Tek 475a vs 2465 vs HP 1725 - Page 1
Forum section: electronics / testgear

author: DAIRVINE
author_rank: Contributor
timestamp: March 24, 2015, 06:01:31 pm
content: What are the relative benefits of old (affordable) high bandwidth (>250MHz) scopes, which would you recommend?Have I missed any?Are any of the old, now affordable, digital scopes worth considering?For a professional design engineer, setting up a home lab?I want an analog scope to use for the long term, and am happy to maintain it when it goes wrong.Beginners should probably look at 20MHz Hamegs.

author: PaulAm
author_rank: Frequent Contributor
timestamp: March 24, 2015, 10:51:32 pm
content: First, everyone is going to tell you to buy a Rigol. Buy a Rigol. Fine, that's out of the way.I favor Tek scopes of that era, so I'll pass on saying anything on the 1725.Both the 475a and the 2465 have custom Tek parts. Whichever one you get, I'd get a parts mule as well. The 475a is older and the filter cap rot is common, but is, I think, a much simpler scope. The 2465 has measurements and is much more complicated inside. The smd electrolytics rot the circuit board and you should plan on replacing every one when you buy the scope. Tantalums die as well and can take out the power supply (that happened to my 2432a). The u800 failure can turn it into a brick. They are essentially unobtainable and there's a low success rate of repair by baking. There has been some work on engineering a replacement using smd parts, so it's not totally hopeless.If you want simple to repair (and for any scope of that bandwidth, simple is a relative term), I'd go for the 475a, probably with a DM piggyback because I think they look cool. If you want the ultimate Tek analog scope with all the bells and whistles, go for the 2465.For a slightly larger (haha) form factor, you can go with the 7904 or 7904a a 500 MHz mainframe and have fun collecting plugins.

author: MadTux
author_rank: Frequent Contributor
timestamp: March 24, 2015, 11:36:23 pm
content: Get a 150MHz Tek 454A if you want a scope that you can service even after nuclear war. No custom Tek parts, except CRT and tunnel diode for trigger.Apart from that, I'm big fan of Tek 7000, so get a 7904(A), or 7704A. Wouldn't buy a 2465, for reasons mentioned.

author: EEVblog
author_rank: Unknown
timestamp: March 25, 2015, 12:35:56 am
content: Quote from: DAIRVINE on March 24, 2015, 06:01:31 pmGenerally not, no. usually limited memory, and they are physically big and generally clunky to use.QuoteWhat DSO do you have?If you have a decent modern DSO (and you should!) then you almost certainly don't need the analog scope.If you don't have one and have some money to spend then forget about analog scopes and old digital, go by a new modern DSO with intensity graded display.QuoteTek's are not know for their ease of repair using common parts. Even the ducks guts 2465 is now 25+ years old.

