"Дельта-С" - soviet ZX Spectrum clone
In honor of late sir Clive I present you with this little machine. Although it's not an official Sinclair device, it's a pretty nice and accurate soviet clone of original 48k. It even says "Sinclair Research Ltd" on boot! This is my first computer from autumn of 1991, when my father made me an early birthday present. The state of the case shows some wear, but I am reluctant to paint it, better for it to show some battle scars.
The manual in the video is original, with my markings on it from childhood. So is the tape recorder - "Электроника 302-1", a real piece of crap, but I am amazed that is STILL holds up. I have to replace the belts some day, that's for sure.
Somewhere around 2005 it stopped working and was sent to the attic. In 2013 I retrieved it and tried to power it up - it didn't work. I was going to fix it someday, but kept putting it up and up and up. But this year I finally decided to do it. The problem was with the ROM, particularly with soviet К573РФ4Б chip. It was in a panel and didn't make good contact. The chip itself was also semi-broken, I managed to dump the ROM on a tenth attempt. The second chip - ST M2764AF1 - was kinda broken too, so I replaced it too. I put both new chips in new sockets, and also de-oxided external connectors and replaced the capacitor.
And then the real fun part started. I decided to do an official I/O connector for the peripherals. There are a lot of interesting peripherals for Spectrum now, divIDE or ZX-HD and many more. All the time I've owned this machine I was puzzled by it's expansion port. It's a crazy 96-pin gold-plated "СНП59-96В-23-1" connector, male version. All my life I have never ever seen one of those, as they all were scraped for gold during the 90s. But now there are a lot of websites where you can buy almost everything, so a little googling and I have four (!) on СНП-96 female connectors for my experiments. As for the signals in the connector - there is a pinout in the manual (of course with several mistakes, how could it not be!? It's Soviet Manual, it's main purpose was to confuse the enemy!), and I've found the pinout of the original Spectrum. I looked it up, and the signals looked alike! Address and data buses are easily identifiable, "ЗАПРШ" it's probably "Запрос шины", "Bus Request", "BUSRQ". "НПР" - non-masked interrupt, "NMI"! A little fiddling with two spreadsheets in excel made it possible to make a make connections between all the signals, and from there I could design a simple adapter board from the СНП to the edge connector, as on the original machine. Some chinese PCB factory made the boards for 15 bucks. A little soldering and behold! - the "USSR-Great Britain" adapter is ready. And it works, and at first attempt! Both divIDE and ZX-HD are working fine, even at the same time! So now I can use a normal monitor and load tapes from CF-card. A dream come true and a great finish for the restoration.
There are photos of this machine here:
https://imgur.com/a/kxDLvpY