DR #8 - Tektronix 2213A Oscilloscope Troubleshooting and Repair Part 1

hey everyone its Nick welcome back to another duality repair video I have another scope to look at tonight it's a Tektronix 22:13 a 60 megahertz analog scope and I got this off eBay again for parts so there's something wrong with it see it's got some pretty good condition physically all the knobs and buttons are there none of them are cracked or missing or show serious signs of wear at all well there's a few stickers on here and some residue general scratches and wear and tear on the case but nothing too major the screen looks to be in good shape see there's a sticker on there that says Pegasus lab that caught my eye it's kind of curious so I looked them up it looks like there's a company called Pegasus laboratories in Florida does some sort of chemical testing and R&D work so I thought that was kind of interesting but anyway there is something wrong with this I'm not quite sure what it is so let's turn it on and have some fun alright the scopes plugged in but before we power it up I noticed a few things I guess just one thing it's trace rotation here just an empty hole and I looked further in there with a flashlight I don't see any adjustment pod or anything in there so I don't know if that's missing or for some reason that's just an option that was not included on this eye that seems like it should be a standard function so I'm gonna have to open it up and see if that's missing at some point I'd be kind of a bummer especially if the trace needs the rotation needs adjustment so one thing to note before we power it up so let's plugged in what's powered on and see what we have so I'm on the both channel 1 and channel 2 right now and well the intensity sure works and certainly only see one channel right now so let's go to channel one that looks like I'm seeing channel 1 huh so I'm toggling between channel 1 both and channel 2 and that beam isn't moving at all so let's change positions that's not right either let's change oh man there you go okay the time scale knob was really stiff I thought it was just completely it seized but probably just hasn't been cycled in a while it seems to be working okay density works really well so we do have a beam but the vertical position doesn't work oops a vertical position for channel 2 works when I'm using the vertical position for that channel so let's check channel 1 alright it was working it's needed to do the beam fine let's do both yeah it doesn't look very good let's see a little better hmm on a tough time triggering once got both beams up see they're both in AC let's try the Chop there we go okay now we're looking pretty good channel one is adjustable vertically channel two is adjustable vertically so everything right now looking okay question is are we gonna get a signal so let's start with channel 1 and maybe I mean I thought it was broken at first but maybe it's just I've never seen a probe adjust I guess it's just a pin hole like that instead of the prong that sticks out certainly see a change there let's change the volts per division thanks a little ugly that does not look like a square wave should be 500 millivolts peak to peak at 100 or 1k Hertz 1000 Hertz 500 millivolts so we should easily see something right here at 0.5 or smaller interesting what happened they're not looking too good channel 2 out see if we get anything different on there again I'll go to 0.5 since it's half a volt peak-to-peak I'll go even smaller 0.2 channel 2 here that's what I want to see yep channel 2 looks good so looks like our problem is with channel 1 not reading the signal correctly or really at all so I point to I should get the same signal as they do here I got nothing nothing at all well of course not one channel 2 yeah it looks bad that looks bad so we have a single channel failure and other than that you know everything looks to be good again I'll have to figure out that trace rotation but as far as major issues yeah channel 1 channel one's no good so this does have the service manual available so I'll I'll pull that up and take a look through it look through the schematics and then see what kind of the relevant schematics I might want to look at and print those out and we'll take a look and areas we want to focus on alright so I'm glad I played around a little bit more with the channel 1 volts per division dial there before I opened anything because take a look at this so at 1 volt per division we have a nice square wave and you know you get a little bit higher and it gets a little dicey but very nice at 1 volt per division you go to point 5 and it looks pretty rough right and later let's see if this makes sense so 1 volt per division it should be half a volt peak-to-peak so if one division is 1 volt then we should have about half an half a division so we're yeah that's pretty close so what happens when we go change the scale to half a volt it gets pretty ugly its name with 0.2 but I noticed as well its 0.1 and you go right there so you can still see it you can see the bottom of the square right here you just can't see the top because the the scale is so big and I wonder if you can see it well we can do this too we can move it up and down yeah so you can see that there and if we go down to 20 20 millivolts per division you can see it there it's getting a little rough and 10 I'm not seeing much there yeah you can see it there too so it kind of just looks like we might have a dirty dial to the rotary encoder there so go back to one and of course it's no it's not reading nicely at one oh that's go say it's messing with the fine adjustment see if that'll help here really so I'm not gonna worry about the schematics at this point I'm gonna open this up and see how easy it is to clean this uh just knob here and the rotary encoder that might be our only problem while I'm in there I'll take a look at this trace rotation and see if it's broken off or it's not supposed to be in there or what the heck is going on there so yeah we'll figure it out here before I move on to opening this I think it's worth noting that I figured out there is a pot back here for the trace rotation and it's obviously working they just for whatever reason decided to make it recessed by oh that much well three quarters of an inch to about an inch so it is back there it is