YAOT: Yet Another Oscilloscope Thread - Tektronix 454 or HP 1720A - Page 1
Forum section: electronics / beginners

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 01:48:29 am
content: Hi!I'm new and looking for my first scope. On offer in my local area for seemingly fairly nice older scopes are:* Tektronix 454 for $50* HP 1720A for $75What are y'alls thoughts on pros and cons of each? Spec wise, the HP seems like the winner. However, it seems that documentation etc. is rarer for the HP, which is a little concerning. Also, owner of the HP is not an electronics person. On the listing, there's a trace that looks good, and they're willing to let me bring a probe and do some rudimentary testing (i.e. probe to the test pin). Tek on the other hand, owner seems to be an electronics person who upgraded and now no longer uses the scope.My goals are general hobbyist use, probably with a bend toward digital/uC work, mostly just to get the ropes of using an oscilloscope for relatively cheap and figure out what I want/need when going up to a digital one in the future. Plus these old analog ones are a real treat just to look at, imo

author: jmelson
author_rank: Super Contributor
timestamp: February 25, 2021, 02:01:11 am
content: You might want to spend a bit more and get a newer model. 454 is REALLY old, there are likely to be VERY few parts to be had, if you should need them. I would think on the HP, there will be NO parts available at all. A few years ago I got a tek 2465 and have been really happy with it. A scope is one of the most powerful tools you can have in electronics, you should treat yourself to a good one.Jon

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 02:16:18 am
content: As far as I've researched, the 454 is the last 400 series model they made without proprietary ICs, so repair parts should in theory be able to be had. The HP, on the other hand, may be more difficult in that regard.In any case, with this scope the goal isn't necessarily to be able to do everything... it's half to have something to learn with in the $50 price range and half for the vintage aesthetic sitting on my workbenchhahah

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 02:27:51 am
content: Also of note, there's a guy selling a Tektronix 7603 and 7854 with some 7 series modules (7A26, 7B71, 7A18, 7A13) which seem to be in working order... and it's honestly tempting just to have one of them, even though I know these things are definitely not a great choice in terms of a reliable primary scope... I mean how cool do these things look

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 25, 2021, 02:52:21 am
content: It's simple, do you want the scope to be a hobby in itself, or just a tool that you use?

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 03:26:50 am
content: A great question indeed.The heart says, "Don't care, gimme cool sh*t"...The wallet says, "Tool"

author: Electro Fan
author_rank: Super Contributor
timestamp: February 25, 2021, 03:34:55 am
content: Quote from: Alex Eisenhut on February 25, 2021, 02:52:21 amThis ^^ is well said. So it depends.Few things are as cool as a vintage oscilloscope, especially a Tektronix oscilloscope - including the 4xx, 22xx, 24xx and 7000 series; and sometimes at the higher end the bandwidth alone can be very useful. But after the bw and the nostalgia sets in sometimes so does the reality that from the 1960s - 1980s scopes didn’t leverage semiconductors as well as today - and therefore new scopes sold in 2021, even in the $300 - $500 range, can provide a lot more measurement functionality. So if you already have a digital scope or if you just want an analog scope as a hobby by itself or as a collector’s item, then a vintage analog scope might make sense. But for most (but not all) test and measurement purposes an investment in a modern digital scope is more likely to pay dividends in the pursuit of electronics as a hobby.On the other hand, if your budget (and bench space) is not constrained, and you have a line on a good working condition Tek analog scope - go for it. You might never get it out of your mind until you experience it and you might fall in love with it - and if you don’t or if you fall out of love with it you can probably resell it at break even plus or minus if it continues to work well (which it might).I had a HP analog scope, and have a 22xx, 24xx, and a 7000. They each do some things superbly and I prefer all the Teks to the HP. I wouldn’t recommend a 7000 as a first or only scope. If you have a scope collection underway, then sure add a 7000. If it’s your first scope I’d recommend whatever Siglent fits your budget.

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 03:48:12 am
content: Makes a lot of sense--thanks for the reply.My dilemma is... my budget is definitely constricted as of now. That sais, this would be my first scope, but almost certainly not the last. So, do I go with a 7000 series that's working as of now with the understanding that if it breaks down, I might not have the skills or tools (if another scope is required to figure out the problem...) to repair it yet, but use it as motivation to learn/acquire those skills and tools? Perhaps. I guess that's a question only I can answer for myself, hah.

