I love it when Noel's like 'Come on Sinclair' when it comes to the cost-cutting measures Sinclair took to penny pinch and undercut their competitors to build their product.
@@NoelsRetroLab Be careful using the square pin headers in IC sockets , they can stretch the contacts in the IC socket and then when you put the original chip back it doesn't make proper contact. I prefer to use the round turned pin headers for this sort of adaptor, like the socket strips you had but pins on both sides. They will also fit in turned pin sockets which the square pins wont.
@@jameshearne891 Good point. It was a tight fit in the sockets and the ROMs felt that they went in really easy after that, so they definitely stretched some.
@@NoelsRetroLab Stripboard would also save on soldering, but I don't know if they make it with vias. It was single-sided when I last used it. Anyway, using the same holes was cool.
I know im asking randomly but does anybody know of a tool to log back into an Instagram account..? I was dumb lost the password. I appreciate any help you can offer me!
@Deangelo Ty i really appreciate your reply. I found the site on google and Im in the hacking process now. I see it takes quite some time so I will reply here later with my results.
Hey Noel, Im an engineering student over in America. Love your channel and your videos make me want to get into this hobby. Keep up the good work, i always look forward to your videos
Hey Cameron, I agree with Noel, but be prepared to spend a lot of time sourcing your retro stuff, and also to have to pay good money for it. For example, I spent the better part of 2019 finding a Commodore 128D, a monitor, printer, RAM expansion unit, cables, diskettes, extra disk drive, and other paraphernalia, which ended up costing me around a thousand dollars (USD) in total. Also be aware that there's always a risk that what you buy (on e.g. ebay) may not always be working properly; so far I have been lucky in that respect: all my retro gear i've bought over the last 9 to 10 years has been in good working order.
@@BertGrink Sure, but that's if you want some really specific/expensive stuff. There's plenty of retro stuff that's really cheap. Since he's looking to get into it and probably repair things, if things don't work or aren't tested, that's even better 😃 People give it out some stuff for free or very inexpensively because there's so much of it (for example, ZX Spectrums here in Spain), and that's perfect to learn with.
Hi Noel, Thanks very much for releasing these excellent videos, I have learned so much from you. I have now just completed my first ever computer repair, RAM chips on a 48k Spectrum, I would not have attempted it without first being shown so much by you. Keep up the great work :)
I recently fixed an Apple II+ clone that had all the memory soldered in, I used the thermocouple on my multimeter with a bit of heatsink grease. I let all the chips warm up and noted all the temperatures and found that 1 of the chips was COLDER than all the rest ~8c. Replace the chip & fixed it. It's not always the hot chip that's faulty. Also: the ROM socket is now potentially faulty, you have stretched the leaf springs by inserting the machine pin socket pins. I recommend you replace them.
@@NoelsRetroLab There was nothing obvious using the scope. I believe it may have had faulty CAS/RAS inputs or open VCC to some internal parts making it not do anything. Just to clarify they were 4116 DRAMs all same make & date code, once warmed up they all were 36 to 38c except for the faulty one at around 29c.
Tip about removing the ICS without a desolider. Cut the IC pins and remove. Put lots of flux on the remaining legs and use pincers and the iron to remove one leg at a time. After this again flux and this time heat the hole and use a cocktail stick to rotate the hole open. Remove the iron and it stay open ready for the socket with no damage or stress :)
Personally, I think it's fascinating that the green and red power up hash pattern was almost identical between both boards! Guess I'm just used to expecting random garbage out of memory at first ... presuming it is sourced from RAM, I'm only 10 minutes in so far but loving your approach Noel! Edit: That same display using Q-Emulator is notably different! Must say, I love these kinds of puzzles (so to speak!)... Possibly relevant to someone, you should note that the Interrupt control on the 68008 is different too, just two pins and the ordering might be different on the legs ... IANAE Ymmv etc 😀
It is interesting the cost cutting things Sinclair did with the QL like the Microdrive connectors, yet they included a very expensive expansion port connector when it should have just been a edge connector, and the socketed chips when they could have just been soldiered in.
I remember my father having one of these when I was young. It was mostly something curious to him though as he had Sparcststions in the same shed as the ql along with an xt!
A fascinating computer. Unbeatable value when it was released. If I wasn't still programming for CP/M at the time then I would have bought one. Pity about the microdrive system. Those sockets resemble thew ill fated SIPs...
Great video Neil :-) I'm just getting a QL back to life and used your little circuit for the Minerva ROM, which worked first time! However, with the M27C512 and the 7404 in sockets I can't get the keyboard back in place, as the new ROM board in the existing socket is too tall. How did you get round this? Or did you only use the Minerva ROM for testing, then take it out and put the original ROMs back in before putting the keyboard back? I want to be able to reprogram the M27C512 in future if there's a Minerva update, or I fancy another ROM, so soldering it onto the PCB board would make the M27C512 unprogrammable, as the wiring from the header pins to the M27C512 will be for an original Sinclair ROM. I'm considering doing a new version of your board, with the M27C512 and the 7404 solder directly to the board, but adding some jumpers so that the header pins either go straight through to the pins on the M27C512 for use when programming it, or switch the pin connections around to use the wiring as in your diagram. I reckon I'll only need three two position jumpers to achieve this, or do you have any other suggestions?
You can make simple inverter using 1 transistor and 2 resistors. Or, even simpler, 1 MOSFET and 1 resistor. That would easily fit inside the chip socket or on top of the chip (for more permanent mounting).
The color of the screen that ends up with (green or white) when booted - might be an indication of the lower or upper RAM failure you think? this could be a starting point to investigate - Great job btw :-)
Interesting! It didn't occur to me. I'd be surprised if the technical manual didn't mention that when they explicitly called out white and green, but who knows! If I had more chips socketed I could try running some experiments 😃
Do you have a link to any diagrams for the wiring and which pins are not connected through the PCB? Wanting to build this up but a bit tricky to see exactly which pins are not soldered or connected. Thanks.
ICL produced a rather rare variant of the QL called the "One Per Desk" which had a built-in telephone as well as a voice-capable V.23 modem which allowed it to answer phone calls and provide interactive menus to callers with its onboard speech synthesizer. It was developed in cooperation with BT and was marketed by them as the Merlin Tonto and by Telecom Australia as the Computerphone.
Another fine video from Noel just on time at the end of a terrible day at work. I wonder if we will have a #DECember next month :-) That would be a challenge too, but nothing that Noel could not solve ;-)
Does it matter if you would use an EEPROM or EPROM? The one you have in this video seems not to be available anymore (at least I didn't find a reasonable priced one). And newer EEPROMs seem to be only available in 8DIP version. What do you recommend?
It shouldn't matter if they have similar pinouts. I don't usually use EEPROMs, so I don't remember off the top of my head, but if they do, that'd be fine. However, 27CXXX EPROMs should be very easily available everywhere for pretty cheap. It doesn't matter too much if they're 256 or 512 as long as they're big enough (you can duplicate the data inside if you want).
