Oscilloscope question for the hardcores

On3s&Z3r0s

So, with all the DIY'ers on the boards, I'd imagine some of you have some experience with oscopes. I'm looking at buying one used, and was wondering if there are any quick tests one can do to determine if a scope is generally in good working order? There are a few available on CL right now... a B&K 20Mhz and a Tektronix 2235 100mhz. It sounds like the Tek would be a good deal if it's ship-shape, but I'm new enough to these that I wouldn't know if there is any easy way to get a good idea of that. Any suggestions or are they just too complicated a piece of equipment to check out easily?

Outfitter03

If you have a signal generator and a voltmeter you can check out most functions quite quickly. If you have never run an O scope it would be helpful to have a knowledgeable friend help with the initial checkout.

Basic functions with a single input are not that hard to do, but trying to check for functionality and at the same time learn on your own, will take a little bit of time.

Can you give a little more information on your experience level. There are some basic instruction manuals you can find online if you are completely new to using this piece of test equipment.

On3s&Z3r0s

I've used them before in an electronics course I took years ago... it was a Tek but I don't even know which model... unfortunately I don't have a very portable signal generator right now. The Tek 2235 is being sold without leads... not very promising so I'd have to pick up an aftermarket probe in order to test it anyway. I do have someone I could ask who has more electronics experience and might even have a generator. That failing, I guess maybe I'll just buy the B&K and hope for the best. It's only $75 so worst case I make a mistake that costs less than a hundred anyway.

megasat16

If you are only repairing / testing the audio equipments, 20MHz B&K is OK.

The Tek would be nicer to have but the B&K would works for you too. The important thing is whether any of them works or not. The probes are usually expensive at around $30 or more for even a used but good one.

jinjuku

Check out some of the computer based scopes also. Any where from $150 to several $K.

Zaigrith

Check to see if there is a square wave test point on the front. It should be 1khz but check the manual to see for sure. If its there, measure and confirm the signal to verify your scope is working.

disneyjoe7

Zaigrith wrote: »

Check to see if there is a square wave test point on the front. It should be 1khz but check the manual to see for sure. If its there, measure and confirm the signal to verify your scope is working.

Yes a scope should have a test point jack / hook in front to calibrate it. If I recall 1khz and 1vpp.

On3s&Z3r0s

Thanks for the tips... I'll definitely see if I can find the manuals online and figure out where the test point is and basic testing procedure. Then I just have to get the probe thing figured out. I assume they're pretty universal... just a BNC connection it looks like.

Zaigrith

The probes are generally universal, there are 1x 10x 100x (attenuation) and varying capacitances but for the most part you should not have to worry about any of this unless you are doing precision measurements. Attenuation is nice when measuring voltages larger than the specs of the scope, so keep that in mind.

ViperZ

2235 is a great scope. 100Mhz is probably an overkill for what you want, but who cares - it will do what you want. I used old analog B&K (sold after a month) and old HP (sold after 3 months) and hated them. Tektronix is much easier to learn (at least to me) and much easier to work with.

On3s&Z3r0s

Thanks for the feedback on the Tek... I'm debating whether to go with a used Tek (there's a 2245 I think I could score for under $300 with probes, recently calibrated by someone who sounds like he knows what he's doing) versus a new Rigol DS1052E. The Rigol has a lot of positive reviews on Amazon for being easy to use and brand new at around $400 with warranty. Seems like maybe the Rigol would be the safer bet for a newbie (assuming I can figure out the engrish manual ).

Zaigrith

I have the rigol, you can mod it to 100mhz over a serial cable. http://www.youtube.com/watch?v=LnhXfVYWYXE

megasat16

Digital Storage Oscilloscope (DSO) and Analog Oscilloscope such as Tek 2235/2245 are two different animals.

Oscilloscopes are chosen based on the applications. For audio with precision measurements, the analog would be an ideal choice where you have to measure the noise level and amplitudes very accurately.

DSO usually has an error of margin based on the digitizing frequency. The higher sampling rate, the better it is close to an old analog scope. But the cheap DSO with lower sampling rate could have inaccuracies or digitizing errors.

Having said that, digital scopes have many features, functions and ease of use that the older Tek 2245 or 2235 lacks.

In General, a properly calibrated analog scope such as Tek 2235 / 2245 will have more accurate waveform representation than a cheap low sampling rate digital scope.

But unless you require surgical precision for what you want to do, none of these matter. You can forget analog scope and consider a new Rigol over a used Tek 2245 coz Rigol price is very reasonable and come with warranty.

On3s&Z3r0s

I don't think I need surgical precision. I doubt I'd ever use the 4 channels in the 2245, but I guess it doesn't hurt to have them if the price is right. I just would like to use it for things like calibrating tuners and verifying the output of op amps when I swap them out in a DAC. Probably all of these options are overkill for the use I'll get out of it, but I don't know anyone who owns one and it doesn't seem like there's any alternative piece of test equipment that will get the job done.

megasat16

I don't know about the price of 2245 nowadays but properly calibrated 2245 with good probes may well worth $300.

But from what you said, you probably don't need a scope. There are many DIYers who don't own an oscilloscope to swap out op-amps or align tuners. But a scope is a very nice thing to have if you don't mind a few bills.

There is no alternate equipment to a scope. An oscilloscope to an Enginner / Technican is akin to a stethoscope for a doctor or a hammer for a handyman.

