Using a ZX81 made from all new parts | PART 2 |
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- čas přidán 8. 06. 2024
- Can you build a ZX81 in 2022 using all new parts? PART 2 Sponsored by www.pcbway.com/setinvite.aspx...
PART 1 - • Building a ZX81 with a...
PART 3 - • ZX81 Mechanical Keyboa...
PART 4 - • ZX81 All New Case Desi...
PART 5 - • I built an All-In-One ...
ALL PARTS - • Building a NEW ZX81+38...
Github (ZX81+-38) - github.com/mahjongg2/ZX81plus38
RevSapce (ZX81+-38) - revspace.nl/ZX81plus38_simple...
Case - www.thingiverse.com/thing:452...
Chuntey Field - www.urbandictionary.com/defin...
Curvy Line KiCAD plugin - github.com/mitxela/kicad-roun...
Mage - revivalstudios.itch.io/zx81-mage
Down - revivalstudios.itch.io/zx81-down
Replacement EEPROM - myretrostore.co.uk/product/zx...
0:00 - Introduction
0:13 - New EEPROM
1:11 - Programming the EEPROM
1:38 - Making the EEPROM pin Compatible with the ZX81+38
2:27 - Message from the Sponsor - PCBWay
2:58 - Loading from WAV
3:14 - Loading from TZXDuino (Both old and new(ish) games)
8:35 - Loading from cassette
10:19 - Mechanical keyboard design
18:06 - 3D printed case - update on progress
20:49 - Wooden case news - Thanks Patrick!
22:05 - Outro
Can you build a ZX81 in 2022 using all new parts? PART 1 Sponsored by www.pcbway.com/setinvite.aspx...
ERRATUM - ULA Bullet point at 1min 08 should read "Uncommitted Logic Array by Ferranti"
PART 2 - • Using a ZX81 made from...
Github (ZX81+-38) github.com/mahjongg2/ZX81plus38
RevSapce (ZX81+-38) - revspace.nl/ZX81plus38_simple...
Case - www.thingiverse.com/thing:452...
0:00 - Introduction
2:57 - Message from the Sponsor, PCBWay.com
3:24 - The Build
10:40 - EPROM
12:30 - Case
13:02 - Testing and using
#sinclair #zx81 #clone #zx81clone #mechanicalkeyboard
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3D Monster Maze still makes me smile! I've got my original cassette somewhere, probably worth a few quid but I'll never ever sell!!
Had a ZX81 & Spectrum back in the 80's and spent ages trying to get games to load, completely unaware that it not working properly was down to me messing up the chuntey field, at least I know now :)
Thank God you didn't have the audio going for the cassette load. That sound gives me nightmares of wasted hours loading dud games in 1981.
Chuntey field? I lived and breathed it!
This is a very similar type of clone as the ZX81NU I just finished building, although I have to fix some issues with mine. It's very similar, using all off the shelf parts, and whilst it doesn't have the joyport, the output jack, and needs a full 9V PSU, it does have some nice features like an onboard 128K EEPROM that emulates the Microdisk, and also has a header in place of the missing jack to connect a VDrive2, which allows using a USB with the software. It uses a custom ROM image with the commands for these features, and both ZX80 and ZX81 BASICs which you choose from a menu when you boot up.
One thing that makes it a little harder to get around is that almost all information and forums for it are in german, which isn't a problem using Google Translate to read, but makes participating in the forums very hard, especially if you're troubleshooting. I have the ROM written on a 27C256 at the moment, but I've ordered a couple of W27E257 EEPROMs to try out, as they are pin compatible but without the UV hassle.
I am considering getting a Mahjongg, as even though I don't need it, building the boards up is always fun, a great hobby to have.
Got lots of vids to check out mate looks like my kind of vids I do love the zx81
Do one in ZX-UNO and Harlequin kit.
Hi, here are some vids you might like then 👍
Harlequin 128K Build - czcams.com/video/CgfEhUEvCR0/video.html
Final assembly putting it in the case - czcams.com/video/5m0rjmKDxPI/video.html
Loading from SD card - czcams.com/video/aQKdRkED54c/video.html
Chuckie egg comparison, ZX Spectrum vs BBC vs C64 Vs iPhone - czcams.com/video/poGuEwI0UpM/video.html
It's a pity you don't have subtitles like part 1... It is understandable, but some times, we, the not native English speakers, can have trouble.
Thanks for the feedback. I'll look at getting some uploaded.
Nice video, will you be releasing the keyboard PCB Gerbers or selling them on your website?
Thanks, once tested I’ll upload them to GitHub and PCBWay’s maker area.
Hi, just uploaded the subtitles 😁👍
@@iNimbleSloth let's go to see it again... ;)
Great, a few tips from me, the designer of the ZX81+38, Martin de Jong (AKA Mahjongg):
If you want to test the level of the audio signal, with a real ZX-81 you could look at the screen while loading, I have added logic to my clone, so that you can do the same on my ZX81+38. Unfortunately if you start a LOAD"" the ZX-81 will stop generating a video signal, and with a modern TV the screen will switch off (turn dark). The trick to still use the loading bars to estimate the loudness of the signal is to simply not start loading. If you then enter a cassette signal the loading bars will appear, and you can determine if the signal strength is low. The thinner the bars the lower the signal is. When using the TZXDuino the bars will be nice and fat. Regulate the volume of a cassette recorder so that the loading bars are reasonably fat, then rewind, and start a real LOAD"".