My mum was at a jumble sale, at the village hall. Back in the mid 90s. She knew I was keen on computers. So got me a QL. Was boxed. had some microdrives. It did work. But the microdrives were a bit unreliable. Hey it is a sinclair. Think I just put it in storage. As was more interested in 8 bit computers
Interesting I still have mine but have never touch it for some time now. And as I packed the boxes to move house some 14 years ago. Wow has it been that long. Sorry about that. I might try and find it . Looking to see what you make out of them. I was always working on spreadsheets and info for my job.
Good video. I'm sure you know the 'laser' thermometer is just an IR thermometer with a laser pointer. I hear 'laser thermometer' very often in UA-cam video's. Not sure how many people think the laser actually measures the temperature.
Hey Noel, when you built that ROM adapter on perfboard, i was thinking, wouldn't it have been possible to place the Inverter IC inside the footprint of the ROM? If so, the board could probably have been made much smaller. Perhaps that might be worth considering, should you decide to install the Minerva ROM permanently?
For sure! That's the smallest size board I had around, but if I make one from scratch (which could be interesting) I can do that, or even use an SMD inverter (or a transistor) and put it under the EPROM but still on the top side.
While you're in there, can you expand the data bus past 8-bits, increase the color palette beyond 8, and maybe bugfix the Microdrives and add rudimentary sound? The QL is just so close to greatness.. it just needs a few tweaks.
Excess long undamped CS, RAS and CAS lines in dram chips causes this types of ram burning. That's the why some computers put mild resistors over CS to prevent ringing
Really?? I often wondered what makes DRAM so fragile. When you mean undamped are you referring to ringing around the top of the raising edge? Why would it cause failure, because it triggers transistors inside multiple times as the signal oscillates? Fascinating.
@@NoelsRetroLab Precisely. The longer lines tend to develop inductance and this, combined with high frequencies can cause undershoots and overshoots that eventually burn the input transistors or make the part collide with some other device in the bus. This is a pretty know issue and there are lots of possible mitigations. There was some extra info in old National instruments Databooks. Also, this explains the "per board profiles" needed for the FPGA Memory controller IP's. (Compensate delays and timings mostly)
Great! I wanted one when I was a child, luckly my parents didn't buy one for me :o) A little trivia: It was Linus Torvalds (creator of Linux) first computer.
@@NoelsRetroLab Lol, I could get one now and be the SECOND creator of Linux, whatever that means ;oP Those machines have a reputation of being unreliable, not only because the microdrive, also the firmware was plagued by bugs, and you have seen the construction quality. Apparently they were rushed to the market in an early state. Good job, as entertaining as the 8bit guy, keep on it.
@@ernestuz Like everything Sinclair did, rushed, full of bugs, crap quality, over promised, under delivered and unreliable. It's a miracle any of them survived :) I saw one of the first in the UK at a local computer club (I also saw one of the first Mac machines in the UK at the same club)
The QL was available in so many shops here in the UK in the eighties, but until this day I've never known anyone that actually bought one. I think they were trying to be a serious business machine but they just didn't cut it. They weren't cheap enough for the home user as the Spectrums were (and there were pretty much no games made for them) so they didn't really appeal to either market. The QL was a costly exercise for Sinclair and they never really recovered from the losses.
@Apple yeah Sinclair really didn't want the QL to go along the gaming route. Trouble was, anyone looking for a "business machine" overlooked the QL too. It didn't look professional enough and it still had a similar keyboard to the dodgy Spectrum + one. The decision to go with Microdrives instead of floppy disks was arguably a poor decision too.
@@bionicgeekgrrl It probably would have been a popular feature, but unfortunately that would have meant sticking with the Z80. Adding a Z80 along with the 68008 to the QL would have pushed up the cost, and as you can see, this is a very cost-conscious product!
@Apple You are right, of course. I did work on a z8000 system once - part of a flight simulator - but that was the only application I came across for it. Sinclair would almost certainly have ruled out anything 16-bit on cost grounds. Zilog are still around, and still selling Z80s, amazingly!
This belongs to a time period when breaking compatibility was not as tremedous as today. The same year, Apple shipped Lisa and Macintosh with zero compatibility with the Apple ][ as well.
On my IBM 5150 I tested the 4164 ICS by piggy backing a good one on top one by one. It helped me find a bad one stopping the pc from booting, it might also work here with ql memory issues
I used to have one and upgraded it to 896k of RAM and a Minerva ROM. It’s a pity Alan Sugar dropped it when he bought Sinclair Research. I suppose he found it too difficult to reengineer to add a proper disk drive and keyboard.
I wondered ... What’s the blue tape for? Rewind a bit a of couple of times ... oh, I see ... antigravity. 🙂 Question ... Do you know why Sinclair did not use a power switch? It seems like an odd thing to cost reduce.
Haha, I see you figured it out. It can come in really handy some times! The switch... mostly to save a few pennies I suppose. Someone mentioned that in the UK every wall plug needs to have a switch and that was the reason, but it seems a bit of a stretch.
Noel, after your video I decided to buy one QL, Spanish version Issue5 ooooooh not the last :) that my hands over it right now, ready to open it. I have the white Screen, so I guess it is a RAM chip. :) so double thank you... just... Where is the scheme to built a minerva board?
Nice!! Yes, that looks like it's a RAM chip, so it should be pretty easy. No scheme, just follow the graphic I showed in the video. Or send me a message and I can send you close up pictures if you want. It's just 3 pins that are different, so it should be pretty easy to make.
10 cents investment in better connectors would have caused Sinclair to go bankrupt even faster... :D Nice repairs Noel! Looking forward to more #QLvember content, and maybe even other 68k based machines on the long run... :)
Sir Clive should just have refrained from making his C5 electric tricycle - that disaster was a major cause of his comapny's downfall; at least that's what i think.
@@BertGrink The C5 and QL, which I remember being described in the computer press at the time as a "fiasco" both helped to contribute to the demise of Sinclair Research. It was reported that Sugar got Sinclair Research for a fraction of its actual value.
@@captaincorleone7088 Yes, with _both_ the C5 _and_ the QL, it spelled doom for Sinclair, but i wonder if it hadn't been for the C5, if he could have kept going long enough to make the QL moderately successful. And yeah, Alan Sugar got the company for peanuts, I think he paid around 5 million £ for the whole deal, and there was unsold stock in the warehouses at least worth that amount, from what i have heard.
@@BertGrink That's correct, £5m and the company was valued around at least £15m. IIRC it was reported at the time that Sugar essentially got that unsold stock at £1 each! I agree with you about the C5: that thing was slated in the press, it was a public relations disaster! At the time I was a kid but I still remember how savage the media coverage was.
Do you know that QL stands for Quantum Leap? Sir Clive tried to market this as a 32 bit computer (leaping from 8 bit straight to 32 bit; he actually appeared in the TV adverts jumping over a pile of computers) How did he arrive at 32 bit? Perhaps by adding 24 address lines and 8 data lines?
Yeah, I've seen that commercial. Hilarious! Maybe at first they were going to put a 68K CPU. Not sure. I'll get into that a bit more in the next video.
