Did I buy a decent oscilloscope? - Page 1
Forum section: electronics / beginners

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 12:13:04 am
content: Greetings,I just bought a used Tektronix 2246 100MHz from eBay seller alltest_instruments. The total with shipping and tax was $187.18.I only have some limited experience with a 20MHz scope and the one thing that I noticed was that the Tektronix might have some issue with the screen. But I do not know if it's an issue, I just see that the CRT behaves differently than the 20MHz scope.So, if I keep a trace in place for 5 seconds or so, and then I move the trace up or down, there is a faint ghost image of where the trace was, prior to moving it, that takes a second or two to fade away. Nothing is burned into the screen. It just that the phosphors that were lit take a little bit of time to fade.I tried to take a video and am posting a still to kind of show what it looks like. But things do look different on a picture.It doesn't really bother me. I just want to make sure the CRT is not at the end of it's life. I can vary the intensity of the trace from very faint to very bright, though.Thanks...

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 22, 2020, 01:00:48 am
content: It’s the persistence of the phosphor, a necessary thing in an analog scope.It’s scanning the crt in real-time so with the time base at its minimum 20ns and the x10 function on, that beam is wizzing across the crt in 200ns. If not for the persistence of the phosphor, you’d never see the trace. Keep the trace as dim as you can reliably see things and that’s as good as it gets.It was a very capable service bench scope thirty years ago. It’s fine until you need to look at one time event waveforms and then you realize today’s digital scopes are far more capable without the size, heat and most times, the noise.

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: May 22, 2020, 01:37:54 am
content: A scope needs to show a trace even at very slow speeds so uses a phosphor coating with a long time lag.If it didnt you wouldnt be able to see slow waveforms.

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 01:44:18 am
content: Definitely thank you for your replies.One question, tough. How come this is not how the CRT on my 20MHz scope behaves? Is it because it uses a different scan rate?Thanks...

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 22, 2020, 02:32:25 am
content: Yes, different write speeds and different phosphor persistence.http://w140.com/tekwiki/wiki/PhosphorBe sure to download the user and service manuals if you haven’t already done so. You might have to search a bit for the service manual but they’re out there.

author: tautech
author_rank: Super Contributor
timestamp: May 22, 2020, 03:56:34 am
content: Quote from: Adinol on May 22, 2020, 01:44:18 amReduce the trace Intensity and the trace persistence is much reduced.Like with any CRO use just enough intensity and no more.

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 03:58:38 am
content: The 2246 is a nice scope - I've had mine for close to 20 years now.As for the persistence, that's normal for the scope. Different scopes use different phosphor formulations, so comparisons between very different models are next to meaningless.Congrats on getting it, and enjoy your new gear!-Pat

author: james_s
author_rank: Super Contributor
timestamp: May 22, 2020, 05:44:45 am
content: Quote from: Adinol on May 22, 2020, 01:44:18 amDifferent phosphors have different characteristics. There are at least 3 or 4 different ones that were commonly used in scopes, each has different tradeoffs of brightness, visibility, writing speed, persistence, durability and other factors. Many Tek (and other brand) higher end scopes had several optional phosphors available as an option at the time of purchase. Probably the most common special order was the blue one optimized for use with scope cameras.

author: Electro Fan
author_rank: Super Contributor
timestamp: May 22, 2020, 06:50:16 am
content: Maybe post some more photos showing various signals and some of the readouts. The 2246 is a very nice model. It’s an analog scope but it used digital technology to display a fair amount of measurement info. Try the cursors if you haven’t already.

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 01:04:25 pm
content: Thank you all for your replies.The most important thing is that the CRT is in fact behaving normally. Of course, I had to make sure about that while the item is still newly acquired, in case I need to return it.I really like the scope and I did in fact already download both manuals. I bought some cheap 100MHz probes. They are a bit stiff but seem to work fine.Is there a way to hack generic probes so that they act like Tektronix probes, with that little 10x sensing peg on the BNC connector?Perhaps the only thing that I wish was better about this model is the fact that the measurements section does not have RMS. I didn't realize that until I got the unit.And the part that I don't quite understand, yet, is the A and B mode capability. I have not been able to understand, yet, what that's for.But like I said I am very happy with the scope and I also like that seller's handling of the sale (the communication and the truly expert packaging).At this time I do not have a function generator but I can still rig up some tests signals to post images.Thanks...