author: Electro Fan
author_rank: Super Contributor
timestamp: March 25, 2015, 12:44:21 am
content: Well, +1 for what Dave said, his answer is pretty “net, net” and it’s good advice, of courseAlso, +1 for PaulAm's comment: everyone is going to tell you to buy a Rigol; it might be a bit of an exaggeration but probably not by much; we'll see....If you want more background thinking on why, here are some more thoughts.It sounds like what you would really like is a used digital scope with about 250MHz or more - it's possible you will find an Agilent or something else that will fit your needs - but scope technology is advancing pretty nicely so it kind of depends on what features you want in addition to the bandwidth. You also mention you are thinking about an analog scope for the long term and you are up for maintaining it as needed. So, as a pro you might be looking for more bandwidth than typical entry hobbyists but like many home users you sound a bit on the fence about an analog vs. a digital scope - which is a very common first home scope question or trade-off. What you haven't shared is your budget... that would help people give you better advice.Without a doubt, Rigols offer excellent value. I happen to have a Rigol DS2072 and I have to admit if I could only keep one scope I'd probably keep the Rigol - but I would be very sad about giving up my Tektronix scopes. My first scope was/is a Tek 2247A and it is an excellent scope if you can live with 100 MHz. If someone is just getting started with electronics I think they can learn most of the basics with a 100 MHz scope. But of course if you work on something that needs more bandwidth, well, that amount of bandwidth becomes your requirement.I also happen to have a 2467B which I wanted for a long time but didn't "need" - but a very clean unit showed up and I couldn't resist. It is supposed to be the mother of all Tek portable scopes. Occasionally, when I run into something that needs more than 100 MHz but less than 400 MHz (although I think it might go higher) it is handy to have (vs. the 2247A) and for some measurements the controls and onscreen displays on the 2467B are nicer than the 2247A, but in some respects the controls and onscreen displays are nicer on the 2247A than the 2467B. The 2267B uses a measurement menuing system that requires you to go a few button presses deep and in the process to get some measurements it will reset the signal on the screen to parameters it chooses. This takes a few seconds and is sort of annoying. On the 2247A you can get various measurements easier. This is not a knock on the 2467B (it has lots of good/excellent performance and features) but I think it's worth looking at the 22XX series as well as the 24XX series. (There are many old Tek analog models to choose from - I'd recommend studying them closely before jumping on one unless you want to accumulate several.)I don't have a 4XX series and the I have thought about looking for a 475 or maybe a 485, but after experiencing the 2467B I have realized that the user interface isn't equal among all Tek scopes and I think both the 22XX and 24XX scopes are likely to have better user interfaces than the 4XX series, on balance, overall. Take a look at photos of 4XX screens in use - not much in the way of readouts (it's hard to even find a photo showing Time Division or Volts settings, much less cursors or frequency counters or rise and fall time, etc, etc.) Now, I'm sure someone will say "duh, if you need the Time Div or Volts values just look at the knob settings - and you can measure anything you want by examining where signals cross graticules". This is true but it's an incremental path and as you start to use the analog scopes with better UIs you start to appreciate the ease of use, speed, and general accessibility of various features and measurements.If you continue on this path you will find that even the top of the 22XX and 24XX series don't offer as many features and especially measurement capabilities as an entry level Rigol - and they definitely won't be as helpful when capturing (or playing back) a signal that is hard to trap. (Having said that, there are some feature exceptions such as intensity grading and others where the old Tek scopes will do things better than a Rigol - so it's not all clear cut apples and apples. On the other hand, a new scope with a warranty might have some advantages over a 20-30 year old scope.)Perhaps most importantly, when you cross over from an analog scope to a digital scope you get the ability to capture signals that would be difficult if not impossible to capture with an analog scope. If you want to make a single shot capture on a digital scope it's easy, with the analog scope not so much. If you want to decode signals, look at simple FFTs, and in general measure lots of signal attributes with onscreen displays a digital scope will be easier to use and just plain more functional.A Rigol will take up less space than an old analog scope - and it will be much easier to move around on your bench or take to another room/lab. This is not to say you shouldn't get a vintage Tek, but if you are on a limited budget or aren't sure how much you are going to really get into using a scope - and especially if you aren't sure you are going to want TWO scopes, I'd say start with a Rigol (or some other digital scope) and if you still have a desire for an analog scope, without a doubt, get a Tektronix next. I love my Tek scopes (I also have a 7904), but they are more nice to haves more than need to haves. FWIW, I also have a HP 1743A. From a nostalgia point of view it's ok, but I'm glad I only paid $40 for it. I definitely wouldn't keep it over any of the Tek scopes. (Someone on the forum, maybe more than one person, once said, for scopes buy Tektronix - for everything else buy HP.)Long story, short some people will say buy a digital scope, others will say buy an analog scope, and others will say buy both. I'm in the both camp but I'd start with a digital scope and then see how much you really want a second scope. Depending on the models you could have one of each for less than $1k total and maybe about $600 or less, but I'd spend the first $400 on a Rigol, or possibly more depending on which Rigol meets your needs. If you happen to find an older DSO from a company you admire you might be able to get more value out of a used DSO but if you are on the fence, get a new Rigol. Once you are pretty sure you are going to spend around $1k or more you might find some used (or new) DSOs that offer more value than a new Rigol. Up to about $1k, it's easy - just buy a Rigol.EF

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 25, 2015, 03:41:03 am
content: Buy a Rigol.What? someone had to.

author: Electro Fan
author_rank: Super Contributor
timestamp: March 25, 2015, 03:45:13 am
content: Quote from: Alex Eisenhut on March 25, 2015, 03:41:03 am

