Tektronix 2225 Analog Oscilloscope - EEVblog #196

hi welcome to the EEV blog and electronics engineering video blog of interest to anyone involved in electronics design I'm your host Dave Jones hi how could I just score a tech triple to five fifty megahertz dual channel analog oscilloscope beauty always wonder one of these because it is one of only three oscilloscopes I think it is that I know of on the market that has a 500 micro volt per division vertical scale and that's great for um measuring real low noise staff the output of power supplies and things like that so I thought it'd be just a real nice scope to have always got a lot always wanted one and I was lucky enough to pick one up here local these are quite rare to find these in Australia here but in in the u.s. they're fairly common - really nice 50 megahertz um late eighties kind of vintage Tektronix scope and I've mentioned it before you should have an analog scope in your lab you can get them for fifty or a hundred bucks under a hundred bucks fifty megahertz dual channel like this one very handy analog scope to have you know if you're just relying on your Rygel you know in digital scope it's not too bad but then noisy and you know they're just not as real-time as a good analog scope highly recommend you get one so I thought we'd just start I'll do a teardown everyone wants to see a teardown of course vintage teardown do there's a separate video because people like the separate teardown videos and but for this one I will just basically I power it up did I get a dud or not I don't know um we'll pair it up check it out check out all the basic functions so this will be a reasonably basic guide on how to test a secondhand scope like this if you pick one up on ebay chiefly I got this one for a hundred bucks Australian which is pretty darn good now you can pay more than this in the US I was pretty lucky to get this but this should be a reasonable guy just what do I check once you get it is it within calibration do all the functions work and stuff like that so let's pair it up give it a go now one thing I like about the tech 2200 series is a whole bunch of then this one the specific triple to five I've got here is I think there's only one other which has the 500 micro volts per division vertical scale but dump the thing is they're quite small and they're quite lightweight this one only weighs about 6 kilos so if you're buying a secondhand and log scope on eBay in weight can be a big factor because you'll pay shipping costs especially if you're buying it from the US or some other country and shipping it overseas it can be a big deal so this one's reasonably a lightweight in the scheme of things and unfortunately this one didn't have a this one doesn't have the actual up bail on that the the tilting bail tilting handle which comes over because it was a rough mount unit so but that's not a big deal you know if if you need it really portable then the tilting bail is important but some you can pick up a bit cheaper because they don't have the tilting bail on them they come out of a rack a system or something like that now it's a good basic layout dual channel and log scope I really like you've got your dual channel inputs here you've got your horizontal you've got your triggering totally separate over here this has got auto full auto peak to peak triggering on it which is really nice it's got it instead of a dual time basis only a single time base but it does actually have a times 5 times 10 and times 50 mag so it works like a dual time base but doesn't have the full capability as you get on a full dual time base and low scope now let's take a look at the vertical here and you'll see that the reason I like this one is because it has a times 10 magnification most scopes on the market will only have times 5 Verde Verde cool mag so it says up pull cow 4 times 10 mag so if you pull this here and you get this yellow you can notice the yellow there on there so you can tell if it's up pulled out at a glance there which is a really nice feature of this now conveniently it's got two different two different positions here for your x one and your x 10 probe because this doesn't have like an automated probe detection for x 10 that doesn't have menus and all that other stuff we can on-screen display the volts per division if you're using a times 10 probe which you will be most of the time then you take this position over here so you don't have to multiply it in your head you just look at the one that you're using I find that really quite handy and of course it's got all the basic stuff on your vertical that you want it's got our AC and DC and ground coupling on both channels it's got invert it's got an ADD mode where you can add both channels and it's got a subtract mode as well because that's what this channel to invert thin here does if you want to subtract them while you invert channel 2 so you're adding channel 1 plus minus channel 2 which means that you're subtracting them so it's got subtract mode and it's got old and chopped as well and my almost moster scopes have these because it's not a this is not an old-school dual beam oscilloscope this is a dual-trace oscilloscopes and the difference is actually quite significant which a lot of people don't understand this only has one arm one beam inside so it can only project one beam of electrons at once onto the screen so if we put it into if we display both channels here and we here we go now I've got it turned on here it does actually work by the way it seems to at least power up now we've got the dual channels here and we can adjust those like this and let's just start fine now it's on alt mode at the moment what it means is that the a dual-trace oscilloscopes can only draw one trace at a time so it can only draw that one and then that one and this