author: Johnny10
author_rank: Frequent Contributor
timestamp: May 22, 2020, 02:06:58 pm
content: Might also help to take focused pics if you want us to give complete answers.Difficult to see if brightness is turned too high.

author: Electro Fan
author_rank: Super Contributor
timestamp: May 22, 2020, 04:08:30 pm
content: As Johnny10 said posting better photos will help folks give better info and advice.On the A and B question, here is a video that might help:https://youtu.be/54roz8IUoVIThe video shows the controls on a 24xx model which work somewhat different than the controls on the 22xx models but the scope functionality is similar, just not using the same controls in the exact same way - the concepts are pretty similar.https://download.tek.com/manual/070608300web.pdfHere is another on the 400 models:https://youtu.be/0enuruGWYk8The 400 model controls are different (they were predecessors to the 22xx and 24xx scopes, of course) but again similar functions in terms of the intended capability.Basically, Tektronix provided ways to show two views (A and B) of the same signal, each with their own time base setting. This allows you to see more detail in a selected part of the signal and let’s you navigate, measure, and even trigger based on the second view (in addition to the first view). The trace separation control can be useful in addition to the vertical control. Overall “A and B” (often referred to as a delayed time base function) is similar to the zoom function on a digital oscilloscope.w2aew has made a bunch of great videos in case you haven’t already discovered them - tons of tremendous Tektronix and overall test equipment and electronics videos - highly educational.

author: rstofer
author_rank: Super Contributor
timestamp: May 22, 2020, 06:01:59 pm
content: You just got the deal of a lifetime on a scope! Even if you decide to get a DSO later on, you will still want to keep the CRO. I have a Tek 485 that I have had for quite a while ($200 used on eBay) and it still stands up under my bench for the time when I need the extra bandwidth or I'm just feeling nostalgic.If you want probes that support the Tek ring features, I suspect you are going to have to buy Tek probes. Finding the right probe will be a challenge.My 485 has the feature, I don't bother with it.

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 06:21:45 pm
content: Quote from: rstofer on May 22, 2020, 06:01:59 pmProbemaster also makes scope probes with the readout actuator pin. It adds about $10 to the cost of a fixed 10X probe; more to a switchable one. (I don't have any of their probes, but they seem to be well regarded from what I've seen.)https://probemaster.com/4900-oscilloscope-probe-basic-kit-150-300-mhz/-Pat

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 06:31:19 pm
content: Thank you all again for your informative replies.I already watched many videos by w2aew (some even more than once). I'll definitely be watching more of them as I learn.Thank you also for the basic A/B mode explanation. Now at least I know what it's all about. The manual doesn't really explain it clearly. I'll study those resources tonight.Those ProbeMaster probes look nice. Perhaps down the line I'll upgrade to that. Thanks for the info.The photo I initially posted was a still grab from a video. I had to make a video recording to grab a still of the exact time I wanted to show.Here are some photos of the scope in XY mode. I breadboarded a transistor curve tracer circuit so I could test the XY mode. What is odd, as you can see on the photos, is that I get a diagonal line coming from CH 1, when the CH1 button is pressed. My 20MHz scope doesn't do that.I'm sure the Tek scope is not malfunctioning but I can't understand why it does that when I press the CH1 button. Any ideas?Thanks...

author: engrguy42
author_rank: Frequent Contributor
timestamp: May 22, 2020, 06:38:31 pm
content: Quote from: rstofer on May 22, 2020, 06:01:59 pmBut...it's, like 30+ years old...And, y'know, there's this "bathtub curve" thing. And, it's from eBay. I mean, did someone spill Coke on it 16 years ago? Did they cross their leads while measuring high voltage 22 years ago? Did they open it up and change components 7 years ago?I dunno, I can't see why someone would buy something like this. Seems like a huge risk. And nobody can look back and say "Hey, I've had mine for 43 years and it works fine, no sweat". Because it hasn't been around that long.Good luck.