author: bdunham7
author_rank: Super Contributor
timestamp: February 25, 2021, 03:56:35 am
content: Quote from: fu5ha on February 25, 2021, 01:48:29 amI buy, fix and sell old scopes as a hobby. Well, buy and fix anyway. And I can point out distinct advantages that some of them have over the newer, low-end DSOs. So I'm certainly not biased against them. However, what you are proposing would be like buying an old Model T as your only car "to drive for Uber and maybe run some errands as needed, perhaps a cross-country trip to see the relatives".Everything you are looking at is entirely unsuited for any type of logic or microcontroller work and you could work with an old analog scope for 20 years and still have absolutely no idea how to properly set up and use even a basic modern DSO. If you want one because they look cool and you want to play with one (and repair it extensively, no doubt) or even learn about how old analog scopes work, great! As long as you have plenty of space on your bench and no illusions of doing any practical work in the areas you mentioned, go for it.If you have space, go for the 7000-series mainframe ones after doing some research on the specific models. Those are works of art and you can get all sorts of interesting plug-ins. I've never seen a 7854, that might truly be interesting if it isn't broken. The 454 is just a really old scope.

author: george.b
author_rank: Frequent Contributor
timestamp: February 25, 2021, 03:58:06 am
content: Quote from: fu5ha on February 25, 2021, 02:16:18 amAs long as it doesn't develop a problem with the tunnel diode used for triggering. Replacements aren't very plentiful.Just something to keep in mind.

author: Electro Fan
author_rank: Super Contributor
timestamp: February 25, 2021, 06:13:48 am
content: Quote from: fu5ha on February 25, 2021, 03:48:12 amOk, 3 questions, and some thoughts:1. Is there anything super special rare about the particular 7000 you have your eyes on?If not, there will probably be another similar 7000 that will surface later. My experience has been that for every working plugin I have I also have approximately one plugin that used to work and is now a parts donor. I’d say that the availability and prices have held steady over the last few years; some things get more scarce but a few have become less expensive. In any event, you pretty much have to bet you will be able to get more plugins in the future to keep a 7000 running so maybe you can start in the future.2. If this isn’t likely to be your last scope, how long until your second scope is on the bench?Conceivably that’s when it would make more sense to go for a 7000 or other vintage scope.3. How strong are your diagnostic and repair skills?The stronger the answer to this the stronger the case for passing go and for starting with a 7000. The less strong the answer to this the stronger the case for starting with a modern scope and other test equipment on your bench before undertaking a 7000 preservation and regular use project.Net, net: I sense you are beyond a beginner with electronics. If this is correct and if you are feeling lucky and you have a line on a good deal on a working 7000, go for it. But if you are then going to look around for ways to use it while it luckily continues to run, you will probably pretty quickly realize that for the same price and a sixth the bench space you could have a Siglent or Rigol etc that would have a higher probability of turning on and operating properly every day, and that once on would do many more measurements that you would enjoy making and learning about.This has just been some reasoning toward the long answer. The short answer was Alex Eisenhut’s post.The good news is test equipment and electronics make for a great hobby (or profession) with a ton of fun learning opportunities, so you should enjoy the journey either way (vintage analog or modern digital). Enjoy the research and shopping as well as the acquisition and operation. The only other advice is that with a scope you are going for one of the tastiest chips in the bag, but if the first chip is even half delicious you are very likely going to be reaching into the bag for many more chips. Translated: think about your strategy and budget for all the test equipment that might be headed for your bench - it might influence what you buy in what sequence.

author: dzseki
author_rank: Frequent Contributor
timestamp: February 25, 2021, 07:09:41 am
content: I have a HP 1720A for years (ex-military unit). I am grown to it, but probably only because I've spent so much time (trying to) fixing itMy particular unit does not live up to its bandwidth specs, to be fair it is always exceeding ~240MHz. This is thought to be some oxidization process going on in the twinax delay line, as poking around the delay line helps on this somewhat -for some time at least.Besides this I have/had a long battle with some vertical instability (the line jumping up and down slightly), It went away for a year on its own, then came back. I went as far as changing the whole Y-output amplifier, that seemed to solve the issue again for a few years, but lately I can see it coming back again. So it is either a problem yet to found (tube?) or there is a structural weakness in the Y-amplifier.I've had an odd spring broken in the camshaft of the input attenuator, but hey this tool is passed 40 already...I can't pinpoint any particular or cool features of it though, all controls are as expected.I am using it for checking linear amplifiers with 100MHz+ bandwidth, and it is OK for me. Also my attachment to it may come from the fact that I also have a matching HP 1120A 500MHz FET probe to it..

author: rstofer
author_rank: Super Contributor
timestamp: February 25, 2021, 01:58:56 pm
content: Quote from: fu5ha on February 25, 2021, 02:27:51 amIt raises your geekism coefficient by at least an order of magnitude. If the assembly produces even a 50 or 60 Hz sine wave, you're in an elite crowd!

