EEVblog #1203 - REPAIR: Tektronix 2465B Oscilloscope

hi it's vintage tech scope time you may remember these somebody sent these two classic Tektronix 2465 scopes once the original 24 65 and once a 2465 be the coveted 2465 be some say many say the best analog oscilloscope ever made argued down below in the comments now my recent visit by a Nobel laureate Barry Marshall if you haven't seen that video seriously even if you don't think you'd be interested in hearing a Nobel Prize laureates story trust me it's really good everyone who watched it thinks it's absolutely fantastic I'll Lincoln it at the end anyway he's a tech a vintage tech a buff as well as having a Nobel Prize and he's actually got a 24 65 B and he he loves these things that reminded me the 2465 the two of them that I've got here sorry to whoever sent this in I forget your name it was a couple of years back I've had these sitting on my shelves in the background in my mailbag segments for quite some time and they both are scrapped units but I thought I'd pair them up and see what the status is because I can't remember I think one of them had a power supply hiccup the other didn't this one has no trace written on the inside of it and it's scrapped and the both of them don't have cases on them but I thought it's worthy of actually having look see if we can fix this I'd much prefer to get the the newer one the more modern B Series one going because it's 400 megahertz as opposed to 300 megahertz I do like the classic blue screen on this I don't know why this is the red this like like Marone kind of color it looks yeah I don't know I just don't like to look at it much prefer this one down here so I'm not sure the history of that change or not in the graticule changing like that anyway if you do know please let me know but absolutely classic scopes and they're worth taking a look at and yes I do I did upload the video on the second channel the Tektronix the ancien it was a 465 or 475 and that's a sort of like in progress repair but if I'm going to spend the hours on it I'd probably rather spend some time trying to get the 2465 be fix so let's pair it up have a look now if you have a look inside both of them this is the newer B model this is the older one you can see no trace scrapped somebody's written that on there and they're basically have equivalent power supplies they look absolutely equivalent they have the same interface all that sort of stuff but of course this one looks more modern because it is and everything looks very similar between these units but this one the older one does have an extra card on here I believe that's entirely integrated in the processor board on this one but apart from that they are very similar now as far as the main processor ball goes I don't even think I need to tell you which one is the more modern one it's obvious with all these surface mount down the bottom and look at all the beautiful through-hole resistors on the top though look at that that's just a thing of beauty it's joy forever but anyway the new modern b1 it's all surface mount another through-hole rubbish and what's the process for an SC six seven one two what's that I'm not entirely sure anyway yeah the Delos semiconductor that in non-volatile 119 this is a thirty second week nineteen ninety so we're talking near thirty years now so geez yeah that battery will be no good but anyway that's the least of our concerns now so we're looking at getting a trace up and running on this thing and the older one is ninety four vintage you're gonna well they're the roms eighty eighty four eighty four sorry I was looking at the head that's looking at ninety four ninety five there and I thought jeez that's pretty recent no the other ones eighty-four Wow okay nineteen eighty four and you can see the numbering on the chips as well 1984 so yeah it's quite a significant difference there so on extra six years and an updated model that makes all the difference and as for all the analog stuff on the bottom with all the customized these custom heat sinks every one of these is a custom job' there near-identical there's a few differences like you know immediately spotted like this down here like it's got a little ground link and a one resistor this one's got a ground link and a couple of diodes and a bunch more resistors but apart from that you know that layout this one's got an extra trimmer in there does it there's yeah there's a few differences but largely the architecture is very similar so maybe they could so obviously I could possibly use one as a parts unit perhaps so definitely if you're gonna repair these having obviously to be ideal to have a cell like the same model but should be able to at least salvage some parts if we ultimately need to on the from the a unit so I'm all the tech buffs out there and by the way no I am NOT going to consult I should if you're going to repair these I highly recommend you consult like the Tektronix repair yahoo group and stuff like that they will be screaming at me during these videos that oh that's obviously that capacitor there it's all that Doya that transistor fails all the time everyone knows that well yeah okay I'm just gonna wing it sorry can see small little changes like these have a discreet whirring just going to headers from the controls the nobbies on the front where is this one over here the newer model looks like it has that flat flex on there so just some you know sort of tidy up improvements in terms of manufacturer ability from the side near-identical as well these board has changed but the functionality hasn't the wire and sure the Warrens