is what alternate means alt means it it alternates between these two traces that draws this one and it rolls that one and back that one and that's really good for higher time-based settings now you'll see this effect if we turn it down to one millisecond per division two milliseconds you'll start to see it very shortly there you go 10mm milliseconds per division is really start to see it 20 milliseconds you'll see it draws that one and draws that one what there we go so that's why you need chopped mode because what chopped does instead of alternating between the two it um it slices it well it still alternates between the two but it does it not for a whole sweep it does it like this it just jumps between them like this you can't actually see it because if you can't see it vertically because it disables the trace during that but it does actually it chops between the two like that all the way across so even at very slow time-based speeds you can get both traces on the screen at once of course that that works up at higher frequencies as well but it won't be as bright and really you should switch to our alt mode if you're up on the higher settings like that as I said one of the great things I love about this scope is that it has five hundred micro volts per division our vertical scale now as you can see on the dial here at only goes demo 5 millivolts per division but it's got a times 10 R times 10 vertical amplifier here and most scopes on the market will only have a times 5 so they'll typically might go to a good oscilloscope we'll go down to 1 millivolt per division vertical scale but this one does better does that twice as good as that at 500 micro volts so if you put on 5 5 millivolts vertical scale and you pull that knob bingo well now I've got 500 micro volts per division which is absolutely fantastic vertical scale it is absolutely awesome I love it now we're going to check out this thing out just just to make sure what it's armed noise floor is like to make sure it's actually are good make sure it's in the vertical scales are within cow that's the first thing we want to check then we'll move on to the rasaan - and move on to the triggering and things like that but let's see if this thing basically works so let's give it a basic check out first thing we're going to do is make sure we get both traces on the display here so I'm going to put it into a dual-channel position off is a good one just sort of mid range on your horizontal time base here you know one volt per division or something like that doesn't really matter and yes we are getting two traces here now we want to test the focus of the traces as you can see it really goes out of focus at both our it's more towards one end but as long as you can actually get that reasonably sharp now that's a pretty good sharp trace I really like that no problems at all and next you want to test the intensity of it the intensity is really it goes up really really bright I like that and basically you want to turn that up to the fastest time base setting you can get in this case it is 500 sorry 50 microseconds sorry 50 nanoseconds per division and that is at full brightness with dual channels up so that's really good and I can't see any screen burn in here because these CRT displays um if if people have just left them on at full intensity then they can get burned in but there's no signs of burning there at all and we'll check the horizontal coarse and fine here so we move it across like that it looks alright there's a little bit of it there's a little bit of a wiggle there I don't know if you can see that let's turn the vertical right up no it doesn't seem to matter but there's a little bit a little slight wiggle there I'm not sure what that is but make sure you can get the full horizontal trace on the screen like that and you can do fine and coarse adjust that looks like both fine and coarse work just fine you want to be able to Center it on the screen like that no problems at all next thing you want to do is you want to test the trace rotation when you buy it if it comes from a different part of the world you may have to do some trace rotation so you want to make sure that works line it up with one of the lines on the screen there one of the kradic you'll Xander it's spot spot on I like it so our focus intensity works our horizontal position works our vertical position works you want to make sure that the line is nice and flattened it doesn't curve you can see it starts to curve when it gets down to the bottom of the scope down there but that's of the display down there but that's fine so both are so that's the channel to position and the channel one position goes all the way up as well no problems it looks like it's working an absolute treat so far and the next thing we want to do is plug in our function generator now I'm using my arm Agilent 3000 x-series oscilloscope the wave gin module from that because that's the highest frequency general-purpose function generator I've got here in the lab so what I've done is I fed in a 1 kilohertz sine wave there it is there's my scope up there and I've got it set to a 1 kilohertz sine wave at 400 milli volts peak-to-peak now the reason it's 400 millivolts is because that will give us a full scale down here on our arm scope you can do it another values but it's just a I just like to get full scale here now this thing is supposed to output 400 millivolts per division my vertical scale here on channel 1 is 50 millivolts per division and as you can see if I put it right down there on the bottom it's just shy of the upper arm marker there so really it's some slightly out of cow on the vertical channel there not a huge amount I'm not I'm overly concerned about that now let's try channel 2 as well let's say it's 50 millivolts per division once again it hasn't