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 07:00:32 pm
content: Quote from: engrguy42 on May 22, 2020, 06:38:31 pmWhat is a bathtub curve?I like buying old stuff and I know there's a risk. But even if you buy a new scope you don't know if anything got rattled when the UPS handlers dropped the box from the conveyor belt, from 3 feet high. We also don't know if there are any cold solder joints in a new one, that will crack after a few months due to thermal expansion.I am actually planning to open it up and look at the components and at the solder joints.Thanks...

author: wizard69
author_rank: Super Contributor
timestamp: May 22, 2020, 07:09:24 pm
content: Quote from: engrguy42 on May 22, 2020, 06:38:31 pmSo? In less than half a year I will be 60 and I still believe I'm useful!!!These old analog scopes do have a few advantages and frankly it is good to have one around. I liken this to work where we have several instruments that get used occasionally. A long as they work there is no real reason to replace them. Does better tech exist, almost certainly. Is it needed to do the job - nope.The same argument often comes up when talking about analog VOM's on the bench. Yeah a digital is better in 99% of the cases. However if you want to demo decay of a charge in the classroom an analog meter makes it far more obvious what is going on.QuoteIn a way you kinda have to expect that instruments of this age have had work done on them. It is sort of like buying a used car, at some point they all go into the shop.QuoteAnd yet I've had tools that I've literally have had since my teen years. I probably would of had instruments from that era but I couldn't afford them so no instruments 40 some years old. If somebody can save a few bucks buying used and gets started with good instrumentation early I'd say go for it. Buying used is a gamble no doubt there, but that is the case even if you are buying a home. Buy used you take on the responsibility for maintaining the device, it can be a good trade off if you have good tech skills.To look at this another way when do you give up on old tech. Back in 1984 I walk into a new job in a factory that I imagined was fairly modern. Some of the machinery in that plant was relay based or running on old 5TI PLC's with 256 bytes of RAM if I remember correctly. Ended up maintaining those old 5TI's for a long time! In tech school I literally had one teach suggest that I didn't need to worry about tubes when asking about them. Yet that first job introduced me to an RF amplifier that needed a forklift to move ( I was most happy when it was replaced). just because something is old doesn't mean there isn't value in it. Frankly a quality built bit of instrumentation can have a very long life compared to some of the more harshly used industrial electronics.

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 07:09:47 pm
content: Quote from: Adinol on May 22, 2020, 07:00:32 pmA bathtub curve is the normal failure pattern for well designed electronics and mechanical systems. It refers to the plot of the failure rate over time, which looks like the cross section of a bathtub. When the things are new, there may be a relatively high 'infant' failure rate, where marginal components with manufacturing defects will fail right out of the gate. Once these early failures have occurred, the rate of failure drops to something very low for a long time. Eventually, things start simply wearing out from old age and use, and the failure rate rises again at end-of-life of the instrument or machine.I wouldn't worry about it WRT to your new scope - ignore the troll. He likes to stir things up.-Pat

author: wizard69
author_rank: Super Contributor
timestamp: May 22, 2020, 07:15:52 pm
content: Used instruments can be good buys. Often they become available after going off lease or a project shuts down, these can be kinda expensive but still a bargain. Older equipment suffers will certainly have had a different life experience but that is where careful shopping comes in. For many of use it comes down to either having a hobby or not, quality bench instruments cost a lot, so carefully considering them for the bench should be part of the plot.That came out of nowhere.Quote from: Adinol on May 22, 2020, 07:00:32 pm

author: wizard69
author_rank: Super Contributor
timestamp: May 22, 2020, 07:24:49 pm
content: Quote from: Cubdriver on May 22, 2020, 07:09:47 pmFor electronic instruments that belly in the curve can be extremely wide compared to say high power RF equipment. This especially when it comes to the higher quality manufactures. In some cases stability and drift can even get better with age.People seem to like to knock old analog scopes and frankly I'm not sure why. A new digital scope can certainly be a good investment, especially if one is heavy into digital electronics. However analog scopes are fine for many and are at price points that are hard to dismiss. Even if you had to buy three to get one working you likely have saved money over a digital scope.

author: engrguy42
author_rank: Frequent Contributor
timestamp: May 22, 2020, 07:27:16 pm
content: Interesting how someone can clearly define a well known engineering description of the likelihood of failure (which is a standard consideration by real companies in the real world), and in the next sentence wave their hands and tell someone to ignore it, and then follow that with a personal attack.As usual in this forum, no facts explaining WHY it's reasonable to ignore the bathtub curve in a 30+ year old device (which anyone on the planet would consider FAR beyond its service life and at high risk of failure).