even all the same so yeah there's just change see don't change the pots over but it looks similar all right here we go I'm going to pair up the new 2465 be a lot of people will recommend i pair it up just going to automatically change all the caps and yeah okay okay here we go all of the lights come on that's good will they go out I do remember when I used to use one of these babies they used to come on as a pair on test but they ain't going off no it shouldn't take that long you can see it that's nicer know anything about his past life I don't really have any test points marked as such no voltage is marked on their terrible Muriel yeah we have some crop circles I'm not saying it's aliens and I can't see any marked voltage test points on this board maybe there is one I've missed it but can't see diddly squad I'm sure the service manual has it all covered but geez you know put on a silk screen please all right do we have five volts on our board let's go across a random chippy yep four point nine seven five hours all right presumably that's why all our LEDs are lighting up because they'd be under logic control just for kicks let's plug in the the older 1984 was it 85 yeah 84 83 model let's go it's hiccup in I hear something hiccup in tick tick tick tick this scope will self-destruct in 10 seconds now upon a closer inspection of the board check this out we've got some corrosion on these parts around here that's a resistor of these two caps I reckon these electrodes they are looking pretty sick so Eric and they've spewed their guts everywhere hmm there's the same cap up on the other end of the board that looks a bit crusty rusty too so yeah I suspect all those caps are gone well you're not going to believe it all of the test points voltage test points are on is 14 pin dip socket here who would have known a j1 19 yes I had to read the service manual to find out although if you follow the money those pins down in there they actually I what go through to the power supply board on top but they're not really labeled anything you can physically follow them so yeah really you had to RTFM to know what these are supplies aren't sure enough in our service manual ridiculously comprehensive I'll link it in down below crazy anyway let's measure all our test points so these are all the and not in order which is kind of annoying but these are all our different rails on here so let's measure those we already know the digital +5 old digital seems okay I'm not measuring that Ripple yet I'm just making sure they're in the ballpark okay pin 1 minus 15 that is minus 15 surprise surprise pin 2 at digital plus 5 already measured that yep it's good for is Plus 10 volts bang-on look at that well least significant digit out but come on minus 5 volts 6 plus 15 Wow that is bang on 8 plus 87 volts now we're getting high bang on ridiculous surely one of them is gonna be filed 940 2.40 p 2 points 300 it's a little bit low it does tell you the tongs on here by the way it is within tolerance 11 is - eight lucky last analog plus five on twelve Wow winner winner chicken dinner all of our power supplies on this fine and dandy doesn't mean you wouldn't go in and fix the caps or anything like that but all of our lids on the front just on so it's not going through the sequence I might read the manual and see if it says anything about LEDs stuck on but yeah anyway we do know we have some dodgy caps on there and that non-volatile SRAM that's got to be Gonski by the way you might be able to see down in this power supply there's a reefer madness capacitor down in there or the effect there's two of them you see another sneaky one down in there yeah I'm gonna want to replace those but right at this moment no yeah I need to solve the digital problem now as it turns out there's actually a whole set of comprehensive tests when this thing powers on there we go and they are indicated by not only on the CRT like as in text on the CRT but obviously our CRT isn't working here in fact we're being fined not zippity-doo-dah nothing's readout intensity nope so no no good even a scale illuminations not working so yeah no that's one sick puppy but anyway I'm they it does a kernel test first like basic kernel tests and errors indicated by various LEDs lighting up on the front panel but I don't see and then it goes under more routine like more thorough tests of all sorts of stuff but and I can't see anything where all of these are lit up it doesn't say anything about that in the manuals so are they actually on or they just bleed through from the other it can't really tell it does take time so obviously the process is doing something because the process has to drive the Oh or something on the screen there did we yeah look got something Wow okay that's well yeah alright it doesn't say anything not that I could find about all the LEDs lit up so yeah is up the RAM so I'm just gonna measure the ripple on the 5 volt digital because that's all we care about at the moment so working on ice seep in to the spec is a hundred and 50 millivolts peak to peak ripple and we're getting my 350 millivolts so yeah 5 volt rail it's got a lot of ripley on it that would explain a bit ok I just want to have a look at that ripple with the scope we're at 200 millivolts per division so yeah there's your problem we're only supposed to have 150 milli volts peak-to-peak so our ripple is absolutely enormous whether or not that's causing an issue I don't know but that's really not even in the ballpark compared to the total spec there so yeah you'd probably want to fix that first before troubleshooting further I'm gonna