Hi Hot on the heels of the previous video where I uh tore down the Cambridge Z88 computer, we got another one of a similar ilk, the Amstrad notepad NC 100 and it uses the same BBC basic we saw in the Cambridge Z88 apparently and uh, it's a little bit, uh, younger I guess it's uh, 90s, um early '90s vintage there We Go 1992 vintage there, made in Japan instead of made in Scotland and uh, it's you know, similar little battery powered A4 notebook looks like it has a battery backup in there of course and little couple of little flip out feet. this one's actually missing the battery door here, so bummer, but still, it's going to work. It's got a cereal and a parallel port on it DC jack contrast eh and a memory card expansion slot. and the good thing is it doesn't work.

so I thought we'd have a crack at fixing this one. First thing I'm going to do is check the current consumption of the battery to see if there's any standby current at all cuz it does seem to use a soft power switch so no, I can't see it. That's no, that's not 0.1 It's still the same if I lift the probes off there I expect it to draw. at least you know that's like in the order of uh uh, 10 nanoamp so you know you'd expect it to have some sort of standby power consumption.

But it's got zip. Now there's one totally f fasinating aspect of this thing, which I absolutely love. Look at this door down here. You flip that off and Look what you've got.

You've got what looks like the ROM chips. Let's whack it around here so we can see it. there it is. Amstrad UK A2 That looks like it's a masked ROM chip so that you can change the ROM just by lifting the panel and whacking in a new chip.

I Don't think I've seen that on any machine before now. There was one of the screws missing on this thing, so maybe somebody's had a crack at this thing. Only one way to find out. Looks like we have some metal work under here.

Looks like there's a couple of catches along here. I've got to snap off first and here we go: I got it. I think I thought I did. Yep, there we go.

Tada Nakajima I Guess that's a uh I don't know. Is that some sort of date code? production date code? Look at the shielding on this thing. It's actually quite. uh, quite quite substantial.

They shielded the entire keypad backing on that and the main board as well. Neat. It looks like this just lifts out here. the keyboard's connected.

looks like I can probably flip it over like this and lift that off. Tada That's easier. We have the main board predominantly uh, surface mount almost all of it and and we've got the Uh LCD up here, which we didn't see last time on the Z88. So yeah, that's actually, um, fairly modern.

but that's what you'd expect in the differences between the 1987 vintage Z88 and this 1992 vintage NC 100. Now let's have a look and see what we've got here. Yes, we do have a soft, uh, tactile power switch up here, so maybe there's something wrong with the uh, just the power on circuitry. It could be that simple or it could be more complex I Guess we'll find out.

Got our DC input jack up here. There's the Uh battery backup CR 2032 backup battery Got a couple of mod wires going around here. They've uh, hacked in there. There's a little resistor there, plus two mod wires.

So they've done this after. uh, after production. Obviously they decided to make those changes. couldn't be bother to respin the board cheaper just to put a couple of mods on there.

There's our XY L Z80, CPU uh, our main uh LSI uh Asic up here which would handle pretty much uh, everything else. the Um apart from the CPU because we've basically got the big LSI, we've got the memory. There's the ROM socket on the back, there's another device there not sure what that is off hand, and a couple of miscellaneous uh chips over here and another one up there. But apart from that, that's it.

I mean this would be the serial chip up here cuz that goes off to the serial Port Uh, but this puppy would handle all of the system architecture for the Z80. Uh, for a Z80 uh CPU computer and we've got our date code 20th week 92 so it was uh manufactured. would have been manufactured fairly shortly after that and all the date codes uh for the various chips seem to uh, match so would have been manufactured in the weeks or months after that. Um, there's no Crystal it just uses a ceramic resonator there at 12.2 MHz this is a real time uh clock chip of course I you know I don't know the number of hand 8521 but there's the 32 oh, can't see that on the screen.

there's the 32 khz uh watch crystal right there. nice little solder strap on that I like it. Um, pretty old school stuff. a HC o which they didn't populate for some reason.

not sure why and it is all, um, you know, fairly modern surface mount stuff. It's not ancient like we saw in the 1987 vintage Z88. and there's the main chipset d65 034, Gd93 man I reckon you'd have a hard time finding data on that I don't even think I bother Googling it. We just have a quick look at the display board here.

