not EMI free. I remember that there is a special military version of Tektronix 2235A with low EMI.But the HV oscillators works at low frequencies (more or less 30Khz) with little harmonics.