author: DAIRVINE
author_rank: Contributor
timestamp: March 25, 2015, 10:49:03 am
content: Thanks for the excellent advice, especially Electro Fan.At work I had:Picoscope 4224. I liked the storage buffer and 12 bits and big PC display, disliked the 20MHZ bandwidth and deaf periods and the limited input controls.Lecroy 300MHZ DSO Waveace 2034(I think). A good scope but limited storage buffer. Somehow I never liked using it.Tek 2225. Much nicer to use and I had more confidence in what it showed me, but then I have long familiarity with Tek scopes and disliked every other scope I used.A logic analyzer: This was better for some tasks like decoding serial signals. I once had a major glitch with an AMD 2900 bit slice system, and a logic analyzer in the end was the tool that fixed it.I started out at work with an old valve Tek storage scope, which was a joy to use, but very slow.Mostly I used the Picoscope, but would switch to the Tek or the Lecroy or logic analyzer for some tasks.Now a fast analog scope and a streaming DSO seem sensible. The DSO should preferably have 12+ bits and no deaf periods and a large PC display and better input conditioning. Sort of an improved Picoscope. Oh, also need to constrain the budget until I am earning better money. When are the Chinese going to do even an 8 bit USB3 streaming scope?I think a 475/1725 scope and a cheap logic analyzer may be my best combo until funds are improved or I need something better.Measurements?? Very nice and helpful, but most of the time analog accuracy is close enough. I would anyway use a timer counter for accurate frequency and a meter for accurate voltage.

author: HiTech
author_rank: Regular Contributor
timestamp: March 25, 2015, 01:25:33 pm
content: I can't speak on a Rigol from experience but I own a Tek 475A and a couple of their 22xx series as well as an HP 1741a. The HP by far is the easiest to service and relatively less parts inside. Far less than a Tek! The Tek traces are crisp but I still think the HP trace edges out the Tek and the HP scope is intuitively easier to use. Some of those Tek models used incandescent lamps to illuminate panel indicators and can be a chore to replace when they burn out, whereas the HP uses leds. Both the little DMM modules that attach to the Tek and the HP are dicky little meters IMHO! I think they are offered by Tek & HP more as being a convenience item. I have a LeCroy and you don't want to take off the cover cause the amount of circuitry in there will make you cry for your momma.

author: McBryce
author_rank: Super Contributor
timestamp: March 25, 2015, 01:28:28 pm
content: Although the 2465 uses a lot of custom parts that are difficult to replace when it breaks, how often do they really break? I bought my 2465 in 1996 (Secondhand). It's used about 6 to 10 hours a week since then. It's never had the caps swapped and it's still going strong today. Despite owning several M/DSOs, I still prefer to use it for certain measurements, although I know the DSOs would be well able to do the job. It's just out of habit and the fact that I don't have to keep going into menus to change settings. I wouldn't sell it for anything. I recently had the opportunity to have it calibrated for free (it hasn't been re-calibrated since i got it) and the guy returned it and told me that nothing needed to be adjusted! They don't make them like that any more.McBryce.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: March 25, 2015, 04:53:10 pm
content: More specifically, what will this O'scope be used for?Over time, it is apparent the modern DSO is designed and intended for high speed digital or pulse work with good computer interface capability. All fine and great if that is what the task requires.After thinking about this for a while, where high performance CRT based analog scopes continue to do well over their DSO counter parts is in analog design.Before getting into that, the difference between the Tek 475 & 475A. Tek 476 has 2mV vertical sensitivity, 200 Mhz BW @ -3db and will trigger well past 200 Mhz. The 475A has 5mV vertical sensitivity, 250Mhz BW @ -3db will trigger well past 250 Mhz. Both have less than nice trace definition as with the 465 and 455. Most common problems with 475 & 475A, fans wearing out, noisy rotary controls, noisy switches, tunnel diodes in the triggering can be difficult to get and the custom ICs are a modest problem as they are shared in other tek O'scopes. This tek family served as the basic industry work horse for decades and has a proven service, reliability and durability record. Having owned and used 455, 465s, 475, 422, 453, 454, 485. The best performance and nice to use is the 485 and difficult to fix for a host of reasons. The 454A is the sleeper in this group as it has nice trace definition, limited speciality parts and well made. It uses a distributed amplifier for the CRT and quite user fixable. If 150 Mhz of BW is acceptable this would be the one.Not interested in the Tek 2200 series a these were low cost lower performance O'scopes. Moving on to the Tek 2400 series, the 2465 & 2467 are the ones to have despite their speciality custom ICs used, dying capacitors in the power supply and all those things that are know to happen to them. The 2400 series has more BW than the 475 with better trace definition. Tek address this problem after SO many customer complained about it. The 2467 has a micro channel plate CRT which makes a BIG difference in viewing short duty cycle events. The two Tek portables here are the 485 & 2467 both of which is not used often as overall, I'm not a fan of portable O'scopes. Tek 7104 remains the daily user for analog design, discrete device analog design, few if any ICs. Here is why.The Tek 7000 series simply has better real world performance over the tek portables even if this does not appear to be the case on the spec sheet. There are things like vertical channel over drive recovery, triggering and more that are not on the spec sheet that might matter for a specific application. There are the host of plug-ins that go into the 7000 which makes them very useful. 7A22 delivers 10uV per box sensitivity with 120db of CMMR and DC offset in differential mode. The 7A13 has 1mV per box sensitivity at 100 Mhz, with over 40db of CMMR at 20Mhz. Over drive recovery is to within 2mV in 1uS with a +/- 10Volt over drive and built in voltage reference comparator. This is much the same performance as the LeCroy-Teledyne-Preamble 1820/1822 differential pre-amp add on and this list goes on.Has anyone carefully looked at what might be coming out of the inputs of a DSO and how their switch mode power supplies are broadcasting into the air and grounding?Why the analog CRT over DSO for high performance analog design. Analog design does not have a real need for absolute time base accuracy or vertical accuracy as analog stuff is dealing with all the values between 0 to 1, not 0 or 1. The real put-off for most is learning how to interpret what is on a CRT display. It takes years to decades of using a good CRT O'scope to fully understand and interpret what is on the display and how the test set-up and DUT has affected the displayed information on the CRT. Growing up during my early teens, trying to figure out the meaning of what was on the CRT display was a steep challenge on that Dumont recurrent sweep O'scope. With that, having the numeric displayed to the 0.00000xxxx digit or time and amplitude actually holds less meaning for this analog stuff wave shape fidelity can matter much more. This is quite the opposite for high speed digital stuff where timing accuracy, glitch capturing ability and related details really matter and the small swiggles on the waveform are mostly insignificant. As for BW, rise time response appears to be the primary factors driving the need for BW which is driven by high speed logic. Consider the time domain instrument requirements for Ghz data eye patterns -vs- amplifiers that work with sub nanovolt signals well below 1 Mhz.Push button numeric information instrumentation is not a substitute for real world instrument skills or interpretation of data.Bottom line, it really depends on application. There is no single ideal instrument or O'scope.BerniceQuote from: DAIRVINE on March 25, 2015, 10:49:03 am

