Hi. take your mind back to 1983, early 1983, and well, what were you doing back then? Well, you were probably watching. uh, Return of the Jedi which had just came out. probably watching War games.

Absolutely brilliant. And what sort of computer did you have? Well, you probably were thinking in the business world you had an Ibm Pc because the Ibm Pc came out in 1981 and it had just been selling like hotcakes for a couple of years. But there were no Ibm clones back then. So what did you want in 1983? Well, of course you didn't know.

Cpm was like going the way of the Dodo, and Pc Dos was becoming the operating system of choice and Cpm getting long in its legs. the Osborne Portable Computer and the other Cpm uh, computers. You know, it was pretty clear that Ibm was probably going to be the future. So what did you want? You wanted an Ibm compatible computer and you wanted it portable.

Who delivered? Compact delivered? Check it out. It's the Compact Portable Compact. Famously founded by three employees from Texas Instruments who decided to leave Ti, formed their own computer company and famously, once again, on the back of a paper napkin, they sketched what their computer would look like for their new business. in a pie shop no less.

And a couple of years later, Bingo. In March 1983, they released the Compact Portable Computer like this, Isn't it Brilliant. It is the world's first Ibm compatible computer. It was pretty close to being Ibm compatible.

The amazing thing was is that Compaq realized well, Ibm have released everything you could buy the Ibm Technical Reference manual. You could get all the information. I've got an Ibm technical reference manual somewhere. damn it.

It's probably down in the bunker after the move Anyway, could have shown you that. Maybe I'll get it later. But anyway, Ibm released all the technical specifications for the Ibm Pc. so it was pretty trivial to make an Ibm Pc clone.

But the sticking point was that Ibm held copyright over the bias, so you couldn't just copy the bias and make an Ibm clone. So what Compact famously did is they had, uh, like a team of engineers not look at the bias at all, like work in a clean room. and basically, well, a metaphorical clean room. A code, clean room and duplicate the functionality of the Ibm Pc bias.

And they were the first to do it. And that's what they were betting on. Big for this company. And it paid off for Compact because they made 111 million bucks in their first year, which is like a U.s business record or something.

and they may have record business sales the next year. Bigger than any other company in American history for like first year startup sales. It was absolutely incredible and it all came down to this Compact portable computer. So what we've got here unfortunately is not the original.

this is the Compact Plus which came out a couple of years later, but the only difference is this one supposedly had an internal hard drive. but what did you want Back then? you wanted Ibm compatibility so it could run Ms-dos Because in a stroke of genius from Bill Gates, he kept rights to be able to sell Uh Pcdos as Ms-dos to other manufacturers and Ibm went well. what's the we don't care if you sell it to someone else who cares where Big Ibm and well, the joke was on there once the Compact came out and of course everyone went nuts over this thing. It was.

you know, a cheaper, better than the original Ibm Pc. And it was portable. You could fit this under the airline seat of a plane. only way 12 and a half kilos.

don't know. it is in pounds for you yanks. Um, multiplied by 2.2 roughly. anyway.

Ah, let's check it out. The Compact Portable Computer: The world's first Ibm Pc compatible clone and at the same time, Ibm released the Pc Xt, which is basically the original Pc but had like hard drive. It really wasn't, uh, that much of improvement. just like the Uh Compact.

Plus here, it wasn't really any major changes from the original Compact uh, portable. just like internal hard drive and stuff. Anyway, this bad boy sold for 3590 Yankee Bucks had 128k of ram expandable to 640k. No one will ever need more than 640k of memory said Bill Gates.

I had a nine inch green Crt. none of that color rubbish. Even though it had Cgi color graphics adapter in it. Uh, classic Ibm Pc.

Uh, equivalent 8088 running at 4.77 megahertz, so it wasn't particularly faster. It wasn't until years later that Compact started coming out with their Uh Des Pro models. did Compact actually release a 286 machine before Ibm did. Before that Ibm actually led the industry.

But it was Compact. Who then later in the Des Pro models actually went well. Bugger this. We're not waiting for Ibm to release it.