We've obviously got some sort of uh, you know, 8bit parallel interface or something like that and we've got Oki uh brand display controllers. very common, uh for the time and still nowaday as well. These are 52.99 C's so it's got a bunch of 52.99 C's all the way across there until we get to the end where it is an M 5298 A instead of a 5299 C and on the back of the board here, we got a surprising amount of uh, passive stuff around here. Tons of it.

Check it out. They've got that, uh, plastic insulating uh sheet there so it doesn't short out to the shield in there. An absolute buttload of uh resistors and so 23s on here as well. Tons of them.

There's our ROM and uh. there's a few more stuff up there near the parallel port as you'd expect, couple near the cereal, and whole bunch more. uh, looks like a series resistors on the expansion header there. Now, before we start to go feral on this thing with the scope, let's check out some Basics.

Here's our uh, battery input here. It looks like it's got these two tracers going directly all the way under there, all the way under there, nowhere else. Directly over to the DC power jack, so it looks like it's just in parallel with the DC power jack there. Now, this soft button obviously has to do with something around here soft start power switch.

but let's have a zoom up in here and there's something that immediately sticks out: F 301 0.8 amps fuse. Ha! Can it be that easy? Let's get the meter out and measure it. Let's have a go here. The meter works as both a convenient uh prop for the item on video and ah man, it's blowing.

Ah, so so much for the repair video folks. Sorry. Thought it'd be more interesting than that. Probably not.

But of course, the thing is, why did it Blow I Don't know. Let's um, measure the other side of it and ground, shall we? So we'll get our ground here. Let's assume that this around here is ground. I'm pretty sure the big plane is always ground, so if we measure this side of it, no, No.25.

Meg That's all fine and dandy. Don't mind that at all. And it looks like they, uh, specked into the design common mode choke there. but they've just decided to short it out.

There's the ground, so it would have gone from the DC input jack through to the ground like that. but it doesn't. and uh, of course, a DC input jack through to those filter caps there. but it doesn't and we'll just measure across that filter cap there to make sure it's not shorted.

and no, it's not 46. K and you'd expect it to rise as the uh capacitors charge up. So that's all working. Hunky dory.

So um, I'm going to presume that the Uh power rails I'm not sure if there's another voltage regulator on here. There certainly could be. um, that there looks like it could be a voltage regulator. so maybe they have a 5V regulator on this thing.

Although if you're powering it from uh, 6vt batteries, the four uh Aa's in series, that's um, 6vs, uh, nominal. Um, but that's going to drop fairly drastically. So a 5vt regulator, even a low Dropout one isn't going to regulate uh for very long over that full battery discharge curve. So what I'll do is I'll just power this thing from a 6vt bench.

Supply And uh, let's give it a go. So 6 volts, switch it on and soft power switch. It's a drawing any current? Oh yep, there we go. Yep, it's on.

Ah man, too easy. Where's he? Yeah, there we go. Lithium battery is low. Please switch off and replace battery.

We have a winner folks. All it was was a fuse. That's actually very disappointing cuz I was hoping that we' uh, hopefully we' get something more exciting than that. but no.

Well, I didn't have a direct surface mount replacement so I just put little axial one in there. No problem, it should fit nicely against that metal shield. I think we've got the insulator there? Not a problem. So I'm going to put this sucker back together and we'll Power It Up And here we go.