No, he arrived at 32 with what really matters: the CPU registers (all 32bits, including the program counter, even though the physical addressing could only offer 20 lines). How IBM arrived at 16 bits for the 8088 is a real mystery, however. The bus was 8 bits and it could only address pages of 64KB at a time just like a Z80... Or maybe the Z80 was 16 bits all along and the Zilog marketing department was incompetent?
Those push in wire connectors were common in audio during the 90s for cost saving. Terrible to work with. One of the reasons I gave up audio repairs. You could only disconnect a few times before the connector broke or the wire end unraveled. I have shouted many curse words at them over the years!
I'm wondering if it's possible to change that so hot 7805 regulator with a cooler modern replacement. It's just that I don't like things running so hot if you've got more (sometimes a bit of expensive) options.
I was thinking that too. I once tried to make a PCB by the UV-resist method. I didn't have a UV light, so I used sunlight. I expected not to get enough UV light, so I waited longer than I thought. The PCB was over-exposed.
@@xXTheoLinuxXx Funny to see that 40 years later, the big tech companies are trying to push for the same areas that Sinclair foresaw beyond home computers himself : the car, the watch, the TV.
@@chirchir8126 true. Sir Clive had a lot of good ideas and was a visionair back in the day. He spend a fortune because he thought electric vehicles were the future. Besides electric cars we now have a lot of e-bikes in The Netherlands.
@@PJBonoVox I hadn't thought of that, but it would be a good idea! Although I'm more concerned about the microdrive connectors than the LED ones. I might try something on my QL.
Interesting. No I left them flapping in the wind. Do they really cause noise on the one gate I connected? More than if they were switching following some other logic? When I make a more permanent board I'll make sure they're grounded.
@@NoelsRetroLab it's probably not a issue but it's good practice I've had issues that had me stumped for ages because I used to leave them floating but I talking more high speed things another idea is to tie them all together as one big gate
Was this machine compatible with the zx spectrum software or not at all? I am glad you were able to figure which ram chips were causing the issue. I have more than once had to keep swapping ram until I guessed right. I know there are Arduino Ram testers for the 4116 and 4164 so I should probably make them.
Not at all! Sinclair aimed this machine at a completely different market. I'll get into more details next video. But I'm sure that was part of the reason it was a total flop. RAM testers are useful, but usually you need to remove the RAM from the board, so it wouldn't have helped too much avoiding the desoldering. And there were 16 ICs! Yikes! 😃
@@NoelsRetroLab After the Amstrad takeover of Sinclair's IP, a consortium was formed that obtained the rights to the QL IP, this resulted in some moderately successful machines such as one called Thor, and another called OPD (One Per Desk) which had a built-in phone as well as a modem, thus requiring two phone lines. The main reason i remember that consortium was because the official danish Sinclair distributor, Dansoft, was one of its members, and the magazines here in DK were quite excited over that. ;)
@@NoelsRetroLab Here's an article about the OPD en.wikipedia.org/wiki/One_Per_Desk and there's a _little_ information about the Thor and other clones here en.wikipedia.org/wiki/Sinclair_QL#Clones
Those microdrive slots would house an SD card reader rather nicely. Just need to replace the 68008 with the better version and it'd be a decent machine.
Weird they placed that microcontroller at the border of the board. We usually avoid that like heck as restricts the pathways we have available for the tracks.
Yes, the whole layout is a bit weird, even with the CPU off to the side like that. But at least that's next to the expansion bus, so that kind of makes sense. The board is also super crammed, so they were working with some big constraints (maybe from design first).
Great video! Love it. Glad you joined the #QLvember. Here's my QLvember contribution: ua-cam.com/video/cxs6d108Mnw/v-deo.html In this video I talk about the Sinclair QL Service Manual, which is much more than just a pure Service Manual as it also contains at least part of the QL's Engineering Specification. I also show some ultra-rare original still uncut QL PCBs and talk about details. QL forever! Cheers and stay healthy!
Nice! I just watched it. That service manual was great! I definitely referenced it a lot in my research for this video, but only the digital format unfortunately (I"m a sucker for a good paper book!). Thanks for sharing it! Subbed too 😃
Noel, What I usually use is this kind of vero board: ebay.us/1XN1eu this way you don't have to solder all the traces. But a very good idea to solder the pin headers in the same holes...
Right! That makes sense. I guess you'd need two different ones, one of each half of the EPROM, right? I should have a few of those in hand. Thanks for the tip.
Wow the ol' 68008. That means the QL had to make 4 accesses just to read/write a 32 bit value. Ouch! But nonetheless.... still a more powerful processor than the older 8 bits and I'd put my money on the 68008 over and equivalent 8088 or 8086 any day at even twice the clock.
@@NoelsRetroLab Motorola aimed the 68008 at manufacturers who wanted to save a few pennies, because it needed fewer lines and thus motherboards could be smaller and cheaper to design much like the 8bit motherboards of the time. They were just imitating what Intel did by introducing the 8088 time after the 8086 was released, for the same reasons. In the end, it became more expensive for Motorola to manufacture the 68008 than the 68000 (lower economies of scale) so they stopped producing it quickly.
Who signed off on all those connectors, they are the weirdest things I’ve ever seen in my work in electronics especially that case one with the loose wires, like you say imagine the savings in time in production if it were just a regular push fit connector! Who even made that kind of connector?! Never seen one before. Those Microdrive wires, push and pray I call them. The sad thing about the QL is there was a saleable, value for money winning machine buried in a pile of junk, such a missed opportunity.
I would guess the reason that Sinclair computers originally didn't have power switches is that in the UK, all wall outlets are forced to be switched by law. So you were supposed to just turn them on/off at the wall.
Sir Clive was just a cheapskate. :) Other UK contemporary computers had power switches. His entire business strategy was to cut corners in order to cut costs wherever possible. There's another video Noel did which showed that Sinclair bought up faulty RAM because the Spectrum wouldn't even need the full capacity anyway. :D
Oh wow! I had no idea, but that would certainly explain it a bit better. Are the switches next to the outlets, or are they like the light switch as you enter a door?
Unfortunately that's not true, sockets aren't 'forced to be switched by law' at all. As Corleone says, the reason was probably that Clive Sinclair was just too cheap to fit switches or buy full spec components, he had long history with buying factory reject parts for his products and it wasn't limited to the computers.
@@M0UAW_IO83 Sorry, my mistake. A better way of phrasing it may have been "nearly always have a switch". I agree he was a cheapskate, even if this was part of his reasoning, it was a thin excuse at best!