say they getting this power supply out of here is pretty horrible it does actually slide out if you undo some screws at the bottom there but then some of the wiring especially to the voltage selection switch on the back they've got little Spade terminals they have to be lifted off the board in this direction but they're hidden behind here and to get these it's just a it's a mess don't like it big strapping earthly there how you doing oh and there they are they don't looking good Nick we go this looks just looks old cracked or whatnot yeah I'd be just sucking those out as a matter of course anyway what we're really interested in is the 5 volt rail here because we want to solve our digital problem first so that's going to be our 5 volt main supply under there there's our big DC input filter cups after the bridge rectifier because this is a switching converter obviously yeah and there's another sneaky bugger down in there and yep that's genuine reefer madness and there's a thermoelectric mechanical switch in there for measuring the temperature of the powertrain ease on that heatsink of the casings on look at that three powertrain is there anyway that's just in short that'll just Auto cut off the supply where if that heat sink over heats now of course a really annoying thing about this is that the connectors are labeled on the silkscreen you know you've got your JS fine but as I said there's no voltage test points like oh well there's no like voltage marked test points or anything like that but all of your capacitors these aren't labeled like you know see 100 or whatever you've got to actually go and get the service manual and schematic and get your board overlay which is like okay well fine okay the manuals ridiculously comprehensive like hats off they just don't make them like they used to absolutely fantastic but yeah you've got to go in and get you overlays so it's kind of it's really annoying anyway what we're interested in here is our five volt regulator here it is and see and our output caps see 1280 that's our 5 volt rail okay I like this that it's labeled C 1280 like this to match our Q 1280 up here they label them in sections that's a trap for no cities I think I covered that in my good schematic design practice video didn't I if I didn't well it should have been in there yeah like match them Group label like this cuz you know if this was Q 1280 and this was C you're a 101 or something like that it you know it's just not as nice have to match up anyway so we will check our output cap but also because the ripple this isn't going to be a magic ripple rejection here we're going to look at this one which is the +5 volt unrig here the printout didn't show it so we jump over to here and sorry for crudité of this but if you have a look at the 5 volt unrig down in here i think it's that one c1 15 there so we got a 250 mic cap down in there so that's the input side to the unregulated one so we want to check those two caps they're probably dead as a dodo so c1 15 there it's that puppy and which is different to these ones these are brown ones these are probably lower ESR ones so this would be a 5 volt cap that's our unrig cap and the other one and then c12 80 is there so we've got a flippity doo-dah and c12 80 which one is it ah that puppy there but because they're all identical like that you know if you got one fail you would also a suspect and measure the others and a lot of people will go and go hole bugger it I've got the board out I'm replacing every single a little electrolytic in this thing it's like it's already like what is it 35 years old or something and yeah I don't blame you so I don't know if I want to do that I just want to get the 5 volt way or I just want it to sort of see if that's causing the problem of like not booting up so to speak so one side of the board flips out here and wow look at that burn mark from that regulator isn't that terrible Muriel yeah well it obviously gets hot but there's no indication that that one's failed at all because all our rails are measured just fine so no worries anyway I want to suck out that I'm just going to measure it first if we can measure anything in circuit and anything funny business and we'll get that out and they've got a shield between here as well which is actually connected but yeah more or burn marks down on there or somebody's header hang on is that a Harry hacker somebody's are they they just hand done look there's a bit of a hairy hacker down there with the they look budge Don and they're all the flux residue doesn't look like any of the others were they done by hand at production time I would be I don't know maybe hmm anyone know oh no check it out look the row of these caps here we think that one's failed on the file a suspect get that these ones are fine these are got the original wave soldering on them that ones are hairy hacker so as yes I want to go at this okay we'll just do a crude in-circuit ESR here at a hundred kilohertz so it's oh sorry it's just one over here this is our five volt one this is our suspect one point three point two seven ohms that sounds pretty good let's measure the other ones which are all identical type and value for point two nine yeah that's good that's good there you go so they're all the same so oh hang on it's got a pierce through the flux there it's where you need sharp probes there you go so all those ones look they're all the same so you know you wouldn't really suspect that you might suck it out and give it a more thorough test but I would say that one's okay so that that's the output capacitor the output of the regulator so