ViperZ

You may want to consider a USB-based scope. I've seen those on ebay for $200-300. Hook it up to your laptop/PC and voila - colour interface, storage capability, etc etc.
Personally, I have a 350 MHz scope from Tek (2465A if I remember), it even has a multimeter option sitting on top. Love that machine. Of course, I use it like once a month at most lol.

mhardy6647

Solid state Tektronix or H-P would be hard to beat and at this late date the price should be right. Establishing the linearity and accuracy of the amplifiers might be difficult without calibrated frequency and voltage sources. Just eyeballing a sine or square wave from a decent function generator ought to give a pretty good impression of the Y-axis amp linearity. I think making a Lissajous figure with two sine waves of the same frequency (but 90 degrees out of phase) would be a pretty good test - should get a nice round circle :-) http://www.jmargolin.com/mtest/LJfigs.htm

You really don't need much amplifier bandwidth for audio. Good old analog color TV even only required a 5 MHz scope, and the waveforms for NTSC color video are pretty complex.

This is a nice primer on oscilloscope use:
www.tek.com/Measurement/App_Notes/XYZs/03W_8605_2.pdf

Here are a couple of other, albeit more vintage, resources on knowing your 'scope, courtesy of Pete Millett:
http://www.tubebooks.org/Books/smith_oscilloscope.pdf
http://www.tubebooks.org/Books/haas_oscope.pdf
http://www.tubebooks.org/Books/Middleton_troubleshooting.pdf


I'm probably not the best person to ask about oscilloscopes, though :-P

On3s&Z3r0s

^^^ Damn, that thing is a relic! By which I mean sacred and beautiful... very cool. I like how the label on the cart says TYPE 202 SCOPE - MOBILE. Mobile as in a Mack truck is mobile.

Anyway, enough of that went over my head that I feel like I did the right thing by letting the 2245 go. I think I should read up and wait until I can justify the purchase. And then I'll figure out whether to go analog or digital.

Here's something fun for fans of scope art...

mhardy6647

On3s&Z3r0s wrote: »

^^^ Damn, that thing is a relic! By which I mean sacred and beautiful... very cool. I like how the label on the cart says TYPE 202 SCOPE - MOBILE. Mobile as in a Mack truck is mobile.

Anyway, enough of that went over my head that I feel like I did the right thing by letting the 2245 go. I think I should read up and wait until I can justify the purchase. And then I'll figure out whether to go analog or digital.

Here's something fun for fans of scope art...

it's chock full of vintage glass too... for better or worse, I would never have the heart to gut it.

it's on wheels... it's portable.

Polkersince85

I wonder how well these would work. They are coming out with a four channel soon but at about twice the price. Reviews recommend making better probes.

http://www.seeedstudio.com/depot/dso-nano-v2-p-681.html?cPath=174&zenid=a1443ccdd369315eee3f6ae6b94179a0

megasat16

mhardy6647 wrote: »

Solid state Tektronix or H-P would be hard to beat and at this late date the price should be right. Establishing the linearity and accuracy of the amplifiers might be difficult without calibrated frequency and voltage sources. Just eyeballing a sine or square wave from a decent function generator ought to give a pretty good impression of the Y-axis amp linearity. I think making a Lissajous figure with two sine waves of the same frequency (but 90 degrees out of phase) would be a pretty good test - should get a nice round circle :-) http://www.jmargolin.com/mtest/LJfigs.htm

You really don't need much amplifier bandwidth for audio. Good old analog color TV even only required a 5 MHz scope, and the waveforms for NTSC color video are pretty complex.

This is a nice primer on oscilloscope use:
www.tek.com/Measurement/App_Notes/XYZs/03W_8605_2.pdf

Here are a couple of other, albeit more vintage, resources on knowing your 'scope, courtesy of Pete Millett:
http://www.tubebooks.org/Books/smith_oscilloscope.pdf
http://www.tubebooks.org/Books/haas_oscope.pdf
http://www.tubebooks.org/Books/Middleton_troubleshooting.pdf


I'm probably not the best person to ask about oscilloscopes, though :-P

Thanks for the links! I enjoyed reading them.

I wonder who is older. The scope in the picture or you? :biggrin:

mhardy6647

'bout the same (half century give or take a coupla years).

On3s&Z3r0s

Check this out... one relatively local to me of similar vintage. Should I buy? It would be my first piece of tube gear.

http://seattle.craigslist.org/sno/ele/2237643872.html

mhardy6647

Unfortunately, the value in these is the approximately 115 (!) vacuum tubes inside them.
Using one as a daily driver would be about as practical and about as challenging as doing your daily commuting in a Ferrari Berlinetta Lusso.

EDIT: OK, this site says 102 tubes... I never counted.
http://www.thevalvepage.com/testeq/tek/545a/545a.htm


http://www.thevalvepage.com/testeq/tek/545a/valves.jpg

megasat16

On3s&Z3r0s wrote: »

Check this out... one relatively local to me of similar vintage. Should I buy? It would be my first piece of tube gear.

http://seattle.craigslist.org/sno/ele/2237643872.html

Steer clear of it. You'll get more hassle than you bargained for. If you are going to use it, you'll need to understand how to properly calibrate it or pay for professional calibration.

So, just think to get some DSO which is user friendly in your case.

That Vintage stuff is for restoration by hobbyists or for junkies / collectors.

i.e. For someone like mhardy. :biggrin:

On3s&Z3r0s

I figured that would be the answer... they are pretty to look at though. With all the tubes in it I'd imagine it doubles as a space heater. :biggrin:

dave shepard

I hate to say it but if you need to ask how to test it to see if it is in working order you have no need for it because you probably don't know how to use it. I don't for sure and know of only 2 people that do and they are highly trained in electronics repair (one is a retired Mac dealer). I would save my money.

mhardy6647

They're not really any harder to use than any other vintage analog triggered sweep scope. BUT there's a lot to go wrong with one and it's just not the place to start with a silly scope.