Hi, you might remember this dumpster find uh from my videos. quite. it's probably a few years ago now. Anyway, I'll link it up here and down below if you, uh, haven't seen it.

It's a Tektronix TDS 540d and it's a four Channel 500 megahertz uh Joby and it actually works, but the CRT in it didn't work. Um, but the I was able to get it working from the VGA output on the back and it seemed to work just fine. It's missing a couple of knobs, but these TDS series Scopes they do have a reputation for uh, having problems um, over the years, but they're still incredibly powerful Scopes Um, it doesn't have a huge amount of memory things, only like 32k or something. four channel? uh, 500 megahertz I think two gig sample uh per second.

You know it's a pretty still a pretty Beastie um scope. So I thought that instead of repairing the uh CRT that I do an LCD replacement for it and this is actually quite a common thing A lot of people do AC CRT replacement for this thing so that's what I've got now. but I'm having a bit of issue with it. Show you what's actually uh, going on here and see if we can solve it anyway.

Um, during my live show the other week, I did actually uh, get this out of the bunker it's been there in parts and I reassembled it and when I first turned it on I encountered a bizarre fault. it didn't work and I'll insert the clip here and it was just, um, amazing what the culprit actually was Flowchart Diagnostic Flow Chart Primary Troubleshooting Procedure: press on the principal power switch. Can you hear the fan? Wear it? No. because I've disconnected it.

622 refers to the flashing code 8 in the right center of the flowchart. Oh thank you. Primary Troubleshooting Procedure: Really? don't miss it does. DS1 First flash dot 8, then display a sequence of hex numbers.

No. Does DS1 Flash 8 then display the sequence of hex numbers, pausing to flash dot C No. No. Replace the A11d Ram processor display module.

Obviously, displaying the eight is the first thing it does. and then it just resets and keeps flashing Eight Eight. So it's clearly not been allowed to go through its sequence. So like, change the entire processor board because you get a flashy eight.

No, No, No. I'll I'll plug the fan in just for that authentic fan noise. I Don't think it's detecting the fan. It's only a two-wire Joby But you could detect that? Who knows.

and that'd be embarrassing if it was. Hey no, it's now working. It was the fan. Really? Whoa, Yeah, it's flashing.

It went through a cycle. all all the leads are on. It's now flashing top, bottom, top, bottom, top, bottom segment. It boots maybe.

I Don't know. Is the Dallas SRAM in this thing going? Let's try and prove that I'm going to disconnect the fan. It's the only thing I'm going to do is disconnect the fan I'm going to turn it back on I Think it'll work I Reckon there's something else. a foot.

No, it detects the fan. There you go, it detects the fan. Wow. I Would not have guessed that it is.

It must have some circuitry to detect that the fan is connected because it's not like a it the fans. only a two-wire jobby that that made a fool out of me. I would not have guessed that. Who else would have guessed? Be honest that it was detecting the fan and that was causing it to cycle boot.

Although the fan does plug into the processor board, there's a bit of a bit of bit of a giveaway. it plugs in the processor board, not in the power supply board. So there you have it. It was the fan on this thing which is this giant jobby over here and as you can see like it's it's only a two pin physical connection on there.

so they must be doing some sort of like load detection to you know, determine that there's a load on the fan. So if I boot it up without the fan here and you can see, it just flashes the eight and the front panel just flashes off and on. It's like it's like at the power supplies hiccup in it's doing uh, something like that. Um so yeah, it's really weird and I don't think this is actually covered in the main, you know at all actually I haven't tried this.

Can I just plug the fan in, Will it? Yeah. Look it. just as soon as I plug the fan in, it goes I don't know if the four is correct. it hasn't fully booted yet Like that.

when it's good. No. I'll just turn it off so we'll just boot that up. There we go.

it's gone through its uh, Power on. yep and then it'll eventually reach a point where it should just yet toggle up and down like that and it's working now. of course. this uses uh, some Dallas non-volatile uh memory.

and what's the date code on those 99? So they're 22 years old? So yeah. Ah that's a bit of a problem. Um, but anyway, it still seems to work I'm not sure if they hold calibration data or whatnot. you can see there's some missing memory here.

Um, this is actually for the color option I did actually buy some memory. this is way back when I was in the old, uh, that big rented lab that I had and I was looking at doing this. I did actually buy the memory and I've got it somewhere. but it's you know, hidden away in a box somewhere in the bunker.