author: Gyro
author_rank: Super Contributor
timestamp: May 22, 2020, 07:36:34 pm
content: Quote from: engrguy42 on May 22, 2020, 07:27:16 pmOh, will somebodypleasegive him some scientific measurements of the bath!

author: engrguy42
author_rank: Frequent Contributor
timestamp: May 22, 2020, 07:46:48 pm
content: Let's be honest. People here like these things for nostalgia reasons. No facts involved. And they can't accept anyone who questions that.Fine. Just try not to recommend that others buy these things solely because YOU like them.

author: Electro Fan
author_rank: Super Contributor
timestamp: May 22, 2020, 07:56:01 pm
content: Ok, you are at the beginning of a fun and great journey. Nice curve tracer.Regarding the diagonal line, my guess is that it is related to X-Y. Take a look at post 36 in this thread:https://www.electro-tech-online.com/threads/x-y-scope-mode-diagonal-line.139864/page-2Try playing with the buttons over to the right under Mode and Source; there are lots of combinationsAs for the probes, I have a couple/three-ish Tek scopes and early on I bought some Probemaster probes. They were/are very good in terms of both price and performance, no doubt. They have the feature that let's the probe sense the 1x/10x ring. No reason not to try Probemaster but I've also found over the years that there are still good Tek probes available on eBay - some vintage but gently used/well cared for, and occasionally some that look like they came from the factory with little or no use. You can't be 100% sure what you will be getting (until you get it) but if you go slow and take the time to read lots of eBay ads and study the photos and do some Q&A with the sellers you can improve the good to surprise ratio, and you will likely be able to find some good Tek probes. If you are still more selective and only go for purchases that will allow returns you are probably doing all you can do. At some point everything that has potential reward probably has some risk but the risk can be mitigated with good study.This site (along with others and Tek manuals) will help you piece together what probe models to look for.http://www.barrytech.com/tektronix/probes/tekprobes.htmlEnjoy the 2246.---Edit: Mode and Source might not be part of the matter. It's been awhile since I used XY. Here is a good explanation:https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=2838609&nid=-32110.1203274.02&id=2838609I could be wrong (often am) but I think what it's saying is that with XY the scope is effectively using the inputs of both channels to make the trace - even when one channel is set to Off. When you turn both channels on the scope is making two XY traces. You can see this by making ovals or circles with two inputs (2 channels) from a function generator. With two channels from the function gen connected to the scope inputs for channel 1 and channel 2 but just one scope channel set to on you will get one oval or circular trace; with both scope channels set to on you will get two oval or circular traces.Another excellent w2aew video (on Lissajous patterns and XY):

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 22, 2020, 08:25:05 pm
content: Quote from: engrguy42 on May 22, 2020, 07:46:48 pmJust as a point of clarification, I specifically wanted an analog scope and it was not something that anyone here recommended to me. I did watch Dave's YouTube video about buying an analog scope, but his recommendations did not influence me in any way. I already knew what I wanted.Also, back in the day things were designed to last a lifetime (or several generations). Nowadays, companies deliberately design things that will break and be outdated. That's how they make more money.One day I will probably get a digital scope, but I am waiting for a next generation of those scopes but since they are so expensive I don't intend to pay for one. I already have a plan how I am going to steal one straight from the factory. Hey, I'm just kidding...Back on topic, now...Quote from: Electro Fan on May 22, 2020, 07:56:01 pmTotally. One thing I have to figure out how to do is to flip that X axis. I guess the output of the X has to go through an OP Amp circuit. But that's for another thread...Quote from: Electro Fan on May 22, 2020, 07:56:01 pmThanks for this info. I already played with the other settings but could not see that it made any difference. I'll have to do some more playing.Quote from: Electro Fan on May 22, 2020, 07:56:01 pmThank you for this...