author: Electro Fan
author_rank: Super Contributor
timestamp: March 25, 2015, 05:38:28 pm
content: http://w140.com/tekwiki/wiki/454"The 454 is the fastest general-purpose Tektronix scope that does not use proprietary hybrid circuits or proprietary integrated circuits....The 454 was introduced in March 1967. The 454A was introduced in 1971."

author: DAIRVINE
author_rank: Contributor
timestamp: March 26, 2015, 09:13:54 am
content: Quote from: Rupunzell on March 25, 2015, 04:53:10 pmThis post helps clarify things for me.Even digital design does not need the precision or measurements because its easy to count clock cycles and mostly the volts are low or high.Anything critical like frequency or harmonics/distortion or noise really require specialist instruments.So measurement features are a convenience but I would rather have the good inputs and bandwidth of a traditional high end analog scope.I will look at the 7000 series and 454 and 485.

author: Michaela Joy
author_rank: Contributor
timestamp: March 27, 2015, 08:21:39 pm
content: QuoteThat's -exactly- the same conclusion that I came to. I've been shopping O'scopes for about a year now. I finally decided to go for Tektronix, simply because the price was jus not beatable (2465B,400mhz in working condition for $325 usd) For what this scope offers, I don't see myself needing to buy a scope for a while.And, like Rupunzell said (roughly paraphrased): "What are you using it for?".I'm not using it to count missing pulses or decode protocols; I have a logic analyzer for that. And I'm not knocking Digital; It has its' purpose. You don't belittle a screwdriver because it can't drive a nail into a wall. But the price versus performance placed DSOs outside of my budget.My advice to You is this: Determine what you want, then, determine what you can afford. Then, shop like crazy until you find something in-between.Hopefully, when the dust settles, you'll be happy with your purchase.:MJ

author: DAIRVINE
author_rank: Contributor
timestamp: April 07, 2015, 07:09:03 pm
content: In the end I bought a (faulty) 475A for £55 and now its working I am really pleased with it. Of course then a working 2467B came up for £350, but it was a lot more expensive and in the end I decided it was not enough of an upgrade for me and my money was better spent on some RF test gear and, when required, a DSO.The 475A triggers really nicely, as every Tek seems to. It can display my maximum frequency of 480MHz fine(on 1ns/div), but triggering is a bit delicate and jittery at this frequency(even from ext and adjusting the timebase, but a sync pulse makes a nice stable display). The display line is a bit thick, which seems to be a universal complaint. The DM44 is basically a waste of time, maybe slightly improved time resolution, but not very useful. I could not find a schematic, so used a 475 schematic to fix it, which worked for the power supply capacitors. If you have a schematic for the 475A please can you send me a copy?