We're going to release the Compact Desk Pro and we're going to have. It's going to have the new processor and it's going to be faster and it's going to be better. And they and from that point on, the industry just left Ibm in their dust. So anyway, normally we turned on.

before we take it apart, we have to get on. We have to get on. We have so much time and so little to do. Strike that, Reverse it this way, please.

But I am actually keen to power this thing up and see if it still works after all these decades. Maybe maybe not. Let's find out. And as you can see, it looks like they've kept the exact same keyboard layout of the Ibm Pc there.

And of course, the Ibm Pc layout changed over the years. But the 10 function keys and the mysterious scroll lock key? it's all there. But anyway, Dual five at full height, Five and a quarter inch flop isn't on that half-height rubbish. Um, yeah, there's a floppy missing from this one and this one here is flapping around in the breeze.

So yeah, I don't hold out much hope not that I'm gonna have a five and a quarter inch boot floppy. Maybe somewhere in the archives? I don't know. Anyway, let's plug it in. First of all, check it out here.

This bad boy was actually portable. You can these. I don't like these little dicky latches here, but anyway, you could actually fold this and this was actually the bottom of the case. that like th this like there is no external case for this thing and you pop it up like that and bingo.

You've got your portable, your 12-13 kilo portable computer like that. and around the side we've got our mains input and there you go. There's a serial number for those playing along at home. I don't know the date of this one exactly, but it is a compact plus and then they've just got a couple of feet on the bottom like that.

They can fold in and out, but basically you just carried it as a like in the case is the actual carry case. It's great and this is supposed to be another slot. but bucket. If I can get this to da I'll figure it out.

All right. let's see if this bad boy still boots or not. Here we go will the magic smoke escape fans going? Whoa. Yep.

Something blue? Well yep, yep. I can smell it. Damn. Hang on.

Well yeah, that was dumb wasn't it? Um, should have done the tear down first and uh yeah, just replaced all the caps as a matter of course, but it's not as fun. So anyway, yeah, I'll leave the uh purifier running for a while and just, uh, get all the magic smoke smell out of that. So on a replay of that footage, you could see sparks coming out of here. You no doubt saw that.

But yeah, where the? It's got to be like the mains power supply most likely. Although it could have could be like a low voltage uh, side thing and electro's or tag tents. Who knows, Reefer Madness? Maybe we've seen that before. Anyway, let's try and start taking this apart.

I can't see any obvious screws, so anyway, I guess we'll find some. But as with all Ibm compatibles, Tada, there's our slots. It's our Cga video card external monitor. So maybe even if the internal uh monitor doesn't work, Uh, we could even a composite output there.

Uh, three unpopulated slots. So yeah. oh it is actually uh, pretty obvious why there's no screws on this thing. Obviously these top and bottom panels, you can see those in there.

they are actually just pop right off. So hopefully this should be like really easy access. Well at least you know prod the internals. but when you have to get the boards out and stuff that could be a different which we will to obviously, uh, replace some caps in this thing, that'll be a different matter.

So yeah, you can actually get these off, it's not the easiest thing. These clips are a bit dodgy. Geez, that's a lot of shielding. No wonder it weighs a lot, but uh, geez, I have to take all that out.

Oh none of that Phillips rubbish. Oh Flathead, all the way with Lbj. There you have it. Well, this is interesting.

Uh, the sparks. I saw them come predominantly out of the drive there. So that would indicate because there's like holes through this metal work here as you can see. Um, that would indicate that it comes from this board here.

but that looks to be the Crt driver board. That's interesting. I mean, you know. Obviously, the main power supply is over here and that is covered by this huge shield here.

so I can't see how like any of the light from here would have got over to here and then escaped via the uh, floppy drive. So maybe the primary supply over here hasn't failed something on this side or it could have been. Um, there may be something in the drive? Who knows? I don't know. You'll notice that the floppy drives here have little rubber baby buggy bumpers.

Um, and they're down the bottom of the case down there as well. You can see them how they sit on those so little uh compliant mounts. That's nice. Well, this is supposed to be the plus model, which is supposed to have a hard drive in it.