author: AVGresponding
author_rank: Super Contributor
timestamp: May 22, 2020, 09:03:59 pm
content: Quote from: engrguy42 on May 22, 2020, 07:46:48 pmI agree with you, up to a point, but you should also remember to heed your own advice...If facts are your grail, consider this; the repair of a 2465 (no I don't own one) with its huge base of knowledgeablefansowners, vs the repair of a modern digital scope (fill your own make/model details in) with a much smaller knowledge base.Add to this the increased difficulty of dealing with near microscopic smd components on modern boards, which necessitate even more specialist gear to work on, and the improved knowledge of the manufacturers on the MTBF bell curve of their components, which results in lower engineering margins and frequently much lower useful service life.FYI the bell curve (inverted bell curve in the context, if you want to be pedantic, and I usually am, so I can't criticise others) relates to the observed failure rate ofmanufacturedscopes, in this context.The ones still operating, whether through being on the favoured side, or having being repaired and therefore not strictly belonging in that curve, actually have a lower than (statistically) normal failure rate.Incidentally, due to the aforementioned improvements in predicting MTBF rates, I expect the inverted bell curve for modern scopes to bemuchnarrower.Time will tell, ofc.Ultimately, buy what you like, enjoy using it, and give the one/two (depending on your national heritage) fingered salute to those who try to spoil your pleasure.

author: tautech
author_rank: Super Contributor
timestamp: May 22, 2020, 09:36:11 pm
content: Quote from: Adinol on May 22, 2020, 08:25:05 pmBack when I got my first scope.....any working scope was better than none.QuoteI take issues with this as this has not been my experience, rather exactly the opposite.Test equipment is not designed to be some throw away consumer item and in 7 years I've been selling new equipment HW failures are very very rare.QuoteIt's sad a good DSO is outside your budget as they are more capable than any CRO and ~double what you paid for your TEK (BTW good old CRO) you can have something much more capable.Don't close your eyes to what lies ahead for you in the future as you gain experience with a CRO and discover what you can't do with them that a DSO can do without breaking a sweat.Enjoy your 2246 while you have it.

author: Electro Fan
author_rank: Super Contributor
timestamp: May 22, 2020, 09:41:48 pm
content: Quote from: Adinol on May 22, 2020, 08:25:05 pmJust to clarify, after writing that I decided it might be incorrect so I added an edit; hopefully the edit part is more on the mark.https://www.eevblog.com/forum/beginners/did-i-buy-a-decent-oscilloscope/msg3078423/#msg3078423

author: engrguy42
author_rank: Frequent Contributor
timestamp: May 22, 2020, 10:15:16 pm
content: AVGresponding, I hear ya, up until you talk about giving the bird to those who try to "spoil your pleasure".Why? Why do you guys take equipment personally? Why do you give a flying F*** what anyone says about a freakin' scope? Or meter? Or whatever? Is it an ego thing, where it becomes YOUR equipment and anyone who talks against you think is talking against YOU?Geez guys, get a grip. Accept and admit that maybe those scopes AREN'T the greatest thing in the world, and maybe they DO have some serious drawbacks for a lot of people. Hell, I have fond memories of those old scopes, and was even thinking of buying one. Until I started thinking about what a pain they'd be (no USB, no storage, etc.). There's a lot that sucks about them, and there's a lot good about them, just like there are pros and cons to every freakin' piece of equipment I own. Nothing's perfect. Deal with it.

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 10:37:43 pm
content: Quote from: engrguy42 on May 22, 2020, 07:27:16 pmRight. As opposed to you, who came into a relative newbie's thread on buying an oscilloscope to throw cold water on him and sow fear, uncertainty and doubt in his mind regarding his purchase.How about YOU cite some facts regarding the failure rate of the Tek 2246, which is the scope in question, and provide some specific concerns? Where is this model on the bathtub curve? Got any facts or data points, or is it just conjecture on your part? Instead you throw out vague nonsense like "It's 30+ years old!" "You bought it from Ebay" "Someone might have spilled Coke on it" (not sure how that one relates to a bathtub curve, but whatever...)-Pat

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 10:48:44 pm
content: Quote from: engrguy42 on May 22, 2020, 07:46:48 pmLike suggesting ATX power supplies in a thread where a guy asked about a variable bench power supply and gave an actual model number?!? <waves> Hi, Pot!!And as for facts, I can go on thefactthat I have many of these older instruments, and they're working just fine, thank-you-very-please. Perhaps you should consider that people like these things because they were state of the art high end lab grade gear in their heyday, and while new equipment may be smaller or lighter or prettier, that doesn't change the fact that these instruments still work. Maybe you should look beyond your disdain for them and perhaps realize that others may have different motivations than those you ascribe to them. Take a sliver of your own advice, and don't take issue with suggestions given by others regarding older instruments becauseyoudon't like them.-Pat