So um, yeah, I'm not going to bother with the color upgrade until I find that I just want to get the LCD working. So what I've got is this: LCD here I'll put up the data here. it is a generic type, but apparently this is the one that fits the TDS or alert. At least that's the info I uh found on the web interwebs? um, somewhere.

and yeah, it just came with one of these Uh boards which has a VGA Innovation by the OCD on its own. But or you can buy it with a Uh board. and unfortunately, I'm getting a bit of a problem, so let me power it up. so check it out.

I Don't know if you're seeing that, but I've only got one way for on there, but there's more than one because it's got multiple colors. Have a look at the font down here. you can see that it's got the different colors there and they're on, like alternate lines or something. There's some sort of like interlacing type problem or something like that.

There's something going on there, but it does work. Interestingly, if I turn on the menu system, it does it with the menu as well. Auto config. That's not going to fix it.

So oh, there we go. No, it just moved it up to the top. There detects it fine, but it's doing some sort of weird decoding of that. And now given that it's got different colors and this is only a mono output first of all.

and then I will, uh, disconnect I think um, two of the color lines and see like if we just get the one color and it's it's fine I don't know I've got a slightly more modern scope. My Mdo3000 has a VGA output and that looks fantastic. There it is. so it's something particular with this: uh TDS 540.

Yes, if you're wondering what that display is there, that's a safe operating area. uh display I've been playing around with it I might maybe I'm gonna see a video on safe operating area anyone? Beulah and I've got another LCD here, but it's the wrong form factor I'm not sure where this one actually uh, came from. It works just fine and dandy. So there's something with this board that's um, in particular with the signal from this.

uh, TDS 540 but this board um I don't know. jst ping or something works just fine. So yeah, look, it's beautiful, but it's the wrong form factor and no, the LCD cables aren't compatible I Don't think what we want to do is disconnect combination of the colors. so we've only got one color so like it'll just not get the other colors because it's We're seeing multiple color lines there so if you just get rid of one I don't care if I have a green screen.

In fact, that will be quite retro. If we go down here, we should be able to see some RGB inputs and a bingo There You Go 75 75 75 should be three of those. Yep, Okay, so that'll be red, green, blue input there and I'm sure if we buzzed out that point there, that point and that point that would go over to the RGB. So which one's which? They do actually have a VGA connector under there by the looks a bit nice.

Okay, yeah, so you could have put it like a VGA directly on there. Red, green, blue. There you go. So you've got a squared C and you've got grounds and you've got your vertical sync your horizontal sink.

Let's leave the middle one intact. Let's leave the green one intact. Shall we or is the input come in here and going through this zero Ohm resistor I'll just buzz it out 75 ohms to ground. That's shorted to the fourth pin down there.

Yeah, the bottom side of each of those 75 ohm resistors is grounded. So the zero Ohm resistor could be the input. Let me try and find it. She's the buzzers loud on this son.

786 When you've got a dead, silent lab here. zero There You Go Fifth Pin One, Two Three Four five. So if we take out the zero Ohm resistors Bob's your uncle, top zero and resistor and the bottom one and that should just leave us with green. Sorry, you can't see this I Want to get it vertical? Got him? Okay, let's give that a ball and we can't see that of course.

So as I've shown in a video, just get a light. Got a little my little load here and look at that magic. Check it out like it's just just absolute magic. You don't need a polarizing filter or any of that rubbish.

So uh, SSD 102 star. Oh look at that. It certainly is green. but um, nope, it's not.

It's not solving our problem That was kind of obvious, wasn't it? But I do like the green I like that retro look I think I might keep it if I can fix this damn thing. Wait, hold on to your hat. I think I might have fixed it. Look if we go through the menu here in here, they're actually there's this thing called clock I I had it on D It looks like it has a B C D on D we actually got something look but it's not very bright.

Oh yeah, it doesn't show up on camera that well, but that looks good I think I just need to maybe play around with that clock and then adjust the brightness. Yep, we're good. So there's something with that clock set in. Let me play.

Oh, there's a few lines over here, but that is actually usable in its own right. It's just not very bright. Um, maybe I could put the other two colors back and it might be good. but uh yeah, I'm going to play around with this clock setting now.

Don't there you go. I Set it to clock A and that looks absolutely fantastic except the brightness is still quite High Look at that. There you go. Oh I like the green I'm liking that.

Tell me I'm wrong. That looks old school I Love it. I'm not going to put that back so that that's fixed. That's all.

It was dull obviously. Um, there you go. So there it is. So I don't know what that clock setting does.

