Old DSO vs analog scope - Page 1
Forum section: electronics / testgear

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 07:00:29 pm
content: I was wondering if there is real difference in usability of older DSOs and analog scopes?For example there is the HP 54503A which has a single shot bandwidth of 2MHz, but can do 500MHz on repetitive signals. This is considered quite bad these days, and is less desirable among digital scopes.Analog scopes (say Tektronix 2465) obviously don't have such limitation in bandwidth, but their usage is also limited to periodic signals save from a very few exceptions.Am I missing something here?

author: TiN
author_rank: Super Contributor
timestamp: May 04, 2018, 07:18:11 pm
content: I think your thread fits T&M forum section better.As of the question, I'd go for Tek 2465 instead. Getting ancient DSO scope just for name "DSO" makes no much sense here.

author: ferdieCX
author_rank: Regular Contributor
timestamp: May 04, 2018, 07:21:40 pm
content: That is not really exact, they are not limited to periodic signals.Analog scopes usually have Single Sweep mode and variable Hold-Off.You can see non-repetitive phenomena setting the Brightness high and observing a single sweep of it.Good analog scopes also have a delayed time base, that allows you to trigger after a delay time.For more and better information, look for the user's manual of the Tektronix 465.I used to repair PDP-11 boards using one of them.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 07:29:29 pm
content: Quote from: TiN on May 04, 2018, 07:18:11 pmYeah, I realized, but I can't change it... :/Quote from: TiN on May 04, 2018, 07:18:11 pmIn fact currently I have a HP 1720A (analog, 275MHz scope) and want more bandwidth. I just bought a deffective HP 54503A for cheap I think it will be fun to play with it a little, no drama if it won't work out for me...Earlier i had a Yokogawa DL1740 4CH 1GS 500MHz DSO, now that was something, but it had some serious reliability issues, so with heavy heart I sold it instead.

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 07:29:53 pm
content: If you have a non repeating random or sporadic blip signal that you can not see with your eyes at analog scope, and provided the digital single shot 2 MHz bandwidth is adequate to catch it, and you're in the middle of troubleshooting a really-really annoying problem, which one do you choose ?

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 07:33:17 pm
content: Quote from: ferdieCX on May 04, 2018, 07:21:40 pmSo what is actually considered repetitive signal then? For an analog scope you need the signal appear repetitively (even if not evenly) because one single sweep is not enough to observe anything to the naked eye...Hold off and delayed timebase -to my knowledge- are also standard on any DSO.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 07:40:23 pm
content: Quote from: BravoV on May 04, 2018, 07:29:53 pmYeah, this is what I am thinking as well, OK, 2MHz does not sound much, but I surely could not see a 2MHz single event signal on an analog scope, not even the tenth of it (let's forget the analog storage scopes for a moment).

author: ferdieCX
author_rank: Regular Contributor
timestamp: May 04, 2018, 07:49:01 pm
content: Periodic is not the same than repetitive. If you want to see a specific section of a complex repetitive signal, the Hold-Off and the delayed sweep helps to do that.Except for very fast signals, a single sweep is very useful. I remember myself repairing dead PDP-11/23 CPUs and using the single sweep.I adjusted the brightness high, covered the scope and my head with a piece of fabric, and pushed the Reset key of the PDP.You already have a very good scope. If you need to work with very fast, random signals, save your money for a good DSO.

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 07:58:38 pm
content: Just don't buy any old DSO, unless they're really-really dirt cheap, I mean the level you comfortably throw away without loosing your sleep.Agree with ferdieCX, its better to save the money, and look for a great value for money "NEW" DSO, even the mediocre ones are still much better than those old anchor boat DSO in term of bandwidth, capture rate and especially memory depth, cause now memory is very cheap compared to decades ago. Worst all of them use customized chips that once hit, its not economically to fix anymore and become a burden.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 08:07:57 pm
content: Quote from: BravoV on May 04, 2018, 07:58:38 pmI don't need any fancy features just raw bandwidthI bought this one:https://www.ebay.com/itm/132547177700My offer at 50USD was accepted, although the shipping was more than that. What caught my eye is the cal sticker...

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 08:13:09 pm
content: Wow .. with shipping and handling = US $92.02 + import charges (estimated) $30.47 to Hungary.Since you bought it already, I think all I can say is just wish you luck on the shipment and hope it arrives safely.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 04, 2018, 08:17:00 pm
content: Quote from: BravoV on May 04, 2018, 08:13:09 pmI am optimistic

author: tautech
author_rank: Super Contributor
timestamp: May 04, 2018, 09:14:44 pm
content: Quote from: dzseki on May 04, 2018, 07:29:29 pmYou can actually.As OP you will have a Move Topic button at the bottom left of this page.Beginners or Test Equipment would be best for this thread.Hope your new/old HP serves you well.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 04, 2018, 09:21:45 pm
content: The extreme end of this is probably something like the SD-4850,http://www.radiowrench.com/sonic/so02146.htmlwhich has a low sample rate (100kSps max), alternating acquisition/readout phases, slow readout (Y-t analog output!) and absolutely no frills (e.g. measurements). I was recently given one of these obscure units; they're actually pretty capable in hardware, certainly much more than you'd expect given the specs, but hampered by the slow CPU (it runs at less than 0.5 MIPS), common 8-bit data bus and single port 2k RAM, and lack of DMA or buffering.On a more functional level, there's the classic Tek TDSxxx bench scopes, which had modest sample rates (100s MSps) and bandwidth up to a GHz or so. The menus are slow, and ET sampling gets much much slower as you go up (my TDS460 can take tens of seconds to acquire a complete trace at 5ns/div!).HP546xx series scopes were quite nice to use, from what I've seen of the lower models at least (the '00 and '22, I think they were).I would suggest starting from there, either classic HP or newer most anything else. Avoid classic Tek. Probably avoid classic Rigol and other Chinese brands, too -- they took their time ironing out a good UI, and you're not saving much money getting an old one versus new.Tim

