Repairing and Restoring a 43 Year Old Computer - Sinclair ZX81
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- čas přidán 5. 09. 2024
- This ZX81 is showing no signs of life and needs to be fixed! A mod and clean up are also on the cards.
ZX81 composite mod:
github.com/red...
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I suddenly realize what has been missing in my life the past few weeks... It's LEE FIXING OLD COMPUTERS!
I'm like that itch you cant reach. Basically I'm a bit like athletes foot.
@@MoreFunMakingIt haha! No, seeing your video appear in my subscription feed seriously brightened up my day, as the past two weeks I’ve been ill (covid?), low energy, and very grumpy, forgetting good things exist, like you and your channel (did I just call you a thing?!?)! So thanks!
Good to see a classic being restored. The ZX81 was my first computer, and it sparked a passion that is still going strong 40 years later.
I hear the same thing from many others. Such an important little machine.
me to
all the way to running my own IT consultancy company
Same here, I got mine back in 1982.
... and a sticker for the eventual owner to remove in disgust 😁😆😂🤣 Nice work!
I will send you the file so you can print your own and stick them to everything in your house :D
Love the ZX81 it was my first computer I owned in 82
Same here! Maybe 81, but my memories are vague
@@MoreFunMakingIt had mine to do homework for computer studies lessons but I spent more time playing 3D Monster Maze lol
@@allford1971 I begged my parents for a ZX Spectrum and promised it would be used to do my homework on.
I must have lost the "do you homework" tape... 😂
What a great Friday.
I'm on call for work and its looking very unlikely that will happen.
Then Lee brings out an old Sinclair in need of a tickle.
Happy Friday!
Some of the fans really hate it when you gut the modulator as I learned once. It's still worth it, far better picture.
yes, it angers me when people do it, theres no need at all to murder the modulator to fit composite mods of any sort, they can be fitted outside the can and you wont see it when the computer is cased back up! you can even rig it so its simultaneous rf and composite
@@andygozzo72 Why? Who's ever going to use RF even on a crt.
@@rimmersbryggeri you never know,... it could still be used with a 'period correct' tv, then, most didnt have AV inputs back then, certainly not 'normal' black n white sets..and also things should be kept as original as possible, as i said, you can add composite out without ruining the modulator, this could then be easily reversed if required,
@@andygozzo72 I agree in the event you'd want to use it with a B&W tv it could be useful. But most likely it would be used witha CRT that was also used with other old gaming systems. I think I would prefer an external RF modulator in that case (From a sega MS MD) anyway but that's only me.
@@rimmersbryggeri no need to have an external modulator when the machine already has one! as i said , with a bit of extra circuit you can have both composite AND RF through the modulator output so you can use it either way ...
Subscribed. Looking forward to getting my own zx81 for my own 'computer museum' I have at home.
Great work and attention to detail. You've got the job, can you start on Monday?
Yes. But you'll have to provide transport.
I will most likely never repair a retro pc… But I do absolutely love how you make watching these repairs an absolute joy - I’m even learning the lingo now as well! Not sure what the whole back porch stuff is but I’m guessing it shelters the to from rain? 😉
Amazing work as always and thank you so much for sharing.
Aww thank you J! I did forget to explain the back porch thing. I promise to do that in a future video (although I will mostly be making stuff up and pretending I know what Im talking about)
Lovely machine, my first as well. Great to have a new video on a balmy Friday night, not often i can watch outside! The little ZX81 was probably more useful than many other computers today 😂
So love the ZX81 😍 my first experience with a computer going round to my auntie's house boxing day 1981. My older cousin had got one for Christmas and he was showing us what it could do. My female older cousins definitely didn't seem as impressed as I was. I found it mesmerising and it opened up a fascination with computers I still have to this day. 3d monster maze and Mazogs were my favourite. He seemed to see how impressed I was and suggested I go round again the next day to play again 🤩. Another great video mate with a laugh out load again with the Kenneth Williams bit 🤣👏
The modulator isn’t the cause of the dark image, it’s the ULA. That’s why the 555 timer chip is required, to fix up the non-standard signal that’s being received.