the other one is this one here 2.9 almost three ohms so I suspect that one might be cactus that would explain it the pre regulator one so yep let's suck that out Wow something is very wrong here I suck that out and it's only a 10 microfarad a hundred and sixty fault cap Nippon chemi-con but what the what what it's supposed to be a 250 Mike like and you don't expect like 10 volts or something this is ridiculous I definitely have the correct capacitor look there's two there there's a third one up there is two here a third one up there see triple 1:5 like what this is the same board I'm sure this is the same board the heck's going on well you're not gonna believe this there's actually an error in the manual believe it or not whether or not they're fix this in the ear adder in later versions I don't know but see triple 1/5 + C double 132 it looks like they're swapped on the overlay here because I was tracing out the board here I was like I was tracing out I'm supposed to go to this at 5 volts was supposed to go to this inductor over here and it didn't make sense it was going to this cap here and it was just it was crazy so yeah they've actually swapped these two caps so I googled this and sure enough yep up comes the eevblog forum how would long who's a longtime contributor on there he discovered the same fault as well and yeah the the bloody service manual is swapped so there's nothing wrong with that cap of course measuring that sort of ESR for a 10 microfarad 160 volt cap is just fine so that's the 5 volt job' there so that's the culprit I need to sort of that back in and suck that one out unbelievable and that dodgy little sucker which somebody's heard had a hairy hacker at 25 ohms at 100 K in circuit so yeah it sucked that little turd out and is that an original or not I suspect not and she's about 20 2 ohms out of circuit that's too high and 1.5 micro farad's 1,500 Dana first reunified fanboy see yep how to explain our poor pre regulation on that thing and of course all that ripple has to do he's dropped on the floor that ripple is passing through the regulator onto the output and back at 100 Hertz 142 Mike yep that's no good for a 220 Mike that's why under it's gone ski now I've replaced it with a just a generic one hung low brand 330 Mike 25 volt cap and well yeah I know I shouldn't do that but that's all I've got at the moment so the lab is an absolute mess I just want to get something back in there that's going to get that five volt rail operating again and just for now I want to put it back in I won't bother replace in any other caps in it just looking at the five volt rail one thing at a time and of course you wouldn't do this if you're experienced with these sort of things you'd go art like you'd have kids that just replace all the caps and see you know like stuff like that in this ol bitty gear but for the purposes of this video please do not comment about this down below just for the purposes of this video I want to see if just changing that one cap makes a difference okay let's see what happens I haven't changed any of those leaking electrodes on the main digital board just wanted to solve that power supply problem so here we go now lights are different lights come on no come on before there they're all on again bummer okay well that could still be the the electrodes on there so let's have a look at the ripple all right we're 200 milli volts peak-to-peak again power on whoa no it's still cactus that's no good so I sucked out that secondary cap or I did like the output cap 0.2 2 ohms that sounds pretty good that's what we had before so let's go to let's change our frequency back 100 microfarads and that's - oops off-camera 100 microfarads that's what we expect so that caps actually in good Nick it's an itchy con alright so I'm going back to these other caps here which have all been sucked out so let's have a squirt like I'd I think I might just go in there and replace the blinking light somebody something could be are bleeding over to the other to the 5 volt rail but I can't really see how but anyway hmm ok I've actually replaced all the caps there or at least all the major one so let's switch on and it something's it's hiccup in look check that out there we go that's progress ha ha hiccup empowers like he could you got hiccup okay I'm gonna capture the five volt rail again there it is whoa that's two volts per division as you can see it's starting up to four four and half volts and then it it basically just shuts back down and it repeats every you know second or two so that's very interesting going from a work well working in quote marks oh oh hang on look look it's gone through itself test hang on it's not hiccuping we have a trace whoa what that I just went away for five minutes to have a look at the manual came back and it went through its power on self test we know so I'm not sure what that hiccuping was there might be something else a little bit dodgy in there that was tripping the some sort of over current protection but wow we're in like Flynn look at that look at race we've got trace we have no display hang on readout yeah we hear we have some readout - wiener it's all fuzzy though look at that I don't like that is that some is that some jitter on the readout but hey it went through the power-on self-test let's try that's bad that's bad hang on whoa a thing of beauty is a joy forever look at that Bobby does like we release the magic smoke yes it's a brand new cap I put in and yep PAP cake I put it in backwards don't look at that isn't that just gorgeous insert meme here wow that's just fantastic but just