Are old digital scopes worth it? - Page 1
Forum section: electronics / testgear

author: Axtman
author_rank: Regular Contributor
timestamp: February 25, 2014, 12:30:21 am
content: I bought a Tek 465 scope today. The guy that sold me the scope also had two older digital oscilloscopes for sale. These digital scopes are at least 20 years old, big, heavy and most likely green monochrome. I could not get a good look at them because they were up high and shoved in a dark corner. One appeared to be HP and the other Tektronix, but unfortunately I could not read the model numbers. So I am asking in very broad terms if older digital scopes are worth pursuing? Are digital scopes like computers where with the rapid advancement of technology that the computers are practically worthless in a few years.The 465, on the other hand, is 30 years old or more and real work horse and will not be outdated by new improved analog designs. The 465 will probably be around for another 30 years!Thanks!

author: Hypernova
author_rank: Unknown
timestamp: February 25, 2014, 01:10:17 am
content: If it's one of those 2k point garbage, no. Otherwise as long as you can get them cheap they are worth the space. I would only get something that old if there is something special about them eg, Tek had a line of scopes that had floating inputs or one of those handhelds that Dave took apart recently.

author: Maxlor
author_rank: Frequent Contributor
timestamp: February 25, 2014, 01:16:59 am
content: Congratulations on your scope! I thought myself about getting a 465 a while ago, but eh, I don't really need it, and it's bigI think it's a really nice model though. I particularly like the distinctive layout.Even old digital scopes bring one nice feature to the table: single shot captures, which means you'll be able to display stuff that happens very rarely, or even only just once (like after you press a button.)Of course, you might just get a newer DSO instead, which probably does a better job, and it'll be a lot smaller.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 25, 2014, 01:30:36 am
content: Some of the old digital scopes had a delayed time base so the sample memory was less important.If one of the digitals is like 2440 of better might be good investment.

author: EEVblog
author_rank: Unknown
timestamp: February 25, 2014, 01:35:56 am
content: Quote from: Axtman on February 25, 2014, 12:30:21 amNot really, unless it's "real-time" and has decent memory depth.e.g. I have a HP54622D that is still a very useful scope by modern standards.

author: Axtman
author_rank: Regular Contributor
timestamp: February 25, 2014, 01:39:15 am
content: Hypernova,What is a "2k point" scope?One of the scope, I think the HP, had 4 plug-ins. I am assuming that it was a 4 trace scope. I kick myself for not trying harder to get the model numbers. I might go back tomorrow with a flashlight and binoculars!If I am interested in it, I will definitely power it up and see that it passes all the self checks. Are their any other things that I need to look out for that would be deal breakers? I definitely do not need ANOTHER expensive door stop!Should I just save my pennies and buy a cheap Rigol digital scope?Thanks!

author: linux-works
author_rank: Super Contributor
timestamp: February 25, 2014, 01:51:50 am
content: if you have a 400 series tek scope, that's a great analog box.now get a cheap rigol for the digital side and you will have most bases covered.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 25, 2014, 02:11:18 am
content: As a general purpose scope, I don't mind my TDS460 (4 channel, 350MHz, 10kpt memory, though I normally have it set for 2k anyway). Main complaints: lack of serviceability, old caps (I had to replace all the SMT electrolytics), and slow menus (which is awful especially considering the contemporary HP 54600 series scopes all have instantaneous menu functionality). No doubt a direct result of the management shift in Tektronix around 1990 or whatever. I don't have any problems with the sampling performance. The display is green monochrome (with a 9-pinVGA output, oddly), no shades of "gray" so no antialiasing. Makes it hard to tell multiple waveforms apart, though that's arguably typical of anything before the advent of color.The main issues with a 465 or 475 are old caps of course (the multi-terminal electrolytics in the main supply are difficult to extract; the rest are tantalum which are either fine forever or obviously toasted to oblivion); used, worn or broken controls (attenuator, timebase, TRIG POL knob and switch, etc.); weak CRT (one or the other was apparently notorious for running the CRT heater a bit too hot, leading to relatively rapid fading; after about five years' solid use, my 475 was too dim to use, then I got a replacement CRT); and if you're unlucky enough to have other burned out components, some of them are a bit hard to come by (tunnel diodes being a good example), only available as replacement parts (which fortunately are still fairly well stocked by specialized suppliers, or as salvage from dead "parts-only" scopes).Tim

author: Hypernova
author_rank: Unknown
timestamp: February 25, 2014, 12:08:16 pm
content: Quote from: Axtman on February 25, 2014, 01:39:15 amSample memory size. Considering that modern Rigols offer memory measured by the meg's older scopes only values is if they got nice front ends and bandwidth.

author: David Hess
author_rank: Super Contributor
timestamp: February 25, 2014, 12:51:54 pm
content: I have a number of old digital storage oscilloscopes and I would say that they are worth it assuming you are prepared to perform maintenance on them.I would not get any though that lack peak detection which limits you to something newer than a Tektronix 2230 which is the oldest DSO that I know of which supports this important feature. When I went hunting for a DSO a couple years ago, the low end Rigol models lacked peak detection. They have envelope detection which they call peak detection but that is not the same unless you can set the number of envelopes to 1 like the Tektronix 2440 series can.Old DSO sample rates are not "real time" by today's standards but they support equivalent time sampling which largely makes up for it on repetitive signals. An old Tektronix 2230 (20 MSamples/Sec) or 2232 (100 MSamples/sec) have an equivalent time sampling rate of 2 GSamples/sec. The 2440 series has an equivalent time sampling rate of 20 GSamples/sec.The short record lengths are not a problem if you have delayed sweep. With modern DSOs, I tend to use the shortest record length anyway to get the fastest update rate.I have yet to crash one of my old DSOs and I cannot say the same for the modern DSOs I have used.The only feature that I miss on the old DSOs that I mentioned is variable persistence and having 4 channels but since the 2230 and 2232 are also analog oscilloscopes and I have several of them, that has not been a problem and I have other analog storage oscilloscopes which provide those features anyway if needed.