We can see the standby: Uh current consumption here about 72 micro amps or thereabouts. So let's switch this sucker on Bloody default AC Pain in the ass so let's see about 60 milliamp. So very similar to the draw of the Z88. Let's have a quick squee.

is here at the main clock and should be 12. There we go. 12363 MHz that's the um, that's of course not a crystal that's a ceramic resonator. And let's have a look at the main oscillator as well which is pin one of the 44 pin Plcc package and it is continuously I Want to say it? Yes, it is continuously running.

Although this thing uh, isn't at in at its application mode yet, it's just giving that uh display. There you go, it just switched off. so uh, but let's what was that running at? let me switch it back on. There you go, it's running at 6.18 MHz so that's pretty quick for a Z80 processor.

and because the back case is not on this thing I need to still access and probe the circuitry. uh I can't put the coin cell in back which is really annoying. So I've hooked up another Supply over here. so let's power it on and we should get no Lithium battery.

ah helps. if I turn the load switch on, let's give that a go again. There we go Tada we're up. We're in the main screen.

Brilliant! Works A treat. and interestingly, the current drawer is now, uh, jumping around a bit. but it's you know, going anywhere from uh 40 odd milliamps up to 50 so that possibly could indicate that the uh clock is uh, skipping again to save cycles and save power. So let's probe that again and see what we get.

and bingo there it is. Let's single shot capture that, see what we get. We've got a couple of bursts hu large bursts here of a 2 milliseconds, six just over 6 milliseconds each with a dead time of uh, almost 4 milliseconds between them. And then we've got a shorter little burst here here, which that's about 200 micros per Division 200, 400, 600.

You know, 700 odd microsc burst there. There you go. So it looks like it has a couple of these shorter bursts with a couple of longer bursts. and uh, it's just waiting for the Uh keypad.

I'm assuming it's just waiting for a key. So let's press a key and yeah, we can see it. insert. Ah, there we go.

It just not only did it insert a couple of more I'm not sure what I'm actually running here I have to flip my screen over I'm not doing anything actually. Um, enter doesn't do anything at the main screen, so let's go into the word processor. press the yellow and red. so there we go.

It does seem to jump around a bit between. uh, actually, between having none of those longer bursts. See there, it is very interesting. So let me call up the word processor.

There we go. Bang, You saw it. Uh, just go full speed there and we're now inside. No, we're not inside the word processor.

It's weird, so you can see how this main Uh system ASC here is always running by that uh 12 MHz ceramic resonator and you know it's they intern. I Guess it can shut down its internal uh Parts as well when it's not doing anything to save power, but the oscillator always running there and only supplies the clock through to the CPU uh when it needs to. So this will handle the Uh keyboard as well so that it's uh, sitting there waiting for the key presses to uh, turn the thing on Supply Power interrupt the CPU boot it up and uh, start it, run it again and action those keys and that's how they save power on these types of systems. And this is the coolest key ever.

Secret Menu: Let's see what's in there. Let's press this sucker and and see what we get here we go. Enter password: Oh, let's try I don't know 000000 what the Sean was here. This is one heck of a big calculator display.

Woo! Love it. No scientific functions though. Bummer. Unfortunately, there seem to be a couple of stuck keys on this thing.

The shift and this one up here seem to, uh, get stuck. I've tried to sort of clear them, but H it doesn't seem to work. If anyone's got any good ideas for that, let me know. And it's really not obvious how to get into the BBC basic either because looks like you can't scroll this main menu.

It's only got the word processor, calculator, and diary address book which you use you know, function sort of. you know word that'll take you into the word processor to start a new document and this takes you into the calculator and you know, um, press stop takes you back to the main menu. Well, it's function B Apparently there it is and there's RT Russell Again, and we got our little basic program there, looping through printing. Ey.

Yes, it has to scroll the whole screen I know I haven't put the semicolon at the end of it. Whatever, let's run it. It does seem to be substantially quicker than the Uh Z88. No surprises.