And maybe they did actually replace the second floppy in here with the hard drives. But as you can see, that's been removed. There's the Cga Vdu card for those, uh, playing along at home for you video card aficionados. Of course this is all made in the Usa, Usa Usa Compact Computer Corp.

Copyright 82 Wow, let's try and get it. What of what day codes have we got on here? Okay, we've got 11th Week 84 there, so it's got to be somewhere in the early to mid 84s. 8420 Got a compact, uh, Asic there that's uh, manufactured by Oaky. That's interesting.

So is that some sort of custom gate array? And of course, your 6845 fanboys go wild. It's the classic, uh chip. There's the video memory. You don't get much.

It's only Cga. None of that Vga rubbish. Ah, I was always a Hercules man. Yeah, we're dating this one about mid 1984 for the video card.

and this connector here is the one that buggers off to the Rcrt driver. so that'd just be your Rgbs and your sync. And of course, in these older computers, you always suspect these little tag tantalums. They're infamous there for going out of focus and also, uh, exploding in flames.

but they're obviously looking good. But if you do want to restore these machines, then yeah, you'd be looking at replacing the tag tents. A few floppy aficionados. Here's the floppy controller with a bit of analogy goodness going on here.

And it's the printer board as well. So we've got our printer output and this bug is off to your floppy drive. and well, there you go. That's it.

Smc and a genuine pin lift barge. Thank you very much. Dang, I think these front and rear covers are identical. I do like symmetry.

Anyway, we have a day code. Um. August 1990 Blur Inkblot is that a four? 1994? I think August 94. Well, looky what we have here.

This just fell out of the machine that looks like the burnt part of a tag tent. So yeah, we're gonna find one somewhere. I'm sure. I really don't mind this uh design at all.

I was able to access the screws for the floppy drive in there. I want you to take the two cards out of here. One of them. them's a short slot by the way, but it is dedicated to the floppy controller so I guess no wackers, this should just slide out.

Oh and power. and ah Shazi ground. but ta-da there is our floppy full height job. The belt looks in uh, pretty good nick and you can see the uh timing chart on the top there.

I'd be surprised if this bad boy didn't still work, but uh, we did see a flash. Did it come from in here? Not sure. Have to get the cage off World storage technology assembled in Hong Kong Must have come out with a cargo plane full of rubber dog? Oh sorry, that was 1986. you screw up just this much, you'll be flying a cargo plane full of rubber dog out of Hong Kong.

Yes sir. Well, as I suspected it wasn't going to come from the floppy. In fact, I don't see any tag tents there at all. Uh, so no it.

The big flash must have, uh, come from the other side of the cage, elsewhere in the computer and just you just saw it come out of the uh, floppy drive. So yeah, it looks in pretty good nick actually. for the stepper motor aficionados made in Japan, all this stuff's made in Japan even before 1985. So now I'm actually, uh, looking down at the through these slots here onto this board.

Can't see any black marks at all. so maybe the flash came out somewhere else. Um, but anyway, now I'm wondering. Well, I'm suspecting that this Crt cage if I take out a couple of screws here and here and on the back side over there, I reckon this whole cage will just lift out modular.

Well, that's a bugger. Take a look in there. I've got a screw there. I can get that one out, but there's another one deep in there.

I might be able to get that one out, so that's annoying. anyway. X-rays Be careful. you'll note the date July 84.

it's just something kind of weird about being able to see your keyboard through the back of the case. Hmm. There is some possibility of lifting this Crt driver board out I suspect. But yeah, it's not the best design.

Anyway, yeah, this cage, it doesn't like. it almost comes out there. You go. it's having a wiggle wiggle wiggle.

Yeah, but the screws are down in there. It's oh. come on. Okay, I think what the deal is is, I've got to get out the switch assembly here, and once I do that, I should be able to get down in.

well. I screwdriver through the case, get into that screw and that one there, and I should be able to get the Crt out. Oh, they've left enough lead length on that. Ah Potter.

Look at that. I wonder if Potter is potted. Um, Ul listed. thank you.

Very much wonder if there's any reefer caps inside that that that's welded shut. Oh, come to Daddy. Yep. Oh, look at that.