I know this is a but of a long shot, but can anyone help me with a weird zx spectrum problem? My dad gave me a spectrum (the very first version) that was in pretty bad condition. I replaced the capacitors and the keyboard membrane circuit thing, and tweaked some variable resistors to fix the colours. Everything works ok now, except that if I try to type a basic program in, after a while the screen corrupts weirdly, then it crashes. It kinda feels like the basic program is starting to overwrite video ram or something. Is this a known thing, and does anyone know how to remedy it? Edit: I only have a multimeter, not an oscilloscope, sadly, and the screen corruption is pretty hard to describe. The characters start to deteriorate, and the corruption even changes a bit when I keep typing, then it tends to lock up and crash
Hmm... I would suspect bad RAM. If you have a way to load the ROM from ZX Diagnostics, it can pinpoint it right away. Since your Spectrum is working, I think they even have a TAP version of the test. Stop by the Discord server and bring this up, that way it's easier to post pictures and discuss that. Good luck!
It might be a ram chip failing as it warms up. See if one chip gets hotter, like Noel was doing. Otherwise, try using freeze spray on each chip and see if it lasts longer before crashing. Don't give up :)
Thank you for the video, Noel:) And me again, hehe: Are you sure you want to leave the unused inputs on the 74HC(U)04 floating? Admittedly, I can't really see that on the video, but if I'm right, then in contrast to the 74xx or 74LSxx, it can give a nice -function- noise generator:) Also 74HCU devices do not match 74HCT or 74(LS)xx TTL-levels which match M27xxx style EPROMs. See electronics.stackexchange.com/questions/384672/74hc-hct-what-to-do-with-unused-inputs-and-why or your 74HC(T) datasheet for a deeper dive. And Nexperia/Phillips HCT User Guide, page 30 - 7.4 Termination of unused inputs and Table 11 on page 40. But that is nothing against the noble deed of reviving these wonderful machines. Great work!
sinclair were all about building down to a price, which is why you found connections you weren't familiar with, they would have used the cheapest parts they could find
Nice video. The hardware of the QL never was really good, the magic was in the very innovative operating system. And the case design IMHO :-) Minerva writes one 32-bit word in 16kB increments and reads it back to see how far the RAM goes. If that happens to be one of the failing addresses then the RAM is just cut short as distinguishing between "failing RAM" and "no RAM" is quite difficult. Especially with Minerva, which is so packed full of features that it almost has no single byte to spare in its 48KB area.
Right. Especially after they ironed out some bugs from what I read! That makes sense about having a hard time detecting the difference. It's curious that it does once in every 10-15 times though.
@@NoelsRetroLab Yes, can't quite explain that, the data it writes in that phase is constant and not randomized like the main RAM-test (actually it's just the address, i.e. $0003000 in your case). Maybe the bits are flaky and occasionally work.
I love it when Noel's like 'Come on Sinclair' when it comes to the cost-cutting measures Sinclair took to penny pinch and undercut their competitors to build their product.
Lovely to see both QL's working again =D
Thanks! Yes, glad it was an easy fix for once. Nice warm up to a new-to-me system 😃
Those pin headers in the same holes like that was a brilliant idea.
Yeah, it saved me so much uncomfortable soldering trying to bridge 28 adjacent sets of pins!
@@NoelsRetroLab Be careful using the square pin headers in IC sockets , they can stretch the contacts in the IC socket and then when you put the original chip back it doesn't make proper contact. I prefer to use the round turned pin headers for this sort of adaptor, like the socket strips you had but pins on both sides. They will also fit in turned pin sockets which the square pins wont.
@@jameshearne891 Good point. It was a tight fit in the sockets and the ROMs felt that they went in really easy after that, so they definitely stretched some.
@@NoelsRetroLab Stripboard would also save on soldering, but I don't know if they make it with vias. It was single-sided when I last used it. Anyway, using the same holes was cool.
That was wonderful to see: just like seeing a reliable doctor operating on a patient we care about!
I know im asking randomly but does anybody know of a tool to log back into an Instagram account..?
I was dumb lost the password. I appreciate any help you can offer me!
@Brendan Reuben Instablaster =)
@Deangelo Ty i really appreciate your reply. I found the site on google and Im in the hacking process now.
I see it takes quite some time so I will reply here later with my results.
@Deangelo Ty It did the trick and I now got access to my account again. Im so happy:D
Thank you so much you saved my ass !
@Brendan Reuben You are welcome :D
Oh how I love these computers. Had one when it was first released in the UK. Even today, it still looks a beauty.
Noel, you never cease to amaze me
Hey Noel, Im an engineering student over in America. Love your channel and your videos make me want to get into this hobby. Keep up the good work, i always look forward to your videos
Thanks! I'm really happy to hear that. Don't hesitate and get started. It's really fun and rewarding!
Hey Cameron, I agree with Noel, but be prepared to spend a lot of time sourcing your retro stuff, and also to have to pay good money for it.
For example, I spent the better part of 2019 finding a Commodore 128D, a monitor, printer, RAM expansion unit, cables, diskettes, extra disk drive, and other paraphernalia, which ended up costing me around a thousand dollars (USD) in total.
Also be aware that there's always a risk that what you buy (on e.g. ebay) may not always be working properly; so far I have been lucky in that respect: all my retro gear i've bought over the last 9 to 10 years has been in good working order.
@@BertGrink Sure, but that's if you want some really specific/expensive stuff. There's plenty of retro stuff that's really cheap. Since he's looking to get into it and probably repair things, if things don't work or aren't tested, that's even better 😃 People give it out some stuff for free or very inexpensively because there's so much of it (for example, ZX Spectrums here in Spain), and that's perfect to learn with.
I can't wait until we get to Marchimedes. All march, all Acorn Archimedes.
Ooohhh, I'd be down for that! Only problem is... I need to get an Archimedes first! 😳
Thanks Noel. Just got my first QL in so I'll be servicing it, luckily it boots out of the box
Wow. I have watched a LOT of videos on these old microcomputers, and I have never heard of this computer AT ALL!
It was a bit obscure and didn't make a splash with the 8-bit home computer crowd. At the time I only vaguely heard of it to be honest.
Hi Noel, Thanks very much for releasing these excellent videos, I have learned so much from you. I have now just completed my first ever computer repair, RAM chips on a 48k Spectrum, I would not have attempted it without first being shown so much by you. Keep up the great work :)
I'm really glad to hear that!! It's great when my videos inspire people to do it themselves! Keep it up!
Nice repair. This computer was unknown to me. Looking forward for the next video with ql
Thanks! Yes, more coming soon. I'm enjoying the QL so far.
Great job Noel. 2 QLs back from the brink.
Thanks!
Great job. That board you've made was extremely useful.
Thank you very much! 😃👍
This was one of the most enjoyable videos I have seen. Very good job indeed.
Excellent intro to QL repair... thinking of getting one!
You should! It's a really interesting device that keeps getting better with time.
I recently fixed an Apple II+ clone that had all the memory soldered in, I used the thermocouple on my multimeter with a bit of heatsink grease. I let all the chips warm up and noted all the temperatures and found that 1 of the chips was COLDER than all the rest ~8c. Replace the chip & fixed it. It's not always the hot chip that's faulty.
Also: the ROM socket is now potentially faulty, you have stretched the leaf springs by inserting the machine pin socket pins. I recommend you replace them.
Very interesting! I wonder what the output looked like on that IC.