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 03:12:12 pm
content: Quote from: Electro Fan on February 25, 2021, 06:13:48 amThe 7854 seems like a pretty rare and also pretty awesome unit, which is half the reason it's tempting. The 7603 seems significantly less unique and less ultimately useful even when it is in working order. Also, according to the (admittedly small) amount of research I've done, the 7A13 module is also fairly rare and can be useful, though of course, I don't have anything directly in mind to use it to do so, ...Quote from: Electro Fan on February 25, 2021, 06:13:48 amI'm not sure, honestly. Ultimately knowing the way I work and spend, it probably just depends on when I find a project that actually requires me to have one (and if the one I get initially is no longer working or will just not do what I need it to do for that project).Quote from: Electro Fan on February 25, 2021, 06:13:48 amHmm... my diagnostic and repair/problem solving skills in general have always been very good, one of my strongest suits. That said, the amount of experience I have with doing diagnostic and repair with electronics on the level of something like one of these scopes is essentially zero. However... I have always learned best when I dive in the deep end and learn as I go with a specific goal/project in mind.Quote from: Electro Fan on February 25, 2021, 06:13:48 amHeh, yeah, I think I am fairly firmly into "intermediate" territory rather than a beginner.Quote from: Electro Fan on February 25, 2021, 06:13:48 amWell said! Thanks for all the advice

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 03:21:38 pm
content: Quote from: rstofer on February 25, 2021, 01:58:56 pmHahahah, well in that case...

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 03:22:37 pm
content: Quote from: dzseki on February 25, 2021, 07:09:41 amI saw a couple of your posts about it when I was googling haha! Thanks for the inputThe one I'm looking at is also ex-military.

author: rstofer
author_rank: Super Contributor
timestamp: February 25, 2021, 03:25:35 pm
content: You aren't really on an island when it comes to repairing these old scopes. Somebody over on the Test Equipment forum will have already solved the very problem. If not, there are manufacturer specific forums on the Internet and, for absolutely certain, somebody will know the answer. The answer may be to 'junk the unit' but that's not likely.Even the knobs have a value so even if you just part it out, it's unlikely you will lose money.I have an old Tek 485 that works fine. When it doesn't, well, it's out to recycle it goes. As nice as the 350 MHz bandwidth is, there is no analog scope that compares to the modern DSO.Something like the Rigol DS1054Z unlocked to 100 MHz is available brand new for $349 so it doesn't make much sense to invest heavily in an obsolete CRO.Unless repairing scopes is considered part of the hobby.

author: MarkL
author_rank: Unknown
timestamp: February 25, 2021, 04:09:46 pm
content: Quote from: fu5ha on February 25, 2021, 03:12:12 pmJust a note that neither of those two scopes you've pictured have a 7A13 module, in case you were looking forward to that functionality. Maybe the seller is supplying it separately?Here's what a 7A13 module looks like:https://w140.com/tekwiki/wiki/7A13There's a mechanical display version and an LED display version.

author: Electro Fan
author_rank: Super Contributor
timestamp: February 25, 2021, 05:13:42 pm
content: Quote from: fu5ha on February 25, 2021, 02:27:51 amHow much (with any shipping)?

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 05:28:58 pm
content: Quote from: MarkL on February 25, 2021, 04:09:46 pmYeah the seller is supplying it separately, I think they just put the 7A18 and 7A26 in there because they're the more common kind of vertical module

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 05:30:46 pm
content: Quote from: Electro Fan on February 25, 2021, 05:13:42 pmThey quoted the 7603 with all 3 pictured modules for $150, or the 7854 with no modules for $50... Think that could be negotiated a little bit at least, especially considering they're still on the market after a little over a month. I emailed to see whether they would be willing to sell the 7854 with the modules (I don't see why not, but they didn't put an asking price in the ad). Shipping $0, though I would be driving an hour and a half to pick it up (fine with me)

author: Electro Fan
author_rank: Super Contributor
timestamp: February 25, 2021, 05:38:33 pm
content: Those are pretty reasonable prices. The market generally sets the price and anyone who owns one (if they have been using it) likely is thinking it’s their near duty to make sure it goes to a new owner who will take good care of it and appreciate what it is and what it represents; such an owner might even care less about the price than finding a good new owner. Assuming the price for the frame(s) and plugins are all included (and maybe some probes, you will need one or two of those) and assuming it’s all working and the price makes sense, I think your answers indicate you should buy it. You will enjoy it for awhile and maybe forever and if you decide you need to free up the funds for something else you can sell it - which might cause someone else to find and read this thread, which will help your buyer take you up on your offer. Seriously, if it’s in decent condition and you can afford it give it a go. Worst case you will resell it and buy a Siglent, etc. Or maybe you will get the vintage Tektronix bug and try another model.Edit: typos fixed