author: engrguy42
author_rank: Frequent Contributor
timestamp: May 22, 2020, 11:09:26 pm
content: I don't "like" ATX power supplies. Or any power supply for that matter. I don't "dislike" old analog scopes. Or any other scopes. I don't care about them. I only care about their capabilities. ATX power supplies have a lot of capabilities and benefits that some people refuse to accept. And they have a lot of disadvantages too. Same with analog scopes. Or any other tool.If I suggest someone consider a tool, I don't give a flying F*** what they choose. I do it based on capabilities, not emotional ties.Apparently it's difficult for some to comprehend that others aren't in the game of liking or disliking equipment and tools.Like I said, I grew up with analog scopes. But like any other tool, I never got an emotional attachment. I learned that what's important is their pros and cons. And if someone tells me my scope/meter/whatever is crap, I'll probably say "Yeah, it does have some downsides". Because I don't freakin' care about equipment.I just know that I'd never recommend to anyone to buy a 30 year old car. Or a 30 year old computer. Or a 30 year old anything. Unless they knew what they were getting into and were willing to put up with the crap.

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 22, 2020, 11:28:08 pm
content: OP: I think the diagonal line is due to having two vertical channels enabled. Turn off the one you’re not using and it should disappear. There is no RMS measurement since it’s not analyzing waveforms.QuoteThat will be a disappointment unless you’re really willing to tear into it. Really not much to see with just the cover off. You’ll need a Torx 15 to get anywhere, add an extension if you want to get the fan out to clean things.The fan is inside the power supply box and to get to that, you’ve got to pop off the digital display generator board that is on the top of the unit. There is a 3 volt tabbed CR123 type backup battery on the board so don’t set it on anything conductive if you pull it.You have to use a small, 1/8” diameter screwdriver to remove the four ribbon cables from the display board then pull the board and remove the screws holding the power supply cover in place. Tons of Torx 15’s everywhere. Once inside, you can pull the fan using an extension from the crt side and either replace it if the bearings are noisy or just clean it if that’s all it needs.You can measure the power supply ripple from the vertical/sweep board on the bottom of the unit. The allowable ripple voltages are listed in the service manual.If you do pull the power supply out of the unit, watch out for the 160v supply, the caps will develop charge out of the unit as there is no bleeder resistor, it will bite you if you’re not careful.

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 23, 2020, 12:59:58 am
content: Quote from: WattsThat on May 22, 2020, 11:28:08 pmThis is the part I don't understand. In XY mode CH1 becomes X and CH2 becomes Y. So doesn't that mean that both channels are used, except that they are used in XY mode?The part that I find odd is if I have CH2 selected I get the proper image from the curve tracer. But if I have only CH1 selected I get only the diagonal line (even if the CH1 BNC is connected to the probe that is probing the X output of the curve tracer).Since I have no experience with this I don't know if this is a design issue of this model or if something is wrong.I re-read that part of the manual many times. It says."X-Y - The signal applied to CH1 or X input connector produces the horizontal (X-axis) deflection. Signals applied to any vertical input connector and/or ADD may be selected to supply the vertical (Y-axis).The X-Y displays are horizontally positioned by the Horizontal POSITION control and vertically positioned by the associated vertical channel POSITION control."That's all it says and it doesn't mention which buttons of the channel selectors should or should not be pressed.Quote from: WattsThat on May 22, 2020, 11:28:08 pmOh, I see, thanks for the clarification.Quote from: WattsThat on May 22, 2020, 11:28:08 pmI really just want to make sure there are not damages caused by resoldering components and that there are not bulging electrolytic caps, burnt components and that sort of thing.Speaking off, is it common practice to change old electrolytic caps in old scopes?Thanks...