spewed as guts right out there Oh well son yep dumbass Dave put it in backwards there's a positive and there's their negative the reason I didn't see it is because I was looking at the board from this direction here and I thought that positive was that one I just was not paying attention at all so there you go that explains the hiccup in when we didn't have hiccup him before of course when you had a nice stable power supply Alby it we had a large ripple on the five volt rail and we but all the met all the measurements were spot-on there was no hiccup in at all before and then all of a sudden we were changed the caps and it's hiccup in that doesn't make sense power supplies only hiccup like this when they have over current situations so yeah it's obvious this thing within backwards it was drawing a large amount of current and it was causing this shorting out that rail effectively or loading it more than it's a protection current and the power supply was hiccuping he got he got hiccup that's what good power supplies will do when they have over current protection though they won't just like shut off their winges blow a fuse they'll try again and he gets shut er down try again etc and yeah the magic spark escaped brilliant lucky I've got another one anyway yes these are one hungar brand low sr caps I've put in here I don't recommend you use these for long term but as you can see it does the scope now powers up and we got out of trouble so except I put it in backwards dull anyway I'm going to go in there I'm gonna replace some of the ex caps as well while I'm at it there we go got two new x-class caps on there nice so and there you have it reefers reefer madness so yep yeah definitely if you've ever find these in gear I've done a video on this reefer madness just simply replace them don't even pair it up with these I was a bit you know it's a bit gun ho by the way for those who are wondering about the scorch burn mark around there there's nothing wrong with that transistor I believe seems fine it's just that it's got an as some things in the 2465 be getting notoriously hot I'm not sure if this is one of them but obviously over time it's just browned the fiberglass browned is that a word charred the fiberglass or whatever so it if the thing wouldn't work if that was Gonski so yeah obviously it's okay so I'm gonna leave that for now unless you know specifically that yeah something going wrong there let me know you can see that we've got a similar thing happening a bit of char in here yes I'm going to clean up those joints don't worry about that yeah from these diodes aren't these power diodes obviously getting a bit warm ski and just you know over time just degrading the fiberglass that's all nothing to worry about if your diodes are fine okay after that peb cake I've replaced all the unrig main rail caps and the reason the unrig ones are going to fail more than the regulation or the output side caps is that the input side caps the unregulated ones are susceptible to more ripple so therefore they have a harder working life the internal the ESR is going to cause them to heat up in more internally and they're going to have a shorter life than the output caps that's how it works in theory anyway so I've replaced those I've replaced the X&Y class caps in this thing so let's pair it on again Gemma it's going through it's going through it's going through it's going through and bingo we have that trace again but we still have the fuzzy digits that could be caused by once again there could be like an output rail cap or something on that but yeah that's a it's a nice bright trace isn't you know that so that's pretty sweet nice actually nope that was just our focus there that was just our readout focus I was a bit taken aback because the I forgot that it had separate controls for that and so there you go now readout is beautiful no intensity fantastic and it looks like we've got some cursors here sorry about turning the lights off here but it does actually look a lot better like you can because these little LEDs are a bit a bit wimpy they always have been on this on these art model tech scopes I've never been a big fan of them horizontal position control works channel 1 channel 2 fantastic I'm really liking it and remember I haven't replaced those caps which look I haven't measured them but they look to have leaked and spewed their guts out maybe corroded some of the nearby components on the board on the logic board but hey it's working it's working ok at the moment beautiful no I don't recall these if this is normal I don't think so look press a beat rig and like a whole bunch of a whole bunch of the leads sort of light up that could be some of that those decoupling caps on the logic board might be doing something funny but it's obviously still operational because it's got it to do and to put the text on the screen like that it basically has to be fully operational from a basic point of view so yeah it can anyone let me know if that's normal doing like oh look at that yeah no it can't be no there's got to be something else something yeah look you're pressed actually any button looks like any button no said that oh yeah maybe I can just see him flush oh listen others realize Oh aah Bobby Dazzler and this has got 50 ohm input impedance too nice I forgot we can like turn on where's our other stuff we can turn on the readout intensity the scale factors beautiful look at that now I got it all ah yeah there we go whoa it's a little bit fuzzy a little bit fuzzy but jeez I'm not gonna complain about that that's for sure yeah that's what this the readout