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 05:43:55 pm
content: Quote from: Electro Fan on February 25, 2021, 05:38:33 pmThat's pretty much exactly what I'm thinking7854 here I come.... As soon as the seller replies, at least

author: Electro Fan
author_rank: Super Contributor
timestamp: February 25, 2021, 05:47:44 pm
content: Congratulations almost. Hope the deal works out well.Just remember it’s almost impossible to eat just one chip. You will want DMMs, a generator, and a bunch of other stuff if you don’t already have the stuff, and I think almost everyone here thinks you are still headed for another more modern scope. If you haven’t discovered TEA you should read up on it. Some people think 19 is Par for oscilloscopes.

author: rstofer
author_rank: Super Contributor
timestamp: February 25, 2021, 07:16:50 pm
content: You can increase your geekness coefficient even further if you have the roll-around cart. They show up on eBay from time to time. Usually with a scope attached... You would be reaching 'guru' status and everybody who saw the setup would forever hold you in awe.

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 07:32:34 pm
content: Quote from: rstofer on February 25, 2021, 07:16:50 pmhahaha

author: fu5ha
author_rank: Contributor
timestamp: February 25, 2021, 07:34:24 pm
content: This one went for 10 bucks! lolhttps://www.govplanet.com/for-sale/Shop%2C-Warehouse-%26-Consumer-Tek-Tronix-204-2-Scope-Mobile-Spectrum-Analyzer-Cart-Kansas/3142653/NSN/6625-00-224-2423

author: wizard69
author_rank: Super Contributor
timestamp: February 26, 2021, 08:40:45 pm
content: A scope can be an important investment for the test bench. The problem with old scopes is that they do in fact age and thus require more maintenance. This doesn't even consider the issue of parts. For starting out I understand why a $50 scope has huge appeal, so just buy with eyes wide open.While this opinion might be at odds with others but I'd rather see a beginner invest in a good multimeter when starting out. The reason is that even if interest slips or life distracts you, a DMM can be very useful around the house. You will have the knowledge to use it to repair, stuff in the house, the cars and other tools in the shed. It is sort of like having a set of screwdrivers and other basic hand tools that should be in every house.Now a year or so from now, if you have developed the knowledge, you will likely want a new scope. I don't see you having a long term relationship with these old scopes unless you get extremely lucky and get one in very good condition. On the flip side the whole process of keeping an old scope running is actually a good way to learn electronics repair. Sadly you might be in need of another scope to do those repairs.. Look at it this way at least you are not going as retro as the guy that does Mr. Carlson's Lab. By the way it might be worth considering reviewing a few of the YouTube videos for user "Mr Carlson's Lab" as they can give you an idea as to what you are getting into.So consider buying both scopes. Yeah that is a huge cost consideration.

author: Electro Fan
author_rank: Super Contributor
timestamp: February 27, 2021, 12:00:04 am
content: Yes, it makes sense to have at least one if not 2 DMMs before buying a scope. I'm guessing the OP already has one or two DMMs but if not, it would be wise to start with a DMM. This is why I suggested thinking about the overall strategy for building a bench/lab full of test equipment. I suspect that a signal generator, power supply, test leads/cables, etc. etc. will all be wanted and probably needed, not to mention breadboards, parts, tools, and you name it.

author: wizard69
author_rank: Super Contributor
timestamp: February 28, 2021, 12:26:55 am
content: Totally agree! I started in electronics with nothing and couldn't afford instrumentation and would have died if somebody gave me a multimeter much less a DVM. Things have changed a lot since then (the 1970's) and frankly access to equipment is far easier and I actually have money. I still put a lot of value in a quality multmeter and would suggest such to anybody starting out.It isn't that a scope is useless, rather they are very useful but also a big expense for somebody that may just be cracking the books and learning electronics. It can actually make sense in my mind to pick up a used and dirt cheap scope, to help with that learning process. If the person sticks with it, in a year or two they will want a better scope with all the features suitable for their interests. I know people like to knock old analog scopes and sometimes for good reason but I also think that many forget about the learning process.The other thing with DMM's is that the first one will not be your last. It is completely reasonable to have 2 or more and actually make use of them at the same time. It is actually hard to make a bad buying decision when it comes to DMM's because eventually you will need another one anyways. A scope on the other hand is likely to be the only one on a bench for a very long time, TEA sufferers excluded here.Quote from: Electro Fan on February 27, 2021, 12:00:04 am

author: fu5ha
author_rank: Contributor
timestamp: March 11, 2021, 05:05:57 am
content: Yep, already got two DMMs heheEnded up not getting either of these scopes, ultimately for logistical reasonsStill looking at possibilities though. Thanks for all the thoughts