The Sinclair ZX81 for n00bs *GUIDE* in English

If you're looking to buy a Sinclair ZX81 computer then this video will give you an introduction to this 1980's classic. This computer was launched on the 5th March 1981 and apart from it's predecessor - the Sinclair ZX80 - it was the only home computer just about everyone could afford.
They sold 1.5 million.
Here are a few notes to clarify what I say in the video.
You can see the range of Sinclair products by looking here: rk.nvg.ntnu.no...
This includes the calculator mentioned. And the ZX series of personal computers. And all the other stuff they made.
For context, this is a flavour of what else was happening at the time...
www.computerho...
Essentially, the ZX80 used 21 chips on it's circuit board compared to just 4 on the ZX81. This was because the ULA used in the ZX81 collected together important functions from several chips into one - reducing manufacturing costs so significantly that the ZX81 was actually launched at a lower price than the ZX80. It also enabled increased production and kits were easier to self build.
Just over a year had passed since the ZX80 was launched so converting a ZX80 into a ZX81 simply required an updated ROM chip and a keyboard layout sticker. This was a thoughtful consideration of the Sinclair customers that had bought the ZX80 only to see it replaced almost immediately by the ZX81.
So large numbers of ZX80 owners upgraded and now original ZX80's are rare.
Full comparison can be found here: www.primroseban...
It's not just Sinclair chips that had errors... some people might remember the Intel P5 ROM error - when Intel recalled all the initial versions of their Pentium chip - including the one in my first ESCOM tower PC. Read about it here: en.wikipedia.o...
At 8:50 you might spot that the polystyrene is Sinclair embossed. The other RAM pack doesn't have this detail.
At 10:10 it's Posidriv screws - not Posidrive. If you ever wondered why your screwdriver set has PH and PZ bits that look the same or would just like to know more then read about it here: en.wikipedia.o...
At 10:40 you might spot the little plastic crumbs from the removed screws. The plastic is 40 years old so I don't advise dismantling this kind of hardware unless you really need to.
At 14:08 the catalogue shows the 8k ROM upgrade for ZX80 owners. You can usually tell if the ZX80 has been upgraded because the ROM came with a ZX81 keyboard overlay sticker that was put onto the existing ZX80 membrane after the ROM was swapped over. The original ZX80 had a blue keyboard - the ZX81 is black. A lot of the ZX80's on eBay have the black ZX81 keyboard.
At 14:50 my preferred brands of tape are 3M and Tesa. You can also buy the little rubber feet separately if you need to replace the ones on your ZX81. This is actually important if you'd like to reduce the chances of RAM Pack wobble.
At 17:37 the first two numbers are the year and the second two are the production week. So every ZX81 can be dated. It's not exact though - you can get older ULA's in ZX81's that were purchased later than the initial first few. The other chips present can help - two RAM chips rather than one, the type of Z80 and the ROM are also factors. There are also special rare versions with soldered modifications too. Some even have serial numbers on them. Considering it was only available from 1981 to 1984 the variation is pretty amazing. This makes them interesting to collectors but also within reach of everyone else.
At 19:01 the ULA list can be found here: www.bytedeligh...
At 21:15 here's one list of ZX81 cassette releases: www.zx81stuff.o...
At 25:37 the model is the Fergusson 3T07. There were variations of this model that appear to be the same at first sight. One obvious difference is that the early recorders didn't have the treble slider - just the volume.
Some community links are shown below:
www.sinclairzx...
spectrumcomput...
/ zx81ownersclub
I'm never going to get rich from this, but it is nice to get something... So if you've watched this video and it influenced or helped you then please click Like and Subscribe.
You can also buy me a coffee using the Ko-fi link if you think I deserve one...
ko-fi.com/nicb...
#retro #zx81 #sinclair