It shifts the clock and it's I don't Yeah, don't know if you know. leave it in the comments. Couldn't be bothered investigating that, but that works. Hunky dory.

look at that. So I'm now going to try and hopefully retrofit this in here. It's supposed to be the model that actually fits, but uh, we'll find out anyway. you get the bow for the top Boards out.

You've seen this in the previous videos and that's where all the LCD um CRT stuff used to go. Um, and the VGA cable of course will disconnect that from the back and we can just plug the cable in and I can just have a short cable or don't know about the cable solution yet but somehow it has to mount in here and this pulls off and this has got a little ribbon which goes over. that's for the buttons of the front and there you go. so we have to somehow Mount this screen in there I'd Just I Just love the magnesium alloy body on these things.

It's absolutely beautiful so all that has to shove in there and uh oh, that's upside down. All the electrons are going to fall out so this has to somehow get in there like that and mount on the back of here. So oh, that's a pretty good fit. that's not bad, although you can see it.

You could just put some black tape on there I guess just to cover up the metal a bit. Oh no. Well, I don't I don't know once you put the front cover. I Actually the front cover? Yeah, once you put the front cover on there I don't think you'll notice that.

Yep, just Center that in there and just tape that tape that in place I think and Bob's your uncle? Um, yep, you just need to line it up. Potentially minor problem here. Our board requires uh, 12 volts DC input. And by the looks at this sticker here, all of our supply here is.

um, it doesn't. There's plus five and there's plus 15 and you know, minus five and stuff. but no 12 volts to tap off. Um, there could be like a 12 volt on a board.

Somewhere like the plus 15 might go to the board and there might be a 12 volt. uh, reg on one of the boards. Maybe we can tap it. It's just annoying, all right.

So this is my plan. I've stuck my uh PCB on the back of the LCD in here so the LCD is stuck in there. so that's hunky Dory. I've actually added the control board up here.

so I've stuck that down so that it should be able to access because the PCB is just in here. I think this is just vacant, uh, space. and the power cable? Uh, because we've got the floppy drive here which I haven't got actually connected. Um, the connector for that is over here on the edge.

I think there should be 12 volts on that shouldn't there. And then my VGA cable I'm just going to have that curled up I'll stop it flapping around in the breeze in there. and then the uh VGA cable here that will come up there and go in there just putting some tape on there for the sharp edge. and uh, that should just sit in there.

it should just connect up there like that and Bob's your uncle. Um, that's the plan. I'll give it a bill. Yeah, it really needed some sort of black mask around the screen there.

so I haven't figured that out yet. but uh I don't know. Yeah, I might replace that later. It turns out I had to move the control board because this metal actually uh, is a fit under there like that.

So the power cable and and that I don't know that might have to sit on the fan or flap around the breeze or so I'll figure out some way to do that. I just wanted to have it outside so I could actually play around with it after the fact, right? So I screwed this plate back in place and I I've mentioned this before I Do like how these Uh supports this is the hard drive. ah board I Don't believe it runs the Um OS I Think it's just. uh, storage isn't it? Yeah, that'll just sit in there and then it just slots.

it pushes back in place and locks. It's really, it's really very nice. Now we'll put our processor board in place and I'm sure I can get 12 volts from somewhere on here. there's our VGA connector plug that in.

No workers. Then we put our little interconnect board in here. There is a third board that goes on top. you can see there's another slot there I Don't know what the Third optional third board is.

that's rather tricky to get in, but it's in nonetheless. Side ribbon cables which I really like. and then we've got this side interface board over here. Beautiful.

look at that so that'll take the Uh, just higher frequency signals over does it. So rather than just the IDC ribbon, so there. and we're going to plug the fan in otherwise it's not going to boot and the VGA is plugged in and then this is the printer output I think isn't it? Oh, is that why the fan? It knows it's uh, not there. Um, it's a smart fan control temp.

So uh yeah, that's just not I don't think that's an ordinary fan or is that a pot? No, no, that's a temps and temp sensor. Yeah, it looks like a control temp. Looks like, yeah, 45 degrees looks like um, yeah, All right, something smart about it. But anyway, we do have our control board now so we can just, uh, stick that down to the fan.

No worries. and uh, all we've got to do is get 12 volts into this sucker. So I've got my well I can just measure things or I can just check the manual I'll see if we can get the pin out for that. Oh no, I found it.

Um, it's got some yeah, convoluted ribbon which goes over. so I have to take that Shield off and try and get it back in right? Let's just turn it on temporarily. So I've got the plug pack actually connected. Let's see if I've got it all connected in place.

No sync. It should take a bit. Yeah, it looks, uh, quite. It is a bit offset.