@@NoelsRetroLab There was nothing obvious using the scope. I believe it may have had faulty CAS/RAS inputs or open VCC to some internal parts making it not do anything. Just to clarify they were 4116 DRAMs all same make & date code, once warmed up they all were 36 to 38c except for the faulty one at around 29c.
Tip about removing the ICS without a desolider. Cut the IC pins and remove. Put lots of flux on the remaining legs and use pincers and the iron to remove one leg at a time. After this again flux and this time heat the hole and use a cocktail stick to rotate the hole open. Remove the iron and it stay open ready for the socket with no damage or stress :)
Personally, I think it's fascinating that the green and red power up hash pattern was almost identical between both boards! Guess I'm just used to expecting random garbage out of memory at first ... presuming it is sourced from RAM, I'm only 10 minutes in so far but loving your approach Noel!
Edit: That same display using Q-Emulator is notably different! Must say, I love these kinds of puzzles (so to speak!)...
Possibly relevant to someone, you should note that the Interrupt control on the 68008 is different too, just two pins and the ordering might be different on the legs ... IANAE Ymmv etc 😀
Hey Noel good to see you again.
I hope all is well.
Wow, that was some information. Your test ROM seemed to work great
Thanks! Yes, that ROM was great. I plan to explore it as the replacement OS in the future too. I'm told it's much better than the original OS.
look forward to the next one
Very keen to see a power supply build, I need a replacement for my QL
I am too... but it's looking pretty complicated. It won't happen for this month, but it's something I'll keep in the list and try in the future.
Here is a vid adapting an ATX supply ua-cam.com/video/l8P8wsdjCFo/v-deo.html
Great work, always interested in the QL
Great to hear! Thanks!
Great video! Good troubling shooting techniques.😁
Thank you! Glad you enjoyed it.
It is interesting the cost cutting things Sinclair did with the QL like the Microdrive connectors, yet they included a very expensive expansion port connector when it should have just been a edge connector, and the socketed chips when they could have just been soldiered in.
Fascinating stuff, thank you.
Glad you enjoyed it
I remember my father having one of these when I was young. It was mostly something curious to him though as he had Sparcststions in the same shed as the ql along with an xt!
A fascinating computer.
Unbeatable value when it was released.
If I wasn't still programming for CP/M at the time then I would have bought one.
Pity about the microdrive system.
Those sockets resemble thew ill fated SIPs...
Great video Neil :-) I'm just getting a QL back to life and used your little circuit for the Minerva ROM, which worked first time! However, with the M27C512 and the 7404 in sockets I can't get the keyboard back in place, as the new ROM board in the existing socket is too tall. How did you get round this? Or did you only use the Minerva ROM for testing, then take it out and put the original ROMs back in before putting the keyboard back? I want to be able to reprogram the M27C512 in future if there's a Minerva update, or I fancy another ROM, so soldering it onto the PCB board would make the M27C512 unprogrammable, as the wiring from the header pins to the M27C512 will be for an original Sinclair ROM. I'm considering doing a new version of your board, with the M27C512 and the 7404 solder directly to the board, but adding some jumpers so that the header pins either go straight through to the pins on the M27C512 for use when programming it, or switch the pin connections around to use the wiring as in your diagram. I reckon I'll only need three two position jumpers to achieve this, or do you have any other suggestions?
You can make simple inverter using 1 transistor and 2 resistors. Or, even simpler, 1 MOSFET and 1 resistor. That would easily fit inside the chip socket or on top of the chip (for more permanent mounting).
Yes, it just goes to show my background that I'm more comfortable with an inverter IC than setting up the transistor 😃 But you're totally right.
The color of the screen that ends up with (green or white) when booted - might be an indication of the lower or upper RAM failure you think? this could be a starting point to investigate - Great job btw :-)
Interesting! It didn't occur to me. I'd be surprised if the technical manual didn't mention that when they explicitly called out white and green, but who knows! If I had more chips socketed I could try running some experiments 😃
@@NoelsRetroLab Thank you! I will start with my QL which comes up the same way (white) for starters :-) Keep it up please!
Great video as always, Noel!
Do you have a link to any diagrams for the wiring and which pins are not connected through the PCB? Wanting to build this up but a bit tricky to see exactly which pins are not soldered or connected. Thanks.
ICL produced a rather rare variant of the QL called the "One Per Desk" which had a built-in telephone as well as a voice-capable V.23 modem which allowed it to answer phone calls and provide interactive menus to callers with its onboard speech synthesizer. It was developed in cooperation with BT and was marketed by them as the Merlin Tonto and by Telecom Australia as the Computerphone.
As soon as you said "not one but two QLs" it was time for your upvote (-:
Oh Oh Oh... Sinclair QL... a treasure.
Another fine video from Noel just on time at the end of a terrible day at work. I wonder if we will have a #DECember next month :-) That would be a challenge too, but nothing that Noel could not solve ;-)
Thanks! There's the possibility of a #XXXcember but I haven't confirmed anything yet 😃
Does it matter if you would use an EEPROM or EPROM? The one you have in this video seems not to be available anymore (at least I didn't find a reasonable priced one). And newer EEPROMs seem to be only available in 8DIP version. What do you recommend?
It shouldn't matter if they have similar pinouts. I don't usually use EEPROMs, so I don't remember off the top of my head, but if they do, that'd be fine. However, 27CXXX EPROMs should be very easily available everywhere for pretty cheap. It doesn't matter too much if they're 256 or 512 as long as they're big enough (you can duplicate the data inside if you want).
My mum was at a jumble sale, at the village hall. Back in the mid 90s. She knew I was keen on computers. So got me a QL. Was boxed. had some microdrives. It did work. But the microdrives were a bit unreliable. Hey it is a sinclair. Think I just put it in storage. As was more interested in 8 bit computers
My heart lies in 8-bit computers as well, but this seems like a fun system to explore. Next episode I'll focus on microdrives, so that should be fun.
Subbed, this content is so interesting
Awesome, thank you!
Also, there is a great maintenance guide from Sinclair that is online on the disassembly and assembly of the machine.
Haha, I should have started there I suppose! I'm used to just opening them up, but never had this much trouble with a computer before.
Interesting I still have mine but have never touch it for some time now.
And as I packed the boxes to move house some 14 years ago. Wow has it been that long.
Sorry about that. I might try and find it . Looking to see what you make out of them. I was always working on spreadsheets and info for my job.
Time to take them out and try them. Maybe you're lucky, and if not, it could likely just be a RAM problem like these. Do it! 😃
@@NoelsRetroLab yer. Thanks for that. 😄
Good video. I'm sure you know the 'laser' thermometer is just an IR thermometer with a laser pointer. I hear 'laser thermometer' very often in UA-cam video's. Not sure how many people think the laser actually measures the temperature.
Muy interesante este video, gracias por compartir tus conocimientos.
Hey Noel, when you built that ROM adapter on perfboard, i was thinking, wouldn't it have been possible to place the Inverter IC inside the footprint of the ROM? If so, the board could probably have been made much smaller. Perhaps that might be worth considering, should you decide to install the Minerva ROM permanently?
yup i had the same thought... and solder the wires on the bottom..