Ah, bloody couple of cables attached, but you can see. Yep, it's all modular. Brilliant. Apart from that, well, no, I'm going to de-rate it from brilliant because of the placement of the screws, but geez, you know, like this top one here in this cage.

I had to take that out with a pair of bloody pliers. I'll tell you what I do like how most of these can just slide out like that and the screws can stay in there because they got the little key thing in there and I can just access that wire there and that's the one that's going to the Crt I think. and check it out. I really like this.

This tube going all the way down to the bottom that actually contains the coily cable for the keyboard. I like it so I can't. You know it's not just flapping around in the breeze in there. It can't get like caught on stuff they got in a nice metal tube.

Nice attention to detail. Well, it's not going to come out without a fight. There's a couple of cables on the bottom of this assembly which are supposed to be accessible from that bottom slot you saw, but then they're all cable tied in place down to the bottom of the chassis. So uh, I don't know.

This is absolutely maddening. I'm trying to get this connector out of here. and oh, I did. I finally got it.

I barely fitted. Ah, tight as a nun's nasty. Now, this other cable here, right? This would come out if it wasn't for the bloody cable ties here here and down the bottom. It disconnects from the bottom, but there's a bloody cable tie down there and it goes to the speaker.

Who the hell put the speaker. in the power supply inside the power supply chassis? You couldn't whack it on the i don't know the side of the case over here or something. I'd like the back here. Maybe I don't know why inside the bloody power supply cage, and then why cable tie the damn thing down multiple locations where you can't get the module out.

Ah, cut that stupid mongrel and there it is. Ta-da And we should get access to the entire motherboard now and then. Oh yeah, we can see the power supply now now. We can should be able to inspect that without taking it all out.

But yeah, something's blowing somewhere. A cursory glance over this doesn't show up anything. There's electrolytic caps on here. There's no tagged hands, but all the electrodes are in good nick.

There's a couple way up the back there which you can't see, but I can see and they look. They look all okay. So nothing's gone. kaboom on there.

So it looks like uh, the sparks were much bigger and must have come from the main power supply. And once again, a cursory glance from like way back here doesn't seem to show up anything. All the main electrodes look alright. They got the vents on the top.

Nothing happened there. a couple of big tag tents there, but the actually I got two tag tent fragments out of this thing. Um, so I I don't see anything obviously blown on that border. I don't smell anything either, so I'm still baffled as to where it's coming from.

Don't have to get that board out. There's no burn marks as I can't smell any residual stuff afterwards. Nothing's obviously blowing, but had to be a cap somewhere. And I know everyone wants to see the money shot.

Here it is. Here's the main Pcb and uh yeah, it all looks good. There's no orange tag tents on here. There's uh, you know, a couple of the yellow Jobbies, but uh, they look fine.

We've got five slots. different space in here. Geez, that's a bit. oh it's it's.

just not sure if I can deal with that. Oh anyway, um. socketed ram here. Another dram here.

So I I believe it's supposed to have 128 uh K base memory. although the uh, expanded plus model could have more. I'm not sure. Um, so I'd have to get the part numbers off there, but that's either 64k.

uh for those two banks or it's 128k. I would guess. Well, we don't have to guess because the camcorder has a zoom function and of course they are 64k bits a pop so I'd buy one a bit. That's K bits, so we've got eight of them there.

None of that parity rubbish. Um, so yeah, 64 128? So this one is populated 256 on the board that's not too shabby and that over there that is going to be our famous compact rom, so I might actually uh, rip that out uh and read that in and dump it and it'll be yeah, compact. Now that Ibm rubbish or Phoenix who came later and then all the other uh cloners once, uh, Compact did it everyone realized got away with it legally, Then everyone else went. Yay, we can do that.

No worries. Anyway, I just got all regular glue logic on there. Nothing fancy. 82 37.

I will just scan across there regular glue logic. no worries. Uh, in Amd P8237, that's a Dma controller because you know, none of that static ram rubbish. You've got to figure out the dram.

And there it is. There it is. It's an Amd 8088 Ah, with a Copros unpopulated co-processor socket. Sacrilege.