author: tautech
author_rank: Super Contributor
timestamp: April 07, 2015, 07:54:44 pm
content: Did you not find Service manuals?http://elektrotanya.com/tektronix_475a_oscilloscope.pdf/download.html

author: woodchips
author_rank: Frequent Contributor
timestamp: April 07, 2015, 08:39:35 pm
content: I have to agree with rupunzell, the Tek 7000 series are nice. Large, but if you have to try to repair a portable scope with everything crammed in then size is nice. I have 2445s, 485s, a 1725 and other analogue scopes, but none working and can't face delving inside. Also a Fluke 125, Tek 422 and other digital scopes but the knob twiddling and button pressing makes me scream after a little while. The cursors are nice, but I can count graticle lines, no use for FFTs and similar.On a slightly connected note, I am trying to understand oversampling and how an 8 bit ADC can do 12 bits, see other thread, which seems somewhat of a lie to me. But, that is still work in progress. The point is that I have seen others say that the modern DSOs use this oversampling, is this so? Can it be proved to work or not?

author: DAIRVINE
author_rank: Contributor
timestamp: April 08, 2015, 09:25:55 am
content: Quote from: woodchips on April 07, 2015, 08:39:35 pmIf you have an 8 bit ADC and add noise to the signal, you will get a random mix of adjacent levels. If you then average you can get a higher resolution. You need repetitive signals and it does work, but real 12 bits is much better. Also this assumes that signals are below Nyquist frequency.

author: JuiceKing
author_rank: Regular Contributor
timestamp: April 08, 2015, 10:06:35 am
content: Quote from: DAIRVINE on March 24, 2015, 06:01:31 pmI have a Tek 2467, 475A, and 7854--which I got in that order, the latter two being irresistible bargains. If I had to choose one, it would be the 7854 for its incredible versatility and the abundance of plug-ins that are cheap to ship. Footprint is not so much greater than the portable scopes, to tell you the truth. But the 2467 sees the most use because it's easy to use, has cursors, and the bright MCP trace works wonders on delay trigger. The 475A sees zero action.I also have a Rigol 1102E, which I rarely use. I would avoid DSOs that use one vertical control across multiple channels. Lots of button pushing and control errors for me.- Ken

author: dom0
author_rank: Super Contributor
timestamp: April 08, 2015, 05:35:33 pm
content: Quote from: DAIRVINE on April 08, 2015, 09:25:55 am*Scratches head* oversampling to get to higher resolution by means of decimation works just fine and can't be distinguished from the data an equivalent converter would yield. It doesn't give you a better converter, of course. It just reduces DNL and effective bandwidth / sampling rate and gives you more resolution. INL of course stays the same. Oh, and it of course requires at least one LSB of uncorrelated noise, but that's usually not a problem.

author: Rupunzell
author_rank: Frequent Contributor
timestamp: April 12, 2015, 04:54:55 pm
content: Averaging only works to improve accuracy if the signal under test is absolutely identical in every parameter over time AND the data acquisition system can nail this data with absolute precision with each passing acquired data set. Otherwise, the acquired data will be slightly different with each successive data set which adds errors.Over sampling is often used to interpolate additional points of date between the original points of data. This does not add any resolution to the original data set, it does make the process of filtering easier and allows other filtering options.Greatest accuracy is achieved by acquiring the greatest number of bits with the very best possible timing at the system input. Once that data set has been acquired, everything must be done to preserve data integrity or accuracy will degrade.BerniceQuote from: DAIRVINE on April 08, 2015, 09:25:55 am

author: dom0
author_rank: Super Contributor
timestamp: April 12, 2015, 07:32:08 pm
content: Oh dear! Now we're really mixing up everything, muddying the waters.Oversampling itself does, of course, not change the resolution of the resulting data words, it obviously can't do that.Oversampling and then passing the data through a decimation filter does change both resolution (up) and word rate (down).It is a perfectly fine technique, as I explained earlier, but requires the usual Shannon restrictions. (This technique is used _extensively_ in many ADC/DAC architectures of the last few decades, including the great majority of D/S converters.)Now, about averaging. We're talking about very different things here. A weighted moving average is for example a simple digital low pass filter, and, again, is a perfectly fine technique.I think you meant averaging as in waveform averaging as in how the DSOs do it. They do a point-for-point average of multiple acquisitions (trigger events), completely different story, has nothing to do with shannon converters. And yes, for waveform averaging many factors are very important such as trigger jitter and stability, signal repetitiveness and so on.QuoteTautology club?