That's not just the camera angle. Well, partially the camera angle. There you go Tektronix TDS runtime environment: It's not hugely bright, but I can increase the brightness on that in contrast. No workers, so that works.

Yes, I did change it back to uh White sorry yeah I did like. just in case you want to do the color upgrade option or there's some sort of you know, shading or something like that. For the insta, you know the DPO mode or something like that. hey, that is not flesh flashing anymore.

Ah, can't cop a break bloody. Murphy Although I didn't see a light, come on. I didn't hear a clunk or anything. It's just, um, a ribbon so it looks like it's custom thing it's gonna work there.

Nope, it stopped again. What? Seriously? Seriously? I haven't done anything. she re-powers and it it works. but um, no, that's not my tripod on the wrong angle.

Um yeah, don't use gaffer tape to hold in your screen. It's not better than that. I was probably going to take it off anyway to do the black surround thing, but it now works. So yeah, um, it's not very bright so I can call that up.

but yeah, I don't know, like like four or five times in a row it didn't work but now it's working. so I I don't know like is it non-volatile Dallas SRAM going like I I don't know it's the hard drive going that requires because I can hear the hard drive spinning up when it boots and you know it's trying to access something. I I yeah I don't know. All I've got to do now is um, we'll fix that and um find a uh 12 volt uh point.

Now the way you are way I would find a 12 volt. Point I've got the menu I've got the service manual. Maybe it's got some voltage, uh, test points or something like that. but I'd be looking around at Caps.

Things like these are tents down here. You can see these tantalums right which will get oops scooped up. my focus there. head on.

manual. um yeah. look at um, caps like this and uh, ones that are like high voltage rated. Could be it like you could get like a 16 Volt or a 25 volt? uh, you know, tag tan or an electrolytic or something like that.

these are all tag tents on here. There's no litros at all on here actually, but there's a few Tay tabs so I might just go around and actually measure those and we might get lucky. We might actually get 12 volts. I mean down here is near the floppy Drive which I've still got disconnected.

No, that wasn't it. Um, by the way. so yeah, maybe there's uh, 12 volts around there. So I might, uh, check out that see if I get lucky.

All right. Do I feel lucky? Let's have a squares. five volts nude. 5 volts? Nope.

3.3 No, these are right in the middle of board. These are all going to be 5 volt. No, it's the one right near Cartage over here. No, not a sausage.

Anyway, pretty confident I'll find uh, 12 volts on the uh hard drive board here. So and then it's easy just to bring the wire. Under The Other Board and uh and just solder it on. No wuckers.

Unfortunately, you turn it on with this board and all you get is hiccup in rails. It's all you get. So yeah, that's that's. no good at all.

Um, it's almost as if it doesn't. You know it needs the logic board to switch it on. so we'd like to switch the to keep the power supply switched on it. you know, switches it on the logic board it's supposed to I don't know, send back power, good signal or something and then switches off and hiccup.

Hiccup. Hiccup. Well, it turns out that the optimal position for the LCD actually fits with inside the existing rubber. Yeah, you can kind of sort of like push the rubber to the side a bit and it kind of sort of fits in there.

which is, uh, pretty much the ideal um angle like actual placement within there. So yeah, it's not too bad and it looks like the LCD is like practically the exact height of the existing plastic in here. So you could actually like, um, you know, get a custom fitted, you know, plastic backing on it or something like that if you're really, uh, you know, if you're really Keen Now at this stage, I Thought it might be easier just to power this board from, uh, five volts, but unfortunately, Well, the the outputs here are 1.2 volts and 3.3 As you'd expect for a a, um, you know, custom Asic Like that and the input is actually sure enough, 5 volts. Okay, so we don't need our 12 volts in, but then our LCD over here.

that's actually 9.8 volts. So yeah, and that's probably coming and from that would be derived from the uh 12 volt input. so we can't just bypass that and put the 5 volts directly in. I don't think that's going to work and I just checked the service manual I found a service manual that was searchable for the D model here and I searched for 12 volts and nothing comes up at all.

So I don't think there's a single 12 volt rail in this entire product, wouldn't you know it? bloody? Murphy All right. So what I'm going to do is I'm going to use uh, one of these little TI converter modules. These are little, uh, 12 watt jobbies. uh, more than enough and uh, you could.

it's a 5 volt input to adjustable output depending on what a set resistor is and I just got these in the junk bin in my parts cabinet and well, yeah, I'm going to just use one of those. so a single resistor on there 5 Parts in. that'll give me 12 volts out and then I can just solder it to any point on that main processor board. Really bugger.