For sure! That's the smallest size board I had around, but if I make one from scratch (which could be interesting) I can do that, or even use an SMD inverter (or a transistor) and put it under the EPROM but still on the top side.
@@NoelsRetroLab yeah, a transistor should actually be quite sufficient.
A Dremel will cut that board down in no time at all.
While you're in there, can you expand the data bus past 8-bits, increase the color palette beyond 8, and maybe bugfix the Microdrives and add rudimentary sound? The QL is just so close to greatness.. it just needs a few tweaks.
Excess long undamped CS, RAS and CAS lines in dram chips causes this types of ram burning. That's the why some computers put mild resistors over CS to prevent ringing
Really?? I often wondered what makes DRAM so fragile. When you mean undamped are you referring to ringing around the top of the raising edge? Why would it cause failure, because it triggers transistors inside multiple times as the signal oscillates? Fascinating.
@@NoelsRetroLab Precisely. The longer lines tend to develop inductance and this, combined with high frequencies can cause undershoots and overshoots that eventually burn the input transistors or make the part collide with some other device in the bus. This is a pretty know issue and there are lots of possible mitigations. There was some extra info in old National instruments Databooks. Also, this explains the "per board profiles" needed for the FPGA Memory controller IP's. (Compensate delays and timings mostly)
I remember when these came out, I think it was Boots who had these on display, or Smiths. Didn't know they were 68000 based until years later.
That motherboard connector reminds me of some I have seen in audio recievers. Not identical but similarly obtuse.
Great! I wanted one when I was a child, luckly my parents didn't buy one for me :o)
A little trivia: It was Linus Torvalds (creator of Linux) first computer.
Haha, you missed your chance of being the creator of Linux! :-)
@@NoelsRetroLab Lol, I could get one now and be the SECOND creator of Linux, whatever that means ;oP
Those machines have a reputation of being unreliable, not only because the microdrive, also the firmware was plagued by bugs, and you have seen the construction quality. Apparently they were rushed to the market in an early state.
Good job, as entertaining as the 8bit guy, keep on it.
@@NoelsRetroLab I think there was a version of Minix for the QL?
@@ernestuz Like everything Sinclair did, rushed, full of bugs, crap quality, over promised, under delivered and unreliable. It's a miracle any of them survived :)
I saw one of the first in the UK at a local computer club (I also saw one of the first Mac machines in the UK at the same club)
@@M0UAW_IO83 Oh, Minix, had forgotten it, I remember it from College, and yes, googling for it, apparently there was a version for the QL.
Very beautiful machine
Thank you .. very educational and usefull
You are welcome!
The QL was available in so many shops here in the UK in the eighties, but until this day I've never known anyone that actually bought one.
I think they were trying to be a serious business machine but they just didn't cut it. They weren't cheap enough for the home user as the Spectrums were (and there were pretty much no games made for them) so they didn't really appeal to either market. The QL was a costly exercise for Sinclair and they never really recovered from the losses.
@Apple yeah Sinclair really didn't want the QL to go along the gaming route. Trouble was, anyone looking for a "business machine" overlooked the QL too. It didn't look professional enough and it still had a similar keyboard to the dodgy Spectrum + one. The decision to go with Microdrives instead of floppy disks was arguably a poor decision too.
Awesome video!!!
Great looking machines. Shame Sinclair didnt make them to be compatible with Spectrum Software. Great vid Noel . Look forward to the next chapter .
Possible it may have been more popular if they had at least had some level of compatibility.
@@bionicgeekgrrl It probably would have been a popular feature, but unfortunately that would have meant sticking with the Z80. Adding a Z80 along with the 68008 to the QL would have pushed up the cost, and as you can see, this is a very cost-conscious product!
@Apple You are right, of course. I did work on a z8000 system once - part of a flight simulator - but that was the only application I came across for it. Sinclair would almost certainly have ruled out anything 16-bit on cost grounds. Zilog are still around, and still selling Z80s, amazingly!
This belongs to a time period when breaking compatibility was not as tremedous as today. The same year, Apple shipped Lisa and Macintosh with zero compatibility with the Apple ][ as well.
On my IBM 5150 I tested the 4164 ICS by piggy backing a good one on top one by one. It helped me find a bad one stopping the pc from booting, it might also work here with ql memory issues
I used to have one and upgraded it to 896k of RAM and a Minerva ROM. It’s a pity Alan Sugar dropped it when he bought Sinclair Research. I suppose he found it too difficult to reengineer to add a proper disk drive and keyboard.
I wondered ... What’s the blue tape for? Rewind a bit a of couple of times ... oh, I see ... antigravity. 🙂 Question ... Do you know why Sinclair did not use a power switch? It seems like an odd thing to cost reduce.
Haha, I see you figured it out. It can come in really handy some times! The switch... mostly to save a few pennies I suppose. Someone mentioned that in the UK every wall plug needs to have a switch and that was the reason, but it seems a bit of a stretch.
Nice video. Thanks Noel. That small vice, you have link to that ?
You're welcome. Glad you liked it! It's a PanaVise 201. Love it! www.panavise.com/index.html?pageID=1&page=full&--eqskudatarq=1
Noel, after your video I decided to buy one QL, Spanish version Issue5 ooooooh not the last :) that my hands over it right now, ready to open it. I have the white Screen, so I guess it is a RAM chip. :) so double thank you... just... Where is the scheme to built a minerva board?
Nice!! Yes, that looks like it's a RAM chip, so it should be pretty easy. No scheme, just follow the graphic I showed in the video. Or send me a message and I can send you close up pictures if you want. It's just 3 pins that are different, so it should be pretty easy to make.
10 cents investment in better connectors would have caused Sinclair to go bankrupt even faster... :D Nice repairs Noel! Looking forward to more #QLvember content, and maybe even other 68k based machines on the long run... :)
Haha! Or maybe more people would have bought the machines and they wouldn't have gone bankrupt! 😃
Sir Clive should just have refrained from making his C5 electric tricycle - that disaster was a major cause of his comapny's downfall; at least that's what i think.
@@BertGrink The C5 and QL, which I remember being described in the computer press at the time as a "fiasco" both helped to contribute to the demise of Sinclair Research. It was reported that Sugar got Sinclair Research for a fraction of its actual value.
@@captaincorleone7088 Yes, with _both_ the C5 _and_ the QL, it spelled doom for Sinclair, but i wonder if it hadn't been for the C5, if he could have kept going long enough to make the QL moderately successful.
And yeah, Alan Sugar got the company for peanuts, I think he paid around 5 million £ for the whole deal, and there was unsold stock in the warehouses at least worth that amount, from what i have heard.
@@BertGrink That's correct, £5m and the company was valued around at least £15m. IIRC it was reported at the time that Sugar essentially got that unsold stock at £1 each!
I agree with you about the C5: that thing was slated in the press, it was a public relations disaster! At the time I was a kid but I still remember how savage the media coverage was.
Well, that was quite easy!
Nice for a change. Especially with a completely new-to-me machine like this one.