yes, the early versions of the ULA dont generate a 'back porch' pulse which a colour tv uses to clamp the black level, black and white tvs dont use or need this, its nothing at all to do with the modulator, they work properly and give good pictures with correct signals fed to them, and very rarely fail... also even with back porch, many tvs still wont display the picture correctly, even going 'blue screen' as if no signal, my kitchen tv does, its very picky, this is due to non broadcast standard frame sync pulses... i am currently thinking of an alternative way to get composite without any internal alterations, but extract it from the 'mic' socket as this is also fed from the ULA video output pin, but attenuated and low pass filtered, any external circuit would need high gain and reverse the filtering, and likely some 'schmitt trigger' circuit for both video and sync to remove noise generated by such high amplification
I needed this video 40 years ago!
Thank you for your patience :D
i quite like ZX81s as well.
Def with you on the warm fuzzy feeling when you see that K cursor, and it's nowt to do with age either :) Nice job sir.
Cheers! Hope you're well?
Not bad mate, not bad. Happy to see you back fixing stuff again :D
Great job as always mate! The 184 ULA will always need the 555, as it doesnt have the backporch. I'm surprised you didnt swap out the 7805 for a dc2dc and help the wee beastie stay cool.
Cheers Roy! :D The lovely man that gives me all these broken machines to repair has to watch the costs, so luxuries like TRACO's are sadly a bit too expensive for a lowly '81. Hopefully it will have an easy life wherever it ends up!
It's not a proper 81 until it has an added velcro strip for holding the ram pack on !😂 Any oldies will remember the frustration of hours of typing a program only for the pack to fall off before you can save it !
Blue tack! :D
i used matchboxes to lift it up for better ventilation and another to make a wedge for the adjustable ram pack support
Good old Clive, so nearly perfect.@@frombrum
Lovely video. Inspired me to get the soldering iron out this weekend and see if I can get one of my ZX81 working again.
Good luck Ross!
My main ZX81 is heavily modified. I've give it 32K internal RAM, Traco regulator, SD card adapter for saving and loading with modified ROM and a programable joystick port.
I ❤ZX81
as allways great to see another retro computer made useable again!
Started a YTS in Sept80 £32/week.Bought my self a ZX81 for christmass.Ahhh Ram pack wobble, two methods of fixing match stick jammed in the side, or the more exotic blob of blue tac.
Great video as always mate & I know what I'll be doing at the weekend. Digging out my ZX81 & giving it some renaissance wax love 😁
Really makes it look lovely!
oooh some nice motherboard ASMR there at the end. Thanks.
Glad you liked the bit at the end. I thought it was a nice way to finish :D
I used a Sinclair ZX81 in1985, to produce computer generated titles for my Home Video Movies. I created a film, with frames and sprockets, which rolled up the TV screen (albeit jerkily). Inside each frame was the video title. I then recorded the ZX81's video output to Betamax videotape. I still have the Betamax recordings, and the SONY SL-F1 Betamax VCR, and the cassettes still play!
Nowadays, I use NLE software on a PC!
Thats amazing!
@@MoreFunMakingIt What's amazing, is comparing the primitive ZX81 80's CGI video titles, to what one can do 40 years later!
Nice work there. So many memories to this machines
I built a ZX81 from a kit in probably 1981, sold it a couple of months later. eventually bought a used BBC B. Oh and the ceramic thing you drilled out is a feedthrough capacitor.
Ah! Good info. Thank you
Superb work the zx81 made computers affordable i love the looks of them .The one i have i believe has an issue 1 main board no composite mod yet
issue 1 boards were fitted with the early ULA so unless the ULA has been replaced with the later type, it will need a back porch generator type mod...
Nice work Lee! And wow it cleaned up nicely. I need some of that stuff you used on your last step to try on mine. Enjoyed it!
Its amazing stuff. Highly recommend it. In fact its used by big museums to keep exhibits in good condition (not retro museums, PROPER museums!)
Nice wee vid lee, always enjoy one of your repair videos 😊 This really makes me want to get going on my ZX81+plus38 build ive not yot round to ...
Same here! Really must got on that...