Anyway, you can upgrade this bad boy to the uh, V20. Oh yeah, there's a clock up in the top corner there 14.31818 megahertz. And if you do get your confuses out and uh, divide that by 4.77 megahertz. I'm sure you'll find that comes out to an even multiple.

Anyway, Um, yeah, is that a that must be a small little Gatorade job I guess. Um, so yeah, there's nothing else fancy on here. Oh no, sorry, there is parody down the bottom. They do have parody.

Oh wow, look at that extra bit of dram. they got the ninth chip, didn't see it. Anyway, there's a lot of space for roms. check that out.

so I don't know, did they have an option for dos in rom? Maybe. Oh, there's very few computers with dos in rom. The Australian Kookaburra done a video on that might have to link it in. That's one of the very few that on the market.

In fact, it was the first one to have dos in rom, and apparently it's quite hard to do. Ah, there's the culprit. Look at it. Wow.

that's at the snot line out of it. Thank you very much. Oh, Tantalum. I guess I have to crank up the old tunnel of mine out in Western Australia and mine some more because that one's Gonski was that it was that the entire bang? Hmm, maybe the real? Maybe the main power supply still works.

So that makes sense with the uh location of the flash, Because that was, you know, pretty much right behind the uh, floppy drive there. So yeah, that adds up. So off the bat. apart from a closer inspection, I need to get out to do that.

Um, the main supply looks like it's okay. I mean, I don't see any. uh, Reefer Madness caps. Maybe inside they field? Maybe inside the mains input block in there might contain some reefer caps as a filter, but that's hermetically sealed.

We can't do anything about that. If you're going to restore this computer and you know, use it for you know quite significant purpose, then you would go in and recap this whole thing. Uh, you know, get all, get rid of all the tag tents. you know, change the electrodes, everything else.

I mean, it's just ancient, All right. Let's have another go, shall we? Let's just plug it back in minus the Crt, minus the video card, minus the floppy controller with the blown tag tent, and uh, we'll just see if we get five volts on the rail using the new Bm786 available shortly. Anyway, let's plug her in. There's a fan, but I think that's directly mains.

that's direct mains. Nothing's going banksy yet. Well, I don't want to put my head right over the right over those electrodes. A bit of a worry gonna land.

Didn't see that. I don't really see any major test points on here, which is kind of annoying. Ta-da 5.085 Thank you very much for playing. So that thing should be at least booting and I assume it's I don't know if that's a heartbeat, lead or whether or not it's just a, you know, a power on lead.

All right. Here we go. Uh, composite output to a monitor there and uh, I'm not sure if you have to like change jumpers on the board or anything to enable composite output, but anyway, let's give it a go. Yeah, that Led on the bottom is still on.

You can't see it. but whoa. Well did something. Yep, yeah, we're getting something.

I see static. there's no text. Ah, that's a one-on-one Wow. But as I said, could just be jumpers because I did read somewhere that maybe you might have to set them.

There is a service manual in quote marks for the Uh 286 version of this. Not, it doesn't. The diagrams don't seem to match up. Uh, for that's the compact.

Uh, portable Two, it's called. this is the portable one. I guess for one of a better word, this is the original one even though it's the plus model. But yeah, I know there's something there, but not no text.

Okay, so I thought maybe it's not pairing up. Uh, because it doesn't have the uh disc controller in it. So I thought I'd uh, plug the disc controller back in after fixing that uh, tantalum cap there. And no, it makes no difference.

I get the same sort of cruddy crap on the uh composite output. I've tried changing a few jumpers on the video card. I'm measuring the Uh 12 volt rail now. so the 12 is, you know, 12 and a half and uh, but of course that's you know.

Probably neither here nor there for like the powering the thing up and our five volt rail is good so a voltage rails are good, but I'm getting no composite output. I still don't know if that's due to the fact that it's not configured to give composite output. Um, I guess the next step is to test the Vga, the Cga output. Sorry, none of that Vga rubbish.

Um, but I don't have like a Cga monitor handy so I can't just plug it in. I'll have to like check for the signals with the scope or something, but you know before that you're probably better off checking like processor clock and activity and stuff like that. So power supply is working the 5 volt rails there, even the 12 volt rails there. So you know in theory if the logic is good, it should boot up.