here the readout dial you can actually get it to go one side and it just shows the cursors the other side shows the readout and the cursors so then I'll show you your volts per division ah Wow just kind of power that up again it's running through its self-test so the non-volatile Ram I mean isn't I thought that was supposed to like give an error or something if that we if that didn't checksum so maybe there is a little smidgen of battery life still left in that puppy anyway let's feed it a signal well channel one seems basically functional I'm feeding in a one kilohertz 500 milli volt peak-to-peak 484 millivolts on the cursors there you know you're not going to complain about that so that's alright no worries and we've got 20 megahertz there 50 millivolt signal and yep no worries and the same on channel 2 as well 20 megahertz signal 50 millivolts that's working just hunky-dory so very happy with that that's a 1 volt 20 megahertz yep beautiful so there you have it I'm gonna call that quits right now for this repair video it's gone on long enough this is only part one of course I don't consider this fully repaired or fully refurbished or anything I would probably go through on replace if you're properly refurbishing this and you wanted to use it over a long period of time be confident with it you'd replace every single electrolytic capacitor in there I still have no idea about the digital caps on here what you know function they actually performed if they're Foley haven't even measured them I do know that they look like they're spewed their guts and by googling that does seem to be a known issue with other 2465 czar those electrolytic caps on the logic board do actually fail and they corrode away everything but as you can see we've got a fully functional process it doesn't look like it's lost any of its calibration stuff so it looks like that Dallas non-volatile Ram is still just hanging in there by the skin of its teeth of course you can't measure the internal battery voltage in there because the battery is actually internal to the SRAM chip it spotted in that big black block on there but yeah you would replace that as a matter of course like a long-term thing you'd fully recalibrate this and that's a be whole video on its own right fully testing every function and recalibrating this but there you go by we kind of got a bit lucky on this one just by replacing a few unregulated side electrolytic caps on this as well as there's some X&Y Class AR Rifa caps which in this case hadn't failed but they could spectacularly explode it any at a moment's notice and it it has come good there you go so same ax so much for scrap and no trace on this thing um it was simple power supply but looks like somebody's had a shot at this because some of those capacitors had looked like they had been hand soldered and replaced so yeah I'm not sure what's going on there but look at we're on our way this is absolutely terrific so yeah I expected more problems with something like this and of course I did take the easy way out by simply replacing all of the caps on the unregulated outside inputs without really you know like measuring the ripple on all the other rails I just replaced them as a matter of course and it just came good so we've got a bit lucky that there weren't any other faults no faults on the high voltage side of things I really expected a lot more fight with this thing in terms of getting it up and running I thought maybe for this part one video we'd at least get the processor sort of not you know at least trying to go through a sequence it up again and trying to get like a Power on error or something like that because in non-volatile rams god or those capacitors have gone or something like that but geez look at this this is actually functional it looks like it's basically functional scope right now we've got our wire cursors we've got our delta time I haven't played around with the time yet but there you go let's have a look at that there you go 50 odd no no seconds that sounds about right pretty happy with that that's just fantastic times 10 magnification it all seems to work hunky-dory so yeah pretty done papi the new ground on the channel 2 here seems to have a little bit of a little bit of a little negative wiggle there I'm not sure what's what's going on there but the trace has recently sharp more than good enough and all the readouts work can't believe it there you go so something a bit more exciting the cast but we did get one blow up so that was pretty exciting I guess anyway um yeah let me know what you want me to do with this thing for a potential part 2 video but for now that's a part 1 of the repair I guess so if you liked the video please give it a big thumbs up and as always um that's I'm sure there's plenty of tech experts on the EEV log out for them and they'll tell me all about this no doubt about it either on the forum or in the comments down below so that's pretty impressive for a 30 watt plus year old scope and it's been sitting just on my mailbag shelf and all it needed was you know her brand new set of caps by the looks of it pretty remarkable yeah anyway I Q down below about whether or not this is the best analog scope ever made uh some people say also 2467 instead of the 65 yeah yeah yeah go on go for it catch you next time [Music]

Channel: EEVblog

Views: 131,673

Rating: 4.9464822 out of 5

Keywords: eevblog, video, tektronix oscilloscope, tektronix 2465b, analog oscilloscope, oscilloscope repair, refurbished, repair, service manual

Id: Rp-0FqxQkBw

Length: 41min 1sec (2461 seconds)

Published: Mon Apr 22 2019