Nice Fix. Tidy work!🏁
Great drums+bass groove. Made me get up and play my drum kit, which I haven't touched maybe more than 6 months. 🙂
I will pass that on to the lovely man who made that track for me :D
@@MoreFunMakingIt Tell him to keep them coming!
Thanks for sharing. Never used Renaissance wax before but looks like something to add to my kit.
It's a little expensive but it lasts forever. Well worth the money
goddamn youtube not giving me notifications of your new videos, just saw this, great video
Nicely condensed! ❤
I recently did a "spring cleaning" on my Engineer manual sucker! It was full of solder and other debris, well past the nozzle!
I love how well it works after a good clean
Put a part of a silicone tube on tip of vacuum pump, beter contact, protects board and tip.
Lovely to see Lee!
Good job mate - and nice clean up job at the end!
Cheers!
Congrats on your channel. I really like the way you format your videos. About that wax, it was a really nice touch. Can we get the brand your using? Should one take care to find a plastic friendly wax or any brand will do? Thank you!
Hi! Thank you :D The wax is called Renaissance wax. I would not put petroleum based waxes on plastic so be careful what you use.
Thank you for bringing back old memories!
My pleasure!
this and the speccy thats what my friends dad had. his zx81 was the kit he brought back from the uk om xmas, mid 80s. he got the dktronics character rom thing you could design your own characters. it had a demo game of space invaders with iy
I remember those addons. I remember wondering if I should buy a load of those (sound, character, colour, all kinds of funky stuff!) and have them all hanging out the back of my 81 or should I upgrade to a ZX Spectrum!
@@MoreFunMakingIt He had bought a dktronics "case" which you out the motherboard into. It had a decent keyboard as well
I bought mine in WHS Burnley Lancashire around 1981ish had to return it the same day with a keyboard fault. still in the attic. I did fail to make a 3k rampack with 2114 chips.
My cousin had a made a kit z80 before my purchase
The 555 timer, what can't it do?
NOTHING!!! :D
@@MoreFunMakingIt eeeeeeee MAGIC!!! :D
Nicely done. Mate.
Cheers Taz :D
My first computer too. I have one in a box somewhere, I just assumed I would not find a old tv to use it with.
1:17 Are you sure the warm feelings aren't just the 7805?
Im very old so there's an equal chance I just soiled myself :D
Another retro computer saved.
Didn't Casio make a similar/same one in '79? (I saw near Bellevue mall just south of the future Microsoft in Redmond, wa.)
Armor All has been the go-to for plastic/rubber since the '80s here in US
You might be thinking of the US version of this computer? The Timex TS1000.
Jam in a TSR-2450.
Muy buen trabajo!!👍
Cheers!
Well.. That was just cool.
That putty is a good trick for assembly. What's the name of that product?
Here in the UK it's called Blue Tack and the company that sells it is Bostik. In the US I believe its called all kinds of things like Sticky Putty or Quick Tack. Should be able to find something very similar. Adrian had something on a recent video about the US versions vs the one from over here.
"wiggle the plug in the socket" huhuhu
i've got a working one on top of my wardrobe if that makes things easier!
Better than it being in a leaky shed!
@@MoreFunMakingIt
i have a fully working boxed spectrum 128 rescued from a skip too!
Who's Zed? Zed's dead!
What's a back porch?
So, my limited understanding was that it sets the black level as well as some timing stuff during each pulse. But I thought I should look it up before I go sharing information, and on StackExchange they say "Back porch is the duration between end of horizontal pulse and start of the next line with video information. Lasts more than front porch around 4.7μs and the main purpose is to give the time to beam scanning for reverse direction (right to left) to start new line. In addition it sets the reference black level as well as sets the timing of color burst pulse."
Which is kinda what I said :D
There's a video on my channel called ZX81 Video Conditioning that explains this and describes how the circuit to add it works. I tried giving a link here, but CZcams just makes my message invisible to everyone.
@JoulesperCoulomb hello Joulesper! Your videos have taught me so much and I still point people to them when asked about how to do initial checks on a ZX Spectrum. It's good to know you're still about!
I don’t know why the 555 is called a timer in reality when it’s an oscillator
Too much BASS.
The music?
@@MoreFunMakingIt yes.