It's running exactly the same basic interpreter on the Uh Z80, but it's running at, uh, like a double the clock rate. So let's uh, probe this clock again and see what we get. Took it in here and pin one on our clock. There you go.

It is fully fully continuous. So let's uh, put this down here and we are getting more. Uh, just over 5 volts there. 1, 2, 3, 4, five.

There we go. and if I adjust the uh voltage on my Supply that doesn't go up so that's clearly being regulated. Now here's how main clock and it's just over 5 volts there. and what I'm going to do is I'm going to drop my Supply voltage here and see where that thing drops out.

Ah no, it looks like there you go. it's regulated. It's regulated folks. It's not a it's not a 5volt linear regulator so it's working all the way down.

Wow, There we go. drops out at about 3.3 volts. That's very impressive. And with everything Tech there's an Enthusiast group for everything I present to you the CPC Wiki., Euu, a surgical Guide to the Amstrad NC Here it is they've got some uh cool looking Asy diagrams here which uh show which tell you all the details.

There it is 6 MHz yeah we measured that 64 uh K internal memory 15K System 11k upper 32k lower It's got a Pcmc slot which allows you to expand to 1 Meg uh maximum. It's got a 480x 32 pixel display usually 8X 80 There you go 40 to 60 milliamps which is what we what, what we measured and uh, how to get the firmware, number, memory cards, how to open it already done that? what's inside they've labeled all the chips there we go. there's the Uh 6 MHz Z80. There's the Upd 65034 Uh custom chip.

they call it customer chip but it's just a custom Asic and you know a bunch of miscellaneous other stuff. We got the Uh Uart and the Rs232 driver and the real time clock and eh, and interestingly down here this is what: I like the simplified block diagram and as I mentioned before, IC 302 here is the main Asic and it runs continuously on the 12.2 MHz ceramic resonator there and everything looks into it. I Mean, here's Ic31 up here. Here's just CPU and it's hardly.

You know, according to this block diagram, it's hardly doing anything at all. and uh, and everything runs off that. So you got the LCD controllers built in there. There we go directly off it the keyboard Matrix of course, so it knows, um, when you've actually pressed a key so it can you know, start up the clock and interrupt the CPU and all that sort of jazz.

and uh, then we've got our uh, real time clock. Pcmc is all hooked in there, or your memory address and all that stuff is all hooked into that system As6 so the thing man wouldn't be able to do a damn thing without that. A And let's scroll down here. We got our power supply block diagram.

We can probably zoom into that a bit more. Here it is. Um, yeah, there it is. 6 Vols Dcn battery directly connected across it.

there's the fuse, that blue little pan in the ass, and uh, plus 6 Vols and looks like there's plus 5 Vol voltage regulator as as well 5 Vols BK there, which is the backup for the buffer Ram So the SRAM SRAM doesn't need to be refreshed it. You know it only takes microamps or Nano amps to uh to actually retain that information. So as soon as you stop the clock and you've as long as you got that power on those srams, it will, um, retain the data in there for you. So you got minus 15 Volts for the LCD display.

Ah, couple of other things: 4.2 2.3 3.2 Ah man, this thing's got everything. Here we go: The microprocessor ah, the customer chip custom chip I Love it! It's got it. has multiple functions. clock generator for CPU and U uh, the Pia adapter for the printer LCD screen, keyboard, memory management Pcmc sound generator of course.

forgot about that man. Whole ton of stuff. firmware static Random Access Memory Ah, this Wiki's got everything I Love it and good on your hands Jer Bing if I'm pronouncing that correctly from Doozledorf in Germany Fantastic and contributors Mcde and Niler as well. Awesome! Thanks for sharing the information.

It's brilliant. So there you go. There's a little look at yet another uh, vintage notebook computer. Hope you liked it.

Sorry about the repair. As boring as bat poo. Ah, you can't win all the time. But anyway, if you want to discuss it, jump on over to the EV blog forum and if you like, please give it a big thumbs up.

Catch you next time.