working so I'm not gonna worry about that just gonna worry about these cleaning these dials off so let's get it open the unit's out of the case let's take a quick look around so we have our power supply section hidden in here it's definitely better protected than the 22:05 I just worked on they have this nice shielding case I'm sure both for protection as well as for noise mitigation then of course you have the seer CRT up here and the high voltage cable leading from the power supply section over here we have the front board so your front panel board that will distribute your signals like position vertical position horizontal position triggering things like that and then down below here we have our attenuation and suite board so this is going to relay our signals for our channel 1 channel 2 vertical deflection as well as our our time scale through these so these are actually for the fine tune adjustment so you can see I can rotate this one that's the fine tune for channel 1 channel 2 vertical deflection and then here's the fine tune for the time scale and then the main vertical deflection adjustment is going to be under here and you can see the main vertical time scale is right here but I know that these are slightly different so we'll have to pull this cover off to take a look we also have the main board on the bottom it's one big giant board and of course Tektronix makes it nice and serviceable pull it out and it's it's all it's all exposed right there very nice very nice so I don't think I'll have to be doing any work on the main board here at least not yet get started on cleaning cleaning the channel one vertical deflection so I'll take this cover off and we'll see what it looks like underneath alright so in order to expedite the troubleshooting process let's go through this channel 1 volts per division knob here let's go across the entire dial and identify and characterize exactly what the problem is so that we don't waste time looking at parts of the circuit that aren't relevant to the problem so I am fully counterclockwise and let's hook it up to the signal so with you know it's such a small signal it's it's not gonna look very well with the trigger but it is showing just fine at the 5 volts per division here at the x 1a probe so let's turn the dial clockwise and and see what we get each time so at 5 we're good at 2 we're also good again the triggering isn't great there we go it's still not triggering wonderfully but you can you can definitely see the square wave so I 5 were good at 2 we're good at 1 volt we're still good ok when we get to the point 5 volts this should be a really nice looking square wave okay we don't have that there point 2 volts same thing we should be able to see it it would probably go off the screen in one or both directions but we would be able to see it easily and obviously it's not there so 0.5 is bad my two is bad it's checkpoint 10.1 also bad right so all three of these 0.5 0.2 0.1 are bad let's go to 50 mil 50 mil is good so it's huge but it's they're seeing it very nicely let's go to 20 20 mil also there and then 10 also there I can't even scroll to it but you can see the vertical lines there 5 same ten cities dropping off there there we go 5 mil same 2 mil you can also still see it low intensity but they're all the present their turn intensity back down our issue is going to be with point one point two and point 5 volts per division only and that will come in handy and it's extremely relevant for the troubleshooting process so keep that in mind Oh point one point two point five all right I have the cover removed from the attenuator sweep board and so you can see these two rotors here are the controls for the channel 1 channel 2 volts per division adjustment so let's zoom in here on channel ones rotor so you can see what's going on so what's happening here is that you can see along this rotor there are these little nodes jutting out and what these do is as you rotate they either press down or they do not press down on these little Forks and so when the node is not pressing down on that fork there's tension on the fork that allows it to be raised and to be elevated off of the PCB as you rotate and the node pushes it down it makes contact with the PCB so this is what's allowing for different circuits to be activated as you rotate it now looking at this two things a I don't see any sort of corrosion or carbonization any build-up on any of these contacts I don't think this is a contact related issue and then the other thing I notice is I was worried about maybe we love lost some of the spring tension in some of these little Forks here but I checked continuity and all 16 as they were down and they all made they were all continuous so I don't think that is the issue I think what the issue is is part of the circuit itself that's involved with the three volts per division set points I think something in those parts of the circuit is as faulty so one thing I had to do was the reason I went over earlier which set points where faulty is so that I can help categorize which of these forks may be bad and then which part of the circuits they correspond to so so as you'll see this is fully clockwise this is 5 C here fully counterclockwise this is 5 volts per division as I rotate through to 2 volts per division and then 1 volt per division only one of these Forks changes in between each all the rest are the same so within each area of adjustment only one fork changes between the two so now when I change from one volt per division to half a volt which is our first problem area you get several of these other Forks change ok and so now when I change within this range from 0.5 to 0.2 again we only get one fork change and from point 2 to point 1 again only one change so then when I go back down to another scale another range which is 50 millivolts I get all these Forks changing again so these are grouped in ranges and there are three ranges of three set points so I did a bit of work there are 16 Forks along this control here and the only two that are common between our faulty range of 0.5 0.2 0.1 volts per division and uncommon - all of the rest of them is fork 6 and 49 ok so I look really closely at these I didn't see any buildup on and I verified they are making contact when they're supposed to with the PCB below it so what