author: David Hess
author_rank: Super Contributor
timestamp: May 04, 2018, 11:36:25 pm
content: Quote from: dzseki on May 04, 2018, 07:33:17 pmMore recent DSOs lack a delayed timebase. This is often obscured in the documentation which may refer to some type of delay function which actually only operates within the existing record and is what Tektronix used to call horizontal magnification. A good way to determine this is lack of trigger after delay capability.Long record lengths are not a complete substitute for delayed sweep or acquisition. Try measuring the pulse to pulse jitter of a one pulse per second output from a GPS with a long record at the maximum sampling rate of a DSO. 1 Gsample of memory would be required to achieve 1 nanosecond resolution although some expensive DSOs have ways to do this without a long record length.Quote from: BravoV on May 04, 2018, 07:58:38 pmThe issue here is that the old DSO being discussed has a bandwidth which would be very expensive in a new instrument. While equivalent time sampling rate can make up for real time sampling rate on periodic signals, nothing can make up for low bandwidth.I really think there is a market for high bandwidth low sample rate DSO but nobody makes such a thing.QuoteThis is not any different between new and old DSOs except in some unusual examples where complete documentation is provided. Any customized ICs or hybrids are usually the most reliable parts.Old ETS DSOs which had high bandwidth but low sample rate were used in semiconductor characterization and automatic test applications where their low sample rate and high generation time were not disadvantages. They were not intended for single shot applications except at the lowest frequencies. They are still useful especially for their high bandwidth for general purpose development within their limitations. They often had more than 8 bit resolution. They usually *lack* peak detection which is what I consider their biggest disadvantage.The Tektronix 7854 (400MHz 1MS/s 10bits), 11201A (400MHz 20MS/s 9bits), and 11400 (1GHz 20MS/s 10bits) are good examples of early DSOs like this.

author: bd139
author_rank: Super Contributor
timestamp: May 05, 2018, 08:17:56 am
content: Quote from: dzseki on May 04, 2018, 07:00:29 pmHP’s 546xx series are a pretty good compromise between the two. They are smaller than analogue scopes, have all the automatic measurement features of a DSO, usability of an analogue scope and no bugs at all. Considerably less cranky than the 54500’s too. Also some have limited 2 extra channels. Single shot is “variable” depending on the exact model but otherwise pretty good scopes. 90% of measurements I do are repetitive, the rest are usually very slow single shot so it’s a good compromise.Can’t beat the UI speed of the things either. Measuring rise time:https://youtu.be/56HZqPZpXJQ

author: precaud
author_rank: Frequent Contributor
timestamp: May 06, 2018, 03:04:57 pm
content: Quote from: bd139 on May 05, 2018, 08:17:56 amSame here. For the last couple months I've been using either a 54503A or 54510B while I figure out how to make room (physically) for a Lecroy 9450A in my setup. I really like the comprehensive self-cal and user interface of the HP's. Very fast. In this time I have yet to need need single-shot sampling faster than 20MSa/sec, so the interleaved sampling is fine.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 08, 2018, 08:09:30 pm
content: Thanks guys for the good advices!

author: dzseki
author_rank: Frequent Contributor
timestamp: May 15, 2018, 08:58:34 pm
content: Quote from: BravoV on May 04, 2018, 08:13:09 pmThe scope showed up today, it was DOA, but since it was sold as deffective, this was not surprizing at allIt turned out the mains connectors (both side) had severe oxidization on two pins (spark-overheat), also one of the line fuse was blown, for some reason it was rated to only 0.5A while it should have been 3A type.After scartching somewhat the connector pins and putting the right fuse it became alive, I got trace on it, and it appears to be passing the self tests. Although I did not put any signal on it just yet. The Dallas chip was replaced already, not brand new (2010 week 13), but much better than the original.Now I want to make the mains input connector properly, also as I've read the Schaffner filter should be replaced as well.

author: joeqsmith
author_rank: Super Contributor
timestamp: May 15, 2018, 11:49:22 pm
content: Quote from: dzseki on May 04, 2018, 07:00:29 pmHope you are enjoying your new scope. I had given one of these old scopes away a few years ago and a couple of weeks back a friend of mine ships me one of these relics with some parts. I spent a few days doing repairs. The oldest is a 68000 VME chassis. The one plugin can run 1GSs singleshot, 2 channels or 2GSs interlaced. It does have 2 channels with a 4GHz BW but as you describe for repetitive signals. They are big, heavy and dissipate a several hundred Watts. Still not a bad scope for the age.https://youtu.be/7SByDsNaYiA?t=1445