Lets Take A Look At The Sinclair ZX81 (+composite mod)
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- Опубліковано 4 сер 2024
- In this video, we are going to take a look at a Sinclair ZX81, a classic computer of it's time. We'll get it going an do a composite modification on it so it's easier to use on newer monitors.
Carnival Steve. Somerset Carnivals and Adventures. / @carnivalsteve
ZX81 Wikipedia: en.wikipedia.org/wiki/ZX81
The Composite output MOD: www.bytedelight.com/?page_id=...
Music:
'Interstellar-Sentinel-Challenge-4', 'Interstellar-Sentinel-Challenge-3' & 'Interstellar Sentinel Challenge 1' by Chris Huelsbeck, used under a royalty-free license, please visit / chris_huelsbeck for more info!
Chapters:
0:00 First Look
3:26 Testing PSU
8:05 Trying to get RF output
13:14 Teardown
19:35 Composite Mod
31:20 Doing Some BASIC
40:50 Thanks!
@Dave Poo 2 many Many thanks for this. Absolutely fascinating and very interesting to see this being stripped down and a little program being run after 25 years of dust collecting.
My dad sadly passed away in 2017, but he would have loved this. Your video has given us some lovely memories.
The ZX81 was my first computer. It really was the Raspberry Pi of its day. I work in IT today and owe that in no small part to the ZX81. You do get used to the keyboard and input method :)
Around 17:00 the switch might have helped you if it was installed, it switched between VHF CH2 and CH3 (in my case) but converting to composite is absolutely the way to go anyway. 28:00 that grey background indicates the "back porch bug" on those ULAs. The Clueless Engineer does some good conversions on his channel, including using the vLA81 replacement ULA. Yes, the 0/0 means status 0 (program completed) at line 0 (direct input). So 5/10 is "screen overflow" at line 10, use SCROLL to get another line :)
The computer is "slow" because of the way it draws the screen. If you use FAST at line 5 then SLOW at the end, it will be as quick as you expect, but you won't see the screen update 🤣
You're right though, I was over the moon to get one of these at about 11 years old. The only other computer I had really used till that point was an Apple ][ at school. That's one Apple ][, and only in the principal's office because he was on to it and knew where things were going.
Thanks, I knew somebody would arrive in the comments with some of the answers. It's my first time using Sinclair anything, so I am a total noob. Would have been really cool to have one of these when their time was relevant. To build a computer like this, at this price was a big deal back then, as nobody had enough money to throw 1000's at a new home computer, making a cheap learning tool was the way to go. It's a neat little computer that deserves it's place in the history books.
happy new year dave, all the best for 2024.
in 2022 I bought a rubber key 48k speccy and in the box, unbeknownst to me (ebay purchase that it was) was a surprise zx81.. I too was gobsmacked by how small it was. along with some cables, power supply was also a 16k ram pack. at the time i had a 14" colour tv, and managed to get a picture from it over RF. since then the tv has given up the ghost, but I bought an old 26" crt to use with my MiSTer and that TV has an RF on too, so we're all good to go.. :)
Happy new year! A suprise ZX81 certainly is a welcome one. Did they think it was part of the speccy maybe? sometimes when people sell stuff on eBay they don't know what it is, or sometimes they are just happy to get rid of their junk and put it in the box anyway. So which do you prefer typing on? the dead flesh keyboard or the unresponsive ZX81?
The 0/0 is the line number, error code. So no error, and as you ran it in direct mode, there is no line number
you missed out on the joys of the "ram pack wobble"... after spending hours of typing in a magazine llisting, I'd mistakenly nudge the zx81, and the 16KB ram pack would wobble on it's edge connector, causing the whole thing to disappear before I'd had a chance to save the damn thing. (An ice cream stick wedged between the '81 and the ram pack, plus lots of celotape would sort it out though.)
But playing Catcombs and 3D Monster Maze back in the early 80's on that thing was amazing at the time..
I suppose you were lucky if you just lost your program, and if you were unlucky the whole thing would go up in smoke?
Interesting, zx81
Yep, a Sinclair product! on my channel, who would of expected that!
@@DavePoo2 Shock, horror (LMAO!!)
A simple resistor divider should be enough to reduce the voltage going to the TV 👍
After you ran the "Hello World" program, the ZX81 said 5/10; this means error 5, Out of Screen, in line 10.
I think there's a poke you could add to the program so it would keep printing, but I cant remember the details right now.
Oh and the ZX80s and early ZX81s (Issue 1) were notorious for having a non-standard video out signal, something about a weak or missing back porch IIRC. On the Issue 3 ZX81 it was a little better, but still not perfectly standard.
Thanks, I figured the line number but not the other code. I suppose there must have been a manual that came with it originally that described all this? (or maybe sold separately?)
34:22 It is exactly what that error code means. You ran out of screen
Good evening, Mr Poo, or may I be so bold as to say Mr Faeces?
It is I; Mr Meecies.
Cheeses for us Meecies!