Did I buy a decent oscilloscope?

[Frankentronics]

....Just try not to recommend that others buy these things solely because YOU like them.

Just 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 Nowadays, companies deliberately design things that will break and be outdated.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...

Ok, you are at the beginning of a fun and great journey.  Nice curve tracer.

Totally. 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...

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-2
Try playing with the buttons over to the right under Mode and Source; there are lots of combinations

Thanks 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.

As 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.html

Enjoy the 2246.

Thank you for this...

[AVGresponding]

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.

I 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 knowledgeable fans owners, 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 of manufactured scopes, 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 be much narrower.
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.

[tautech]

I specifically wanted an analog scope and it was not something that anyone here recommended to me.

Back when I got my first scope.....any working scope was better than none.

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.

I 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.

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.

It'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. 

[Electro Fan]

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-2
Try playing with the buttons over to the right under Mode and Source; there are lots of combinations

Thanks 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.

Just 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

[engrguy42]

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.   

[Cubdriver]

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).

Right.  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

[Cubdriver]

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.

   Like 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 the fact that 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 because you don't like them.

-Pat

[engrguy42]

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.   

[WattsThat]

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.

I am actually planning to open it up and look at the components and at the solder joints.

That 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.

[Frankentronics]

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.

This 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.

There is no RMS measurement since it’s not analyzing waveforms.

Oh, I see, thanks for the clarification.

I am actually planning to open it up and look at the components and at the solder joints.

That will be a disappointment unless you’re really willing to tear into it....

I 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...

[james_s]

But...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.

So 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. 

[james_s]

Speaking off, is it common practice to change old electrolytic caps in old scopes?

That 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.

[WattsThat]

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.

[james_s]

Maybe I’m just lucky or maybe I just don’t have that much really old gear.

I 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.

[Cubdriver]

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

[Frankentronics]

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...

[Frankentronics]

On the A and B question, here is a video that might help:

https://youtu.be/54roz8IUoVI

...Here is another on the 400 models:

https://youtu.be/0enuruGWYk8

Now 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...

[james_s]

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.

[PixieDust]

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/CT2674A

This one appears to have the pin:
https://www.caltestelectronics.com/ctitem/20-probe-oscilloscope-passive-voltage/CT2676ARA

Write 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/

[Frankentronics]

You'll also want to read the manual...

Yes, 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...

[Alex Eisenhut]

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.

[Frankentronics]

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.

[maginnovision]

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.

[Wallace Gasiewicz]

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.
Wally

Oh, 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.