I think actually looking at these two screws here, I think the motherboard actually might pull out in a cage as a modular thing. If that's the case, then I can get in there and give it a good visual once over. So I'm gonna do that. Get those.

Well, one of them's broken there. We go there we go. Keyboard cable is in the way. I didn't forget to undo it, I just it's just in the way and it's a bit messy.

In fact, that's really messy. but it does come out ta-da All right, There's a complete motherboard money shot. Now we've got some dip switches here. I believe these are like for setting up, uh, the floppy drive settings and stuff like that.

And there's supposed to be another dip switch in here, but which normally sets up the, uh, memory settings and stuff like that. But I've read that recent versions of the bias actually just didn't bother reading those. They just auto detected how much ram is in there. So um, yeah, that's all hunky-dory and well, our supply rails are fine.

So why isn't this processor working or the process it could be working could be the video card? We just don't know yet. So what I think I'll do is, I'll just start, maybe reseat all the socketed uh chips here. And oh, we're probably reading the rom as well. But yeah, I'll just reset them all.

And maybe it was just a, you know, socket problem. And as you can see there, the pins are. well, they're a little bit crusty, aren't they? Um, that's what happens with age. Of course they're nice and shiny where they go into the socket.

but jeez, yeah, they've uh, they have not aged well so I was able to read out this rom. It turns out it's a 64 kbit rom. Even though that my uh, Tl 866 programmer plus two didn't actually support Mos Tech chips, it didn't matter, it's they're just like same pin out, same everything. So unless you're programming them, if you're just reading them, it's not a problem.

Um, so I just uh, set it as a 64 and you can see if you set it to a higher value. If you choose like 512 kbit or something, it then just duplicates the information. it just reads it multiple times. So uh, by doing that, you can just search uh strings through there And I was able to find you know, Copyright Compact.

There it is. Start and the end. Uh, of the rom dump. So that's how I was able to tell that it was a 64 kbit one.

So a two seven? Uh, C64? You just choose that. Anyway, the good part about this is that I can now get the power supply outside the case and just troubleshoot this, Even plug in the cards. No worries. So get easy access to probing.

Brilliant! So I can just power this up on the bench now. And is our lead on? yeah, Outlet is on so that looks like just a power lead. I don't think. I'm not sure if it's a heartbeat lead built by perfectionist telefunken.

Zippity Doodah? Hmm. All right, clock time. It's powered up pin 19 of the 888. Remember that from a long, long time ago in a Galaxy far far away? 4.77 megahertz? Of course it is.

So we have the clock. No wackers. I don't see activity anywhere else on this get in a clock, but it's almost as if it's like held in reset or something. Well, reset is Pin 21.

It's active high. Yep, the processor is held reset. So that's why it's not doing anything. So all that static was just seen on the composite monitor.

That's just. I don't know. It could be like a free running output or something like this. Like there's probably nothing.

No, no, there's absolutely nothing there. It's just picking up noise and crap. So yeah, process is being held in reset. Hmm.

Well, that's actually not a bad fault to have. I'd rather have that and be able to trace and solve a reset problem than to have i don't know activity on the bus and then it's just still not working. So yeah, that's a. You know, it's a fairly easy one to at least start with.

So the next thing I do is actually check that reset line to see if it's a logic high or whether or not it's actually short and high. Because there could be. Who knows. There could be like a tag 10 on there.

that's like a power on, uh, reset high or something. So Pin 40 over here. that's our 5 Volt rail and Pin 21. No, it's a Meg, so it's not a short.

That doesn't necessarily rule out like some voltage dependent, uh, you know, issue or something like that. But really, you're clutching at straws. There, it's It's not a short on the rail to the 5 volt, so there's obviously some logic driving that. but there could be another, uh, you know, shorter T10 somewhere else.

Now, we don't have the schematics for this, but if it's anything like the Ibm Pc, and I have no reason to suspect that it's not because they released the schematics for the Ibm, so no doubt I copied it fairly closely. Uh, the. and of course, the 8088 has a Uh. companionship.