triggered from there because it's still triggering off fat channel 1 over here so we need to the source to be trigger to bingo so we are now testing our trigger capability from channel 1 channel 2 looks just a treat we'll have to test our external later but vertical MobileLite just as select select between the two of them basically and we selected the channel to that there we go and not a problem it's a it's reasonably clean and nice I like it and look you can actually see if you're looking there you can actually see the step response of the DAC inside the agilent 3000 series function generator you can let me try and turn that oh sorry wrong channel there we go there we go look at that you can see you can see the DAC you can see the steps in the output DAC because it's a digital function generator not an analog see the steps in it look at that beautiful I like it so anyway let's turn it back and look really high-intensity there and channel two once again it is short um it's it's slightly out of cow but at least it's consistently out of cow on both channels so I have to pop it open later find the adjustment to that pot and adjust the vertical but that's a good enough I wouldn't complain about that too much at all and I've changed the function Jen to four volts per division so I'm now I'm at point five volts per division on channel two and it's exactly the same it's out by the same amount so I really like that plug in channel one here and trigger off channel one let's turn it up and bingo it's out by once again the same amount it's very consistent across there so really I'm I'm quite happy with that and you can test all the scales in the same way you can see that that one is half of the value we had before and so forth so it looks to work a treat on all ranges really I'm quite happy with that and one more check right down at the low end I've set the function gender 40 millivolts peak to peak and we've got it on 5 millivolts per division and once again how by the same amount beautiful I love it it's working a treat and it's relatively oh well it's it's very noise free down to 5 millivolts per division now let's try and not take down a bit further and try this sometimes ten magnification gain now unfortunately my function generator only goes down to 10 Mille volts peak-to-peak and that's not long low enough to test the 500 micro volts per division range which is things capable of so I have built this little contraption here which is our 4 50 ohm terminators are wired in parallel onto the coax here and I've set my function generator to 50 ohms output and just so happens I've got a little Dave CAD drawing here which shows what's going on the function GN is set to 10 Mille volts peak-to-peak and that's into a 50 ohm load because I've turned on the internal 50 ohm load in the function generator so if we had a single 50 ohm terminator here we've actually got four but if you have a single one then we we get our 10 where we get that value 10 Mille volts peak-to-peak into 50 ohms but because we've got 4 in parallel like this it's actually 12.5 R ohms total and if you do the math it comes out two drops it down to 4 milli volts peak-to-peak which is great because we've got eight divisions on our screen here 500 micro volts per division gives us 4 milli volts peak-to-peak full-scale fantastic and here it is it this is not on our times 5 sorry times 10 mag but if we pull it bingo there's the there's our sine wave in on times 5 mag now you notice that it's actually more than 4 million volts peak-to-peak and that is not because of the scope that's an error in our function generator if we go up here and we plug it into our Angelyn up here check it out we actually get yep you probably can't see it there but it's actually four point seven million volts paid to be so the function generator isn't actually spot off we go into the wave generator there ten million volts peak-to-peak there's obviously some error in that as you'd expect when you get down that low and basically we are getting four point seven million volts peak-to-peak I've got the average in turned on there if we turn the averaging off we can actually see that it's a bit noisier than that but you turn the averaging on and beam goes so this thing is our tech triple to five is working a treat I love it now you can actually see when we've got no input down here it's actually picking up a whole bunch of noise on times five um times 10 Meg sorry I'm so used to saying times five magnification for vertical this is times 10 so that's the same on channel 1 or let's try channel 2 oh it's not as bad on channel 2 so if we turn them both on there you a lot notice that um huh what have we got here we've got to add there we go that's the problem there is your problem right we've got alt mode and look at channel 1 is a bit channel 1 is a lot noisier it's got something on there so something's going on there it's not the best when you turn it down you can notice a bit more noise but you turn the time-base up it's definitely got something something on that so I'm going to actually apply a terminator to that and see if we can get that to go away yes it certainly does if we terminate that it's gone so likewise and channel to something sure where that's coming from maybe something internally of course if I put my hair near it on my hand on the control something like that so when you're measuring low noises like this just start it noise pick up is a major issue but um I do deem that to be a pretty decent and working reasonably well write down of this 500 micro volts per division now we have to check out our horizontal as well now we're fitting in my 1 kilohertz signal and I've got it set to 0.1 milliseconds per division 100 microseconds per division and you'd expect to get 10 divisions there but you don't it's actually shorter