I think we need to do is pull the schematic for this sweep attenuator board and look at the components that are in the circuit making contact with fork six and fork nine and then we have something to go after you know maybe there's a resistor in line or capacitor in line something that's not behaving correctly which is why we're getting basically no signal in this range so I'll pull up the schematic we'll take a look I have the attenuator board schematic here and specifically I have it zoomed in on the channel one portion of that schematic and you'll see I have some things highlighted here I'll explain that in a second but what's important to identify is that this whole section right here is the rotary switch and so if we look on the board here that's this okay and yes I did remove the board I'll talk about that in a second so let's zoom in on that a little bit so we started all the way on the left we can see that we have our millivolts per division labeling so two five ten all the way up to five volts and then I have 100 200 500 millivolts per division highlighted because those are the three set points that we were having issues with it's in all the way this works is you can see each of these columns is labeled 1 2 3 etc all the way up to 15 at the end and so in the previous segment I described I said there were 16 Forks or contacts but I either miss counted or their labeling or their counting two contacts together as one and so it's one of those two things and so you can see that these dots here in each column the dot represents contact and no dots represent no contact so when the when the nubs on the rotary dial there are pushing down on the contacts that's represented by these three dots or these dots I should say three dots in this case all right and so I spoke last time about commonality between these three set points and which contacts have commonality and so you zoom out a little bit we can verify that the only two contacts that are common to these three set points are these two right here the ones I have highlighted you can see this one there's they're not even making contact this one they're making contact but so are the rest of these set points this one the same thing they're making contact with the rest of these set points and etc the only ones that are common are these two little two men back on these so you can see contact five and contact eight are the only two contacts that utilize the 100 200 500 millivolts per division and the previous segment I think I called them contact or fork six and nine and so since I miscounted or whatever they're labeling them differently I was just off by one so where do these lead these lead up to this attenuator this 10k attenuator attenuator to here and so basically attenuator is just two capacitors you can see there's two knobs with c1 and c2 c11 excuse me in c12 and so these are just two capacitors inside this attenuator here and this is a custom package manufactured by Tektronix and so first thing I did before I remove the board was I adjusted c11 basically all the way in one range and all the way to the other didn't change anything I adjust the c12 one range all the way to one range of all the way to the other and it didn't make any difference I just said they're both at the same time didn't show any difference to the signal so I don't believe I don't believe that adjusting this is going to fix the issue and so unfortunately I think this attenuator is what's causing the issue basically these two capacitors in line in this one package the other thing I did was I tested I tested for shorts or opens between the capacitors and to ground I didn't see anything different between this attenuator here and the one down on channel 2 so this is channel twos here that's the way they have it spread out so attenuator fifty-two is for Channel two I compared continuity between all the pins on this attenuator on channel 2 and channel 1 there was no difference so what I'm thinking is one or both of these capacitors either have there's some sort of issue with this attenuator it has to be because there's nothing in line but the between contact 5 and contact 8 and the attenuator there's no resistors capacitors any other passives in between here and this is the only difference between our 100 200 500 millivolt and the rest this is the only difference there's no difference at all the rest utilize you know similar parts of the circuit there's all there's commonality between other parts of the circuit between these 3 set points and the rest so it has to be this attenuator that's causing our issue so let's take a look at the board I removed it and so we have channel 1 here channel 2 you can see these resistors off here on the right those were they're soldered on the back and then they were soldered to the input connections well I just D soldered I'm gonna remove the board so if we're looking at the board here we have the 2 attenuators right here and so look a little closer you can see 10 X on the top one and 100 X on the bottom one so this is our attenuator that we're gonna have a problem with and they have the Tektronix part number right down there 307 - 10 13 - 0 0 and I looked it up yeah you know they're they have references to them all over the internet but none of them not nobody shows them in stock except for one person in greece on ebay and it was $7.00 so i bought it that's the only one i could find $7.00 plus 8 dollar shipping from greece yes greece I think the 15 dollars is well worth putting into the scope since this seems to be one or solely the only issue on this scope I think it's well worth it with the price I paid for it putting fifteen dollars into what I'll be able to get the scope up and running and so since its from Greece it's going to be two to three weeks before I get this thing in which is why I'm making this part one I'll make part two when that comes in when it comes in I'll remove this I'll install that will verify that our issue is gone on the 100 200 500 millivolt per division set points and then we'll also verify the functionality the rest of the scope if there's anything else wrong with the scope will attempt to address it at that point so I will be back with part two when I get this attenuator in and we'll start by installing it in part 2 thanks for watching we'll see you next time