The 82, 82 84 uh clock chip, which is where the reset signal usually comes from in an Ibm Pc design. And I know this because I've done a video on it. I actually published a um, Attendee 1000, which is my original Ibm Pc that I had and I designed a turbo board for that. and I hacked into the ship and that's where it comes from.

So I've got to find that on here somewhere. It's got to be there, I'm sure. Oh, geez, that wasn't Hard 8284 There it is. Of course it's right next to the crystal because it's the clock timer chip.

Um, so the reset, uh. from inside this thing. Here's the data sheet here. it actually comes from.

There's a like a power good, uh, not a reset pin. and it's pin 11 here. So uh, where pin 11 comes from? Don't know, Don't care. So we're just going to measure pin 11.

so I have no doubt that the reset output of this is just the logic drive I going over to here. So there's nothing wrong with that. But pin 11 could be like shorted on the input or something. So let's go ground and 20 Ohms? That's pretty low.

What about positive rail? Ah, 74 Ohms. That's they're both really low values. Let's swap the probes over. it's still 20 Ohms.

Wow, that is really low. With probes in both directions like that, you know it's actually not an active element part Doing that, it's not like a like, you're not just getting like turning on a diode junction or something like that because if we swap the probes over, that's a little uh trick you can use to see if it's like a genuine hard resistance in quote marks um, or whether or not it's just you know you're turning on a logic gate or something some multimeters. back in the old days, it was actually quite common. Very few of them have it these days.

They actually have a low ohms uh button on them which actually sets, uh, the resistance. Uh, test maximum compliance voltage of the resistance range to under like a half a volt. I.e it won't turn on any diodes and stuff like that. So yeah, there's something on Pin 11 there, so that, uh, not reset input.

It's usually like a power Good signal. Here's a, uh, schematic from the Ibm Pc and you can see that it's uh, labeled a power good. So um, that usually comes from the power supply. So the power supply will usually indicate to the processor whether or not right? Like, the power is good.

Um, a logic output. So I think that's what's happening. So it's likely that Pin 11 there goes all the way back to our power supply over there. That'll be my guess now.

Unfortunately, I can't trace that pin visually because there's no track top or bottom and this is a multi-layer board. so I just have to probe it and see. Well, that didn't take long, I just did that off camera. Um, it.

It was the second pin I probed here. There you go. 0.24 Ohms. So um, the second pin over on the Uh power supply? So yeah, but there, there's just the power supply charging up so it does actually go up.

No. 20 Ohms. There you go. That's interesting, but it is a direct own ski short.

Yes, that is a real term Owmski. or at least I'm owning it. There you go like 0.21 Ohms. Okay, from Uh pin 11 of the 8284 to the power supply over here, so it looks like the power supply is actually indicating that there's a fault, so that there could be.

I haven't measured all the rails, it could be like the minus 5 volt rail or something's dead and well, it just stops the rest of it powering up. which is a bit of a bummer, but you know, so that's a properly designed system. I think I'd rather have a bodge so it like, well, at least partially works. Anyway, this video is over 30 minutes long and well, I'm gonna have to get the bloody power supply out of this thing by the looks of it.

And yeah, that's a lot more work so I might leave that to a apart too. But anyway, this was. it. wasn't supposed to be a repair video, it was just supposed to be a uh, tear down and look at the world's first Ibm compatible Pc.

And not only that, it was portable. the Compact portable. absolutely fantastic. And it catapulted Compact to absolute corporate, uh stardom.

The fastest rising startup business in Us history. I don't know who eventually beat them. I'm sure somebody did. But geez.

Anyway, they went from naught to hundreds of millions of dollars um, in their first year. Uh, you know that's like real revenue, not valuation you get these days on startups. So anyway, if you liked the video, please give it a big a thumbs up. As always, discuss down below and over on the Eevblog forum and check out all my alternative channels and I will.

I'm thinking about let me know in the comments down below. thinking about possibly doing uh, you know, the occasional exclusive video for my Um Odyssey uh channel. Like, if I repair this one, I could do like a repair video Working on Odyssey? Let me know what you think about that Anyway, Catch you next time you.