that so the horizontal isn't uh isn't really a spot on that needs to be adjusted as well if you want to calibrate this thing I mean you know if you just want to get signals on there then you know it's it's good enough but yeah I would I would be tempted to go in there and not tweak that just so that's that's a bit too far out I think I'm not happy with that so I have to what Cal that internally and we need to check our trigger as well of course now so we'll take our trigger level here and we just adjust it and make sure it goes uh make sure it goes between it pretty close to the positive and negative values there and it certainly does and if we choose the negative slope trigger and do the same thing yeah that's working perfectly no problems at all and that's in the peak-to-peak Auto triggering mode we also want to test the normal mode as well so we move it over to normal and we turn it back to p2 peeking the set boom it goes straight in there but if we go to normal mode once we get past that trigger threshold up there it should vanish so yep it does there you go and likewise on the bottom side once we reach that just past the negative bottom of that waveform down there bingo gone and once again then positive and negative and it works a treat so normal mode works as well and we'll check the single sweep mode over here so take it all the way over and we get nothing on the screen this is where you're probably going to want to turn your intensity up like this and then press the trigger button there it is bang no problems at all and a very simple way to test to trigger a hold off down here is to set it to minimum and note the brightness of the trace here and as you turn your hold off control up it should dim like that and that's a very basic test that indicates that the trigger hold-off is working as well and we're going to want to do a quick test on the external input to make sure it works as well armed now that's triggering off channel one at the moment up there but if I turn it down to external here and external and the source actually to our external because this external mode you can choose between the fifty it's live frequency or external / 10 or external or Z input but there you go it's a try and trigger and stable and if I disconnect that of course it loses its trigger works a treat and we'll just check out line triggering here as well this means that it actually gets the trigger source from the 50 Hertz mains earth in the US will be 60 Hertz mines MIT's 50 years so I've set my function generator to 50 Hertz and if I go below 50 Hertz you'll see it's scroll in one direction going across like that and if I go above 50 Hertz it'll go back in the other direction and of course if you had pigs if you had it exactly the same frequency as the main frequency it would actually be stationary but I can only adjust my function generator in point one Hertz increments so my mains here in Sydney at the moment is somewhere between 50 point zero that's 50 point zero it's going in one direction in 50.1 Hertz there you go so it's somewhere in between there so the mains frequency in Sydney the moments probably 50 0.05 Hertz or there abouts give or take I will do a quick functional checking on our LARM trigger coupling up here I've got a AC coupling and it should work on DC in that Peter Peck auto now if I turned over to normal mode here okay an AC coupling it should Dart trigger but on low frequency at my 1 kilohertz test signal it should actually completely attenuate that so there's nothing to trigger on so it should disappear and in high frequency it should work a treat and if you keep it in auto mode then it's pretty much it's still going to try and get a trigger there even with the low frequency filter on but if we put on low frequency or reject filtering and we increase our frequency here then it should eventually trigger at what what have we got way up there its way up there it's a we're in the megahertz region at the moment let me turn that back frequency Jim was a bit overzealous there but if I put that down to it you know that's 90 kilohertz 50 that's 10 that's 10 kilohertz roughly and it's just starting to trigger at 10 kilohertz there you go so it's an order of magnitude thing really so anything over 10 kilohertz this thing's going to trigger on nicely and likewise with the high frequency reject filter it's a 8 kilohertz at the moment if I turn up the frequency on that thing it should eventually not trigger at all let's see what frequency it stops triggering at 50 kilohertz 60 70 80 130 kilohertz still got 170 160 170 kilohertz there you go it's barely triggering now 180 kilohertz and it's stopped triggering completely that works a treat and if you're really keen TV service tick you're like go in and test your TV line in your TV film modes but I'm not going to bother now let's go back to the horizontal here I'm feeding 100 kilohertz sine wave and let's put it onto the old horizontal mode shall we and hasn't displayed anything at the moment that's began it's on times 5 magnification time base that's because we haven't done the trace separation there it is bingo there is our magnified there's our magnified waveform so if we turn that down we can actually out separate the traces like that and actually get both of them on the screen at once so that's our x 5 that that looks like x 5 to me oh I go in there I measure it but it looks pretty good and that's times 10 there it is okay so that looks like it works an absolute treat and we can even go 2 times 50 here and bingo there it is that's the times 50 magnification and of course if we just go over to make here it'll just display the magnified waveform like that but you can do both or just the one so there you go that looks like it works fine I like it and we should actually check that that value is