Is it me or is the original IC15 on issue 6 discoloured? My eye was drawn to that chip originally and strangely it's the defective one...
True! Surprisingly, I didn't notice while I was working on it, but it looks like about half the test was somewhat faded/erased. I wonder why.
Love the fact they rev'd the board but didn't include a fix for the ULA bodge.
Haha, very true! I guess that would require making a new ULA design and would cost money!
No the plan was probably to fix the ULA at some point, so they did not want to change the boards to fix the broken ULAs.
7:11 The diagram shows a 6808? Is that an error in editing or in the diagram? Also refers to "MC6800"
Wow, I didn't even notice! That's an error in the datasheet itself! Notice that it's correct in the footer text, but not on the IC itself. Good catch!
I wonder are there FPGA replacements for the SINCLAIR QL ULA's?
Do you know that QL stands for Quantum Leap? Sir Clive tried to market this as a 32 bit computer (leaping from 8 bit straight to 32 bit; he actually appeared in the TV adverts jumping over a pile of computers) How did he arrive at 32 bit? Perhaps by adding 24 address lines and 8 data lines?
Yeah, I've seen that commercial. Hilarious! Maybe at first they were going to put a 68K CPU. Not sure. I'll get into that a bit more in the next video.
No, he arrived at 32 with what really matters: the CPU registers (all 32bits, including the program counter, even though the physical addressing could only offer 20 lines). How IBM arrived at 16 bits for the 8088 is a real mystery, however. The bus was 8 bits and it could only address pages of 64KB at a time just like a Z80... Or maybe the Z80 was 16 bits all along and the Zilog marketing department was incompetent?
Those push in wire connectors were common in audio during the 90s for cost saving. Terrible to work with. One of the reasons I gave up audio repairs. You could only disconnect a few times before the connector broke or the wire end unraveled. I have shouted many curse words at them over the years!
I'm wondering if it's possible to change that so hot 7805 regulator with a cooler modern replacement. It's just that I don't like things running so hot if you've got more (sometimes a bit of expensive) options.
I'm sure it is. We just need to figure out the current rating for it. I suspect 1A might not be enough.
@@NoelsRetroLab Searching I find this: blog.tynemouthsoftware.co.uk/2014/11/zx-spectrum-voltage-regulator.html
qlforum.co.uk/viewtopic.php?t=2117
This delivers 1.5A: www.digikey.com/en/products/detail/OKI-78SR-5/1.5-W36H-C/3438675
@@FernandoelChachi Thanks for tracking that down. I might have to look into getting one of those :-)
@@NoelsRetroLab That will be very nice if it can do the job.
I wish mine was that easy to fix. You could make a fortune selling those ROM boards. LOL.
I think you need to cover the quartz window on the EPROM to stop the EPROM being erased.
I was thinking that too. I once tried to make a PCB by the UV-resist method. I didn't have a UV light, so I used sunlight. I expected not to get enough UV light, so I waited longer than I thought. The PCB was over-exposed.
Great work Noel! BTW SinclairQL was for Sinclair Labs big mistake and make a trouble for a company. Regards!
Totally. Probably the main reason they ended up folding and selling to Amstrad.
@@NoelsRetroLab I believe that the C5 was the main reason. Clive put a lot of 'computermoney' in that project and it was a disaster.
@@xXTheoLinuxXx Funny to see that 40 years later, the big tech companies are trying to push for the same areas that Sinclair foresaw beyond home computers himself : the car, the watch, the TV.
@@chirchir8126 true. Sir Clive had a lot of good ideas and was a visionair back in the day. He spend a fortune because he thought electric vehicles were the future. Besides electric cars we now have a lot of e-bikes in The Netherlands.
If there’s a QLvember I would want a Maycintosh too :)
m68k gang rules!
Don't worry, I suspect we'll soon have a month booked for a different system 😃
1:10 - not just the powerbrick, what was *not wierd* about the QL? ;)
Mijn eerste computer 🙂
I remember fitting a Minerva ROM in my QL in 1991.
Are people still trying to use these things now in 2020?
They're more fun now than they were back then! 😃
Nice adapter board, another way you can make that board is with wire wrap headers.
True! I don't have any but I just looked them up and that would also work well.
nice job Noel!.. them connectors had me face palming, here i am thinkin Sugar was scruge! seems Clive had that covered!
Seriously! That was seriously cheap! That's only a minor step up from the hot-glued ribbon cables of the SVI 328/728!
Later QL revisions (probably starting when Samsung took over production) have proper connectors there
@@NoelsRetroLab You gonna replace them with a proper connector?
@@PJBonoVox I was wondering the same
@@PJBonoVox I hadn't thought of that, but it would be a good idea! Although I'm more concerned about the microdrive connectors than the LED ones. I might try something on my QL.
did you ground or pull high the rest of the gates on the inverter. if you leave them flapping in the breeze thats exactly what they do and cause noise
Interesting. No I left them flapping in the wind. Do they really cause noise on the one gate I connected? More than if they were switching following some other logic? When I make a more permanent board I'll make sure they're grounded.
@@NoelsRetroLab it's probably not a issue but it's good practice I've had issues that had me stumped for ages because I used to leave them floating but I talking more high speed things another idea is to tie them all together as one big gate
Was this machine compatible with the zx spectrum software or not at all?
I am glad you were able to figure which ram chips were causing the issue. I have more than once had to keep swapping ram until I guessed right. I know there are Arduino Ram testers for the 4116 and 4164 so I should probably make them.
Not at all! Sinclair aimed this machine at a completely different market. I'll get into more details next video. But I'm sure that was part of the reason it was a total flop.
RAM testers are useful, but usually you need to remove the RAM from the board, so it wouldn't have helped too much avoiding the desoldering. And there were 16 ICs! Yikes! 😃
The ZX Spectrum used a Zilog Z80 microprocessor, whereas the QL used the Motorola MC68008, these are two completely different CPUs.
@@NoelsRetroLab After the Amstrad takeover of Sinclair's IP, a consortium was formed that obtained the rights to the QL IP, this resulted in some moderately successful machines such as one called Thor, and another called OPD (One Per Desk) which had a built-in phone as well as a modem, thus requiring two phone lines.
The main reason i remember that consortium was because the official danish Sinclair distributor, Dansoft, was one of its members, and the magazines here in DK were quite excited over that. ;)
@@BertGrink I didn't know about that. Very interesting!
@@NoelsRetroLab Here's an article about the OPD en.wikipedia.org/wiki/One_Per_Desk
and there's a _little_ information about the Thor and other clones here en.wikipedia.org/wiki/Sinclair_QL#Clones
Those microdrive slots would house an SD card reader rather nicely. Just need to replace the 68008 with the better version and it'd be a decent machine.
They certainly would fit nicely there!
Excellent! Learned a lot though the basic principle is the same.
Great to hear!
Haha - I had exactly the same experience removing those wires :-D
Linux founder Linus Torvalds used to have a QL!
Weird they placed that microcontroller at the border of the board. We usually avoid that like heck as restricts the pathways we have available for the tracks.