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 01:10:51 am
content: Quote from: engrguy42 on May 22, 2020, 06:38:31 pmSo what? It could fail some day? What's your point exactly? Why do you have to come in here and piss on somebody's parade? We're not talking a huge investment here, and it doesn't sound like the OP is planning on trying to rely on their scope to make a living. Maybe it will crap out in a week, big deal, stuff happens. It may also run for another 30 years without any issues at all. As with most things in life, nothing is guaranteed, sometimes you win, sometimes you lose, but I've always gambled and bought old gear and I've won FAR more times than I've lost. I've got a Tek 465B that I bought used 20 years ago when it was 20 years old already and it has never given me any trouble at all. I very rarely use it anymore since getting a DSO however the XY mode on the 465B blows away every DSO I've ever tried for that so that's the scope I get out when I want to work on a vector arcade board. I also got a solid 10 years of productive service from it back when DSOs were well out of my budget, it allowed me to develop and debug countless things that would have been virtually impossible to do without a scope.If this were a $50k purchase then I'd agree that it's a "huge risk" but a few hundred bucks? That's a very small wager as far as I'm concerned, I've seen guys blow more than that in a night at the bar and have nothing to show for it the next day besides a hangover. The OP will have a cool old scope that was a high end very expensive instrument in its day and it's still as capable and useful as it ever was. I have little doubt that he will get his money's worth of enjoyment and education out of it. As with many things, it's less about what tools you have and more about what you manage to do with them.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 01:19:02 am
content: Quote from: Adinol on May 23, 2020, 12:59:58 amThat depends, and it's not specific to scopes.Surface mount electrolytic capacitors are absolutely notorious for failing, and they fail in such a way that they leak corrosive electrolyte out which wreaks havoc and causes all kinds of damage. Because of that, I always replace all of those in old gear.More conventional through-hole capacitors I'm not so quick to just change them out just because they're old. The exception here is output filters on switchmode power supplies, that is a brutal environment that is very hard on capacitors and failure is common. I also look closely for leakage because they can and do occasionally leak although not nearly as often as the surface mount type. Otherwise my general opinion is along the lines of "if it ain't broke, don't fix it". I've seen people screw up equipment that was working by doing a ham-fisted bulk re-cap, and I've seen people replace older but very good quality capacitors with the cheapest off-brand Chinese junk they could find that crap out a year later.Anyway, I suspect you just want to have an excuse to pop the hood and take a peek inside, go for it, I'd do the same thing myself. Have a look, vacuum out the cobwebs, blow the dust out of the fan, marvel at the engineering and attention to detail, a lot of those old Tek scopes are works of art.

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 23, 2020, 01:24:57 am
content: Re-capping: You’ll might get as many opinions as you get responses on that one but I second what James said. I don’t do it as a matter of habit, if caps are leaking, bulging or there is excessive ripple, of course they get replaced. But just replacing them because they are X years old, no, I don’t do that. Measure the ripple, if it’s good, the caps are good. I don’t “fix” that which is not broken. Maybe I’m just lucky or maybe I just don’t have that much really old gear.You cannot get to the solder side of the vertical/deflection board without major and I do mean major disassembly. Everything is wave soldered and through hole, not much to see or do unless it’s broken.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 01:40:24 am
content: Quote from: WattsThat on May 23, 2020, 01:24:57 amI have multiple old scopes, multiple other bits of test gear, several 80s TVs, numerous radios, a dozen 70s-early 80s arcade cabinets, various audio gear and other stuff, dozens of devices in total with many original electrolytic capacitors, even some as old as late 60s. I've replaced some of the capacitors in many of these things but far from all and some of the old gear is un-touched and still working.Old age is not a disease, and stuff doesn't automatically stop working just because it's old. It has worked out well for me that there are so many people who assume old stuff is no good because I've gotten a lot of nice cast off stuff. I once bought car for $500 because the guy thought the engine was shot because it had some water in the oil. I drove it as a daily driver for 17 years and would probably still be driving it if I hadn't been rear-ended by a semi. I owned it longer than the original owner, and I was still driving it when they replaced the car they bought to replace the one they sold me. If you take care of stuff it can last a very long time and old gear often has the advantage that you can actually get a schematic and service info for it.

author: Cubdriver
author_rank: Unknown
timestamp: May 23, 2020, 02:15:12 am
content: I'll third james_s re the caps. I generally don't shotgun, either, unless they're known to be bad (such as waxed paper caps that have been in a damp environment - pretty much guaranteed to have become high value resistors.) A few old counters and meters have needed electrolytics, but others of similar vintage have not. Companies like HP and Tek used quality parts for these things; unlike Madman Muntz they weren't trying to squeeze out every possible cent in the BOM.TL;DR I suggest replacing caps on an as-needed basis.-Pat

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 23, 2020, 02:25:06 am
content: What you guys say about the caps makes sense.I will open up the unit in a few days but I won't go crazy. I also have a black light, so I'll use it to see if any old residue from possible leakage shows up.I was just doing more experimenting with the X-Y mode and it turns out that if you activate any other channel that is not connected to Y with the probe, it will add a line on the display. But only CH1, which is X, adds a diagonal line. If you activate CH3 or CH4 they add a horizontal line. Same happens if you connect the probe to CH3 and then you turn on CH2 it will add a horizontal line.It does seem that it part of the design, but I can't make much sense why they designed it like that. Unless this kind of design actually adds a useful feature that I have not discovered yet.One of my reasons for an analog scope was in fact so I can use a curve tracer to match transistors. I want to work on audio amp circuits.Thanks...