It looks like the shot I just took over on the other bench actually powering up the uh little uh brick DC to DC uh converter. Um, just five volts in 12 volts out. It was hunky-dory but I don't know the camera lost that clip. it was corrupted or some rubbish I don't know.

um I think the battery died or something. Anyway, I've got the wires coming out here. he shrunk and then I've just got them going into two uh, header pins here and I actually found ground and five volts on uh, pins like like three and five there or something like that. Um, so yeah.

so I found my five volts so that goes into the Dcds converter that's all hidden behind there and uh, let's try and Power It Up shall we right? So I think I've got that around the right way. otherwise the magic Smoke's going to escape. I got my 12 volt uh DCd 5 to 12 volt DC to DC converter in there and it should power up. So let's go What? Gone up to seven on there? Yep, obviously getting power and will it show that problem that we were having before? We've got flash flash flash flash up on the lead display up there.

It's going through its boot cycle though. It froze after this, didn't it? I can't remember exactly and that has booted. Uh yeah. I need to shorten my obviously not low conductive enough to uh, clean that but and get that menu off.

but that's a winner winner. Chicken dinner. Work that front panel back on can operate the buttons. We've got the sloppy back.

Connected Although I don't think I ever tested the floppy. no idea if it works. there are modern. Uh Replacements you can get solid state replacements for the floppy I believe.

Yep, there we go. That's got to click into place. Really a bit difficult to get these front panels off. There's a bit of a knock to it.

There you go. like a bolt one and here it is. Cover back on does actually pair up and it seems to work. so I have to run like you know, feeding signals.

but I fed in test signals before and I think all four channels worked. Um, so yeah, it's all hunky-dory The screen isn't as bright I'd like. if you turn the brightness up, it just appears like like the back light and it fades out and stuff. so you know it's okay.

but it's You know it's nothing to write home about. Anyway, the good part about it is is that it is functional. It says channel One there's a significant offset actually Channel 2 significant offset so I might have to run through. The three's got an offset as well and four right after it is a couple of more traces in there.

I've got some math waveform on or something. Let's turn DPO mode on uh, which works better in color of course. but then it drastically drops the memory. Uh, yep, that just turns it back off and we can put in dot mode.

Yay cow down here. Signal path initialized. can we hit that? Compensation corrects for DC and accuracies That's what we want caused by temperature variations. long-term drift yep, can run anytime after the oscilloscope has warmed up.

Okay, so I'll leave it warming up for I think it's 30 minutes and then they claim re-run it. Um, if the ambient temp Has Changed by more than 5c or once a week in vertical settings of five millivolts per division or less I don't know what the front ends like on these really drifty I don't I don't recall um, them being that bad. Don't recall ever being an issue for the older ones I've used. Not yet.

Yep, there it goes. I'll just run it just to see if the DC offset goes away. Who cares? if it drifts again, you can just rerun it as many times as you want. Well, that's finished.

And yep, that fixed the DC offset issue as you'd expect. So yeah, no workers can we change the vertical on that looks good. We can go right down to one millivolt per division. Not a problem.

So there you go. That was an interesting upgrade of a Uh Tektronix TDS 540d. And as I said, there is a color upgrade available as well. You have to uh solder in the extra RAM chips and do some other mods to it I can't remember what they were, but unfortunately I can't find those chips I've got them in a little baggie somewhere down in the bunker, but you know it's in the last lab move.

Yeah, they've come and got so and uh yeah, you know, be nice to get some new knobs for these things. But anyway, I got plenty of Scopes here in the lab I have no use for this one. so I'll probably just um yet I don't know, sell this. um, auctioned it off or something and no, please, please do not leave comments down below.

Oh I'd love to have it I'll pay for postage. trust me. I'll pay for postage. No, you don't want to pay for postage for this thing.

and no, I don't want to ship it overseas. Sorry, that's just the way it is. Okay, shipping these things is a pain in the ass. so I'm just gonna do it.

Uh, I'll just uh, probably just you know, sell it locally I started at 99 auction or something. maybe after all it was found in the dumpster, but um, yeah. four Channel 500. uh Meg bandwidth I'll double check that two gig samples per second and I think that, uh, halves, doesn't it? Anyway, I'm gonna put like the minimum of effort required into this to just to tell people what it is and I'll probably just auction this thing off or something I don't know.

but uh. anyway, if you found that video interesting, give it a big thumbs up. As always, discuss down below: catch you next time.