spot on I got times 10 mag at the moment with 100 kilohertz so I'd expect that to be 10 divisions across and it's not it's slightly out just like it is with the main time-base as well but that should come back in once we calibrate the main time-base another thing we haven't checked is the probe adjust here so I've got a times 10 probe so we're actually going to use the times 10 setting over here not the times 1 so we're on point one volts per division it says we should be getting 500 millivolts peak to peak at 1 kilohertz are we well not quite at 5 divisions there so it's a little bit out but not a problem and we should be getting basically 1 kilohertz but once again the time base is out just like it was before so looks like our probe adjust is working fine let's have a quick check of the high frequency bandwidth here I've think I'm feeding in the highest frequency I've got from my function generally chizz 20 megahertz at 4 volts peak-to-peak now armed and this wanted the problem with this Techtron is triple to five is if you use it on standard time base it's just really it's not fast enough that's as fast as it goes okay so you know I can see the 20 megahertz signal there but you can't easily get in there and measure its frequency and stuff like that so it really forces you to use your art it forces you to use the Meg mode which is okay there's nothing inherently wrong with that it's just that not as nice as some other scopes which I have the main time-base which goes down to that but anyway that's okay and you'll notice that it's a bit fuzzy here once again if we go here our frequency is slightly out again of course because our main time-base is out as we're verified before but ER as you can see the amplitude has dropped a bit from where it was before so really you know it's um it's it's starting to roll off there I think now one thing I didn't mention with the vertical is that the bay with the quota ban with 50 megahertz is only four are basically all of your arm basically from your five pillar volt range and up once you engage this times ten magnification here you will actually drop the bandwidth in in the case of this oscilloscope its bandwidth with the times ten gain on any either of these vertical channels the bandwidth drops to about five megahertz so just by an order of magnitude basically so just something to watch out for you don't get the full fifty megahertz quoted bandwidth down at your very low um volts per division settings just a little trap to watch out for now as you can see my 20 megahertz signal looks a bit fuzzy there that's because my intensity is right up and it's causing a bit of a blooming effect on that signal now I you know I don't know if that you know if there's actually something wrong with here and there and there and the triggering is you know there is a bit of trigger jitter or its performance the high frequency isn't as good as it should be I'm not sure I'd need a reference our triple to five scope to actually compare its true performance there but anyway that's more than good enough for my purposes I'm not fussed with the high frequency performance of this thing anyway so now if you wanted to actually test the bandwidth I've mentioned this before of arm any scope really but in particular these are analog ones as you can feed in a square wave and if you don't have a fifty megahertz a function generator that's fine just feed in a 1 kilo square wave with a very much fast rise in full time and you'll be able do 1 C you'll be up by measuring the that's a square wave on feeding in now it's not terminated properly and all that sort of stuff but you'll be able to measure the rise time the rise and fall time of the oscilloscope will basically be equal to the mother bear with the vehicle to naught point three five on the rise time so um that's a way to actually calculate the bandwidth of your analog oscilloscope if you don't have a function generator to go to that I've mention straited that mention that in one of my my goal blogs if you want to check it out and the last thing I'm not fussy about but the beam find yep being fine works now there you go but that's I've done some basic tests on this thing and apart from um some slight calibration issues with the vertical Channel and the horizontal they've drift a bit I should be able to bring those back into cow by our tweaking some pots inside or something like that but yeah I'm quite happy with this at uh it works um it was advertised as working but I took a bit of a risk I don't think they were it was actually showing any waveforms in the actual ad fruit picked up I deem that to be a winner there you go so you know don't be you're too scared to buy these are analog scopes on eBay but one tip if you are going to buy it and you really want to be sure that's working at least buy one that actually shows both waveforms on both channels um like hooked up to just the probe adjust signal or something like that if you if you got both signals on there and showing a basic waveform then you can be pretty sure that it's going to do most of its basic functions and um if it is slightly out like this then you can just start we get back into calibration get the service manual and do that so there you go this is fun and I really like this that that seems to perform reasonably well I'm quite happy with it I'm going to download the surface manual for it and get in there and tweak the pots and have some fun I think see ya

Channel: EEVblog

Views: 164,293

Rating: 4.8911176 out of 5

Keywords: tektronix, oscilloscope, analog, analouge, scope, 2nd, hand, ebay, craigs, list, 2225, calibration, cal, check, waveform, crt, dual, trace, 50mhz, vertical, scale, triggering, horizontal, tutorial, sweep, how, to, guide

Id: 8GR_6QH3uZk

Length: 32min 45sec (1965 seconds)

Published: Tue Aug 16 2011