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 23, 2020, 03:09:28 am
content: Quote from: Electro Fan on May 22, 2020, 04:08:30 pmNow I had some time to watch those videos. They were really helpful and now I understand how to use this feature.Thanks for those links...

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 03:23:25 am
content: You'll also want to read the manual. XY mode when properly configured should be very straightforward. A voltage on one channel will move the dot horizontally, a voltage on another channel will move it vertically. If you're getting diagonal lines or multiple lines when only using one input at a time then something is wrong with the setup.

author: PixieDust
author_rank: Frequent Contributor
timestamp: May 23, 2020, 03:28:00 am
content: You can get some probes that have the x10 pin sticking out that are not Tektronix if you look around. I got mine from Caltest Electronics but I'm sure there are others.For example this one doesn't have the pin:https://www.caltestelectronics.com/ctitem/20-probe-oscilloscope-passive-voltage/CT2674AThis one appears to have the pin:https://www.caltestelectronics.com/ctitem/20-probe-oscilloscope-passive-voltage/CT2676ARAWrite them an e-mail to make sure before buying.As for capacitors, I had some RIFA capacitors in mine that blew up about 5-10 mins into me turning the unit on. I obviously had to replace mine:https://www.eevblog.com/forum/testgear/blew-up-my-first-oscilloscope!!!/25/

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 25, 2020, 04:33:24 pm
content: Quote from: james_s on May 23, 2020, 03:23:25 amYes, of course, I did start reading the manual even before the scope arrived. Sometimes things aren't too clear in these manuals, though, as they assume the readers have a certain level of knowledge in the field.I've tested the scope in various scenarios and I am liking it.There is only one additional thing that I noticed, that I need to ask about.When the input signal is below 200mV pp the automatic voltmeter readings put the cursors noticeably away from the peaks. Please see the images.This is the case even if the scope has been warming up for a few hours and even after self calibration.I think that's probably normal for such weak signals, but I thought I'd ask.Thanks...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 25, 2020, 05:33:31 pm
content: The bathtub curve, like MTBF, applies to populations, not individuals. At best it is a guideline for individuals.Your scope could have been owned by a little old lady who kept it in an air-conditioned lab and only used it on Sundays to measure DC.

author: Frankentronics
author_rank: Regular Contributor
timestamp: May 26, 2020, 04:11:28 am
content: I just came up with a method of doing a very accurate compensation of the 10x probes.Perhaps I am reinventing the wheel, but I thought I'd share my idea, just in case.So, you hook up CH1 and CH2 probes to the test terminal and first do as accurate compensation as you normally would. Then you invert CH2, press the ADD button and turn off CH1 and CH2. Now you see a line that's almost a flat line, but you can see the tiny jumps between CH1 and CH2. So, now you just do your final compensation to get an absolutely flat line.That's it.

author: maginnovision
author_rank: Super Contributor
timestamp: May 26, 2020, 05:23:51 am
content: You're supposed to be compensating the probe for the inputs, not to each other. You're taking the error difference in two channels and trying to zero it, that's not compensating anything useful as far as I know.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 26, 2020, 11:23:31 am
content: Sounds like you bought a fine working scope.Price is fine too. And you learned how to use it!If it breaks, there are lots of folks who can help you fix it.I have owned scopes made from the 1950's on up to a DSO.My only criticism of your scope is that like all older tek scopes, there are too many buttons, these are necessary for all the functions though.The scopes I really do not like are the early DSO things with the video monitor (not a CRT) tube. I just do not like the way the display looks and of course they are slow.Curve tracer is cool, I have one.I currently use a HP 1980 scope system that is an analog scope with digital functions, I like it but do not buy this one, it is a real goofy thing to fix.WallyOh, and by the way, i think that diagonal line is the returning trace in xy mode, I think that is normal.Groups.io has a TekScopes group that can be helpful.