Obviously you can use the adapter for an 28C256 in SMT as shown here, but what you can also do is using a Pin trough hole EEPROM, the 28C64, which can be bought from Reichelt for less than ten euro, see here: www.reichelt.nl/us/en/eeprom-64-kb-8-k-x-8-5-v-150-ns-pdip-28-28c64-150-p1946.html?r=1
And yes, you have to change wire jumper JP10 on the back of the ZX81+38 so that pin 27 will stay high.
the 28C64 is an 8K (byte) ROM, so you have to write the ZX-81 ROM only once.
Hopefully the chip shortage will be over soon, so you can buy a 27C256 again.
(Now in April 2023 it seems you can again get the 27C256 again for a reasonable price)
My own idea for a case (if you don't own the case of a defective ZX-81) was to use laser cut plywood. But I did not manage to design one yet. But I have made a start for one for my color computer design (still in progress) Rhococo (Retro Home Color Computer) see here: revspace.nl/Designing_an_enclosure_for_RhoCoCo.
but there are many people busy inventing cases for my clone, including one built out of LEGO. designed by Alban Killingback. He posted it on the LEGO side rebrickable, see here: rebrickable.com/mocs/MOC-129979/akilling/lego-case-for-zx81-plus-38/#details
I received my own PCB's from PCBWAY, so I'm building my own revision 1.9 copy now, I do have a ZX-81 case so will mount it into that case, including my keyboard, I noted I have to use a file to take of a bit from the left side, for it to perfectly fit into the indented part for the keyboard foil of the case, but it will fit. I will use 6x6mm keys with short key stems and a low travel, so I can glue my keyboard overlay on to without having to create holes in it for long key stems I used in my prototype board. I will test how well this works, then photograph the result for my raspberry PI forum page dedicated to the ZX81+38, where you can also comment on my work, and show your copy of my clone.
The lego case is awesome! I'm quite tempted to build one 😊 Thanks for the link for an alternative EPROM. I've really had a great time making and playing with your Zx81+38 design!
Also, I designed my own take on the TZXDuino, but mine is stripped to a minimal system, it doesn't use a display, and has only two keys, next and start. I got 5 PCB's, one I will use a normal socket, for it, so I can plug in the Arduino of the TZXDuino we already use in the museum, to test if my TZXDuino Pico works, with the same software as a normal TZXDuino. If it works I will use another PCB, and solder the same Arduino Nano into another PCB, so that the building height is so low that it will fit INSIDE of a ZX Spectrum 48K, then I will wire two small push buttons to the back of the spectrum, as wire audio directly to the inside cassette input, and to 5V. So the worker for the museum can just enter CLOAD"" and enter and plug the play button on the back and a game (default is MANIC MINER) will be loaded while he does other work, like starting a MSX2 or the C64 and Amiga 500 we also have in our museum. The TZXDuino Pico is also a GitHub project you can download for free.
These screen tearing artifacts are caused by poor voltage filtering by the 5V regulator (LM7805) which is overheating. I removed them by unwinding 10 turns of the secondary winding of the transformer in the power supply from the transformer. It is also good to replace the heat sink plate with a larger one and stick the heat sink on the ULA. After such a modification, my ZX81 has been working flawlessly for years.
Te artefakty szarpiące ekran są spowodowane złym filtrowaniem napięcia przez stabilizator 5V (LM7805), który się przegrzewa. Ja usunąłem je poprzez odwinięcie z transformatora 10 zwojów uzwojenia wtórnego transformatora w zasilaczu. Dobrze jest też wymienić blaszkę radiatora na większą oraz nakleić na ULA radiatorek. Po takiej przeróbce Mój ZX81 działa od lat bez zarzutu.
Greetings from Poland - the most free and beautiful country in the world
On the original ZX81 of course...
@@kubuspuchatek4730 yes, my ZX81+38 is powered by the ubiquitous USB adapter, so it doesn't have or need a LM7805 voltage regulator, good riddance I say. 🙂Also using 74HC logic does wonders for the power consumption so my clone keeps its cool under all circumstances.
I would love to build a zx81... I think it is a weird but cool computer but I cant seem to find a simple bill of materials and I don't have a 3d printer... I don't know why it has to be so difficult.
Hi Rick, it is a nice build but not like getting a kit with everything labelled 😞. The bill of material for the electronic components are on the designers GitHub page github.com/mahjongg2/ZX81plus38 - ZX81plus38_BOM_revision 1.9.ods It will open in Excel or Libre Office. There are part codes for Farnell in the BOM, but I ended up sourcing from a few suppliers dues to out of stock components. I thought I'd try a 3D printed design as I want to learn a bit more in this area, but someone I know is also making a wooden case to be more in keeping with home brew machines of the late 70s and 80s.
Sounds like the issue I had with my Harlequin 48K I'm building, as I bought just the PCB from Ebay, but when it came, it had no markings on it as to parts. I found the schematics online, but still no BOM, so I had to sit there making a BOM from the schematics!!
Copper fill should be connected to ground. Its not a good idea to leave it floating.