Yes, the whole layout is a bit weird, even with the CPU off to the side like that. But at least that's next to the expansion bus, so that kind of makes sense. The board is also super crammed, so they were working with some big constraints (maybe from design first).
You said you are a game developer and you wear a Steam Dev Days shirt. Do you sell games on Steam? It would be a nice way for me to support you. :-)
Great video! Love it. Glad you joined the #QLvember. Here's my QLvember contribution: ua-cam.com/video/cxs6d108Mnw/v-deo.html In this video I talk about the Sinclair QL Service Manual, which is much more than just a pure Service Manual as it also contains at least part of the QL's Engineering Specification. I also show some ultra-rare original still uncut QL PCBs and talk about details. QL forever! Cheers and stay healthy!
Nice! I just watched it. That service manual was great! I definitely referenced it a lot in my research for this video, but only the digital format unfortunately (I"m a sucker for a good paper book!). Thanks for sharing it! Subbed too 😃
Noel, What I usually use is this kind of vero board: ebay.us/1XN1eu this way you don't have to solder all the traces. But a very good idea to solder the pin headers in the same holes...
Right! That makes sense. I guess you'd need two different ones, one of each half of the EPROM, right? I should have a few of those in hand. Thanks for the tip.
The link is dead. Can someone explain what he was kind of stripboard he was going to show?
1:30 serious business styled hardware.
Sony fans: is that a Playstation?
Wow the ol' 68008. That means the QL had to make 4 accesses just to read/write a 32 bit value. Ouch! But nonetheless.... still a more powerful processor than the older 8 bits and I'd put my money on the 68008 over and equivalent 8088 or 8086 any day at even twice the clock.
Yeah, that bus is a huge bottleneck. I'm surprised Sinclair didn't go for a 16-bit bus. It must have been much more expensive I suppose.
@@NoelsRetroLab Motorola aimed the 68008 at manufacturers who wanted to save a few pennies, because it needed fewer lines and thus motherboards could be smaller and cheaper to design much like the 8bit motherboards of the time. They were just imitating what Intel did by introducing the 8088 time after the 8086 was released, for the same reasons.
In the end, it became more expensive for Motorola to manufacture the 68008 than the 68000 (lower economies of scale) so they stopped producing it quickly.
Me gustaría experimentar lo que es picar un texto largo en el QL.
Who signed off on all those connectors, they are the weirdest things I’ve ever seen in my work in electronics especially that case one with the loose wires, like you say imagine the savings in time in production if it were just a regular push fit connector! Who even made that kind of connector?! Never seen one before. Those Microdrive wires, push and pray I call them. The sad thing about the QL is there was a saleable, value for money winning machine buried in a pile of junk, such a missed opportunity.
Right? Right??? 😃
I would guess the reason that Sinclair computers originally didn't have power switches is that in the UK, all wall outlets are forced to be switched by law. So you were supposed to just turn them on/off at the wall.
Sir Clive was just a cheapskate. :) Other UK contemporary computers had power switches. His entire business strategy was to cut corners in order to cut costs wherever possible. There's another video Noel did which showed that Sinclair bought up faulty RAM because the Spectrum wouldn't even need the full capacity anyway. :D
Oh wow! I had no idea, but that would certainly explain it a bit better. Are the switches next to the outlets, or are they like the light switch as you enter a door?
Next to the outlet on the wall
Unfortunately that's not true, sockets aren't 'forced to be switched by law' at all.
As Corleone says, the reason was probably that Clive Sinclair was just too cheap to fit switches or buy full spec components, he had long history with buying factory reject parts for his products and it wasn't limited to the computers.
@@M0UAW_IO83 Sorry, my mistake. A better way of phrasing it may have been "nearly always have a switch". I agree he was a cheapskate, even if this was part of his reasoning, it was a thin excuse at best!
These El Cheapo connectors are testament how expensive microelectronics were way back when, and how cutthroat the Homecomputer market was.
I know this is a but of a long shot, but can anyone help me with a weird zx spectrum problem? My dad gave me a spectrum (the very first version) that was in pretty bad condition. I replaced the capacitors and the keyboard membrane circuit thing, and tweaked some variable resistors to fix the colours. Everything works ok now, except that if I try to type a basic program in, after a while the screen corrupts weirdly, then it crashes. It kinda feels like the basic program is starting to overwrite video ram or something. Is this a known thing, and does anyone know how to remedy it?
Edit: I only have a multimeter, not an oscilloscope, sadly, and the screen corruption is pretty hard to describe. The characters start to deteriorate, and the corruption even changes a bit when I keep typing, then it tends to lock up and crash
Hmm... I would suspect bad RAM. If you have a way to load the ROM from ZX Diagnostics, it can pinpoint it right away. Since your Spectrum is working, I think they even have a TAP version of the test. Stop by the Discord server and bring this up, that way it's easier to post pictures and discuss that. Good luck!
@@NoelsRetroLabThanks! I'll see what I can do, though I think there might be an issue with the audio input too, sadly
It might be a ram chip failing as it warms up. See if one chip gets hotter, like Noel was doing. Otherwise, try using freeze spray on each chip and see if it lasts longer before crashing. Don't give up :)
@@tenmillionvolts thanks, I'll try that too. Problem is, it's an original spectrum, the whole thing gets very warm very quickly XD
Thank you for the video, Noel:)
And me again, hehe: Are you sure you want to leave the unused inputs on the 74HC(U)04 floating?
Admittedly, I can't really see that on the video, but if I'm right, then in contrast to the 74xx or 74LSxx, it can give a nice -function- noise generator:)
Also 74HCU devices do not match 74HCT or 74(LS)xx TTL-levels which match M27xxx style EPROMs.
See electronics.stackexchange.com/questions/384672/74hc-hct-what-to-do-with-unused-inputs-and-why or your 74HC(T) datasheet for a deeper dive.
And Nexperia/Phillips HCT User Guide, page 30 - 7.4 Termination of unused inputs and Table 11 on page 40.
But that is nothing against the noble deed of reviving these wonderful machines. Great work!
10 cents was worth a lot more back then than it is today.
sinclair were all about building down to a price, which is why you found connections you weren't familiar with, they would have used the cheapest parts they could find
Nice video. The hardware of the QL never was really good, the magic was in the very innovative operating system. And the case design IMHO :-)
Minerva writes one 32-bit word in 16kB increments and reads it back to see how far the RAM goes. If that happens to be one of the failing addresses then the RAM is just cut short as distinguishing between "failing RAM" and "no RAM" is quite difficult. Especially with Minerva, which is so packed full of features that it almost has no single byte to spare in its 48KB area.
Right. Especially after they ironed out some bugs from what I read! That makes sense about having a hard time detecting the difference. It's curious that it does once in every 10-15 times though.
@@NoelsRetroLab Yes, can't quite explain that, the data it writes in that phase is constant and not randomized like the main RAM-test (actually it's just the address, i.e. $0003000 in your case). Maybe the bits are flaky and occasionally work.