Oli's old stuff

Tinkering with retro and electronics

Sep 20, 2020 - 8 minute read - sinclair electronics retro hardware zx81

ZX81 hardware hacking - Homebrew ZX8-CCB

ZX81 Hardare Hacking - Homebrew ZX8-CCB In my last post I talked about the problems associated with the video signal that the ZX81 outputs. There are various mods that can correct this, with one of the leading ones being the PokeMon ZX8-CCB. In this post I’ll explore a homebrew hack that aims to recreate the ZX8-CCB for fun and educational purposes. DISCLAIMER This is not endorsed or associated with the original ZX8-CCB project in any way.

Sep 19, 2020 - 8 minute read - sinclair electronics retro hardware zx81

ZX81 Video Conditioning Mods

ZX81 Video Conditioning Mods The ZX81 is notorious for outputting an RF signal that modern TVs struggle with. This is a post that explores the video signal from the ZX81 and discusses a few of the mods for improving it. ZX81 Composite Mods Modern TVs have issues with the ZX81 RF signal, and most common solution is for people to modify their ZX81 for composite video out. Knowing nothing about the subject, I rushed out and bought a kit from tfw8bit.

Sep 6, 2020 - 8 minute read - spectrum electronics retro hardware 4116 ram

ZX Spectrum 4116 RAM Replacement Board - Part 2

Building a ZX Spectrum Lower Ram Replacement Board - Part 2 In my last post I talked about the broadboard prototypes of my attempt to build a Lower RAM replacement for the ZX Spectrum. It was encouraging to see that something could work on a breadboard, even if it was glitchy. The long wires and extra capacitance would cause a lot of noise for something that needed to be accessed as frequently as RAM.

Aug 14, 2020 - 7 minute read - spectrum electronics retro hardware 4116 ram

ZX Spectrum 4116 RAM Replacement Board - Part 1

Building a ZX Spectrum Lower Ram Replacement Board - Part 1 As I mentioned in my previous post on messing around with Arduino and 4116 DRAM, the ZX Spectrum is prone to failures of the lower RAM. Many people (myself included) choose to replace a failed 4116 RAM chip with a modern replacement “board” that uses SRAM instead of DRAM. The reasons are clear, modern boards are made using readily available components - even “new” 4116 chips are all old stock and 30-odd years old.

Jul 23, 2020 - 8 minute read - spectrum electronics kicad retro hardware

Kempston Joystick Interface Stripdown

Kempston Joystick Interface Stripdown One thing you seem to accumulate a lot of when acquiring ZX Spectrums is a variety of peripherals. Joystick interfaces, in particular, are one that seem to turn up tim and time again. I was recently sorting through them to find a working one to send over to @breakintoprog and one I tested was broken. This is a post about me stripping it down and figuring out what makes it tick.

Jul 12, 2020 - 9 minute read - spectrum electronics arduino retro hardware 4116 ram

Arduino and 4116 DRAM

Hardware Projects First blog in a while; I’ve been working away slowly on SMEG but I’ve also been learning how to repair and restore the very hardware I’ve been emulating and writing software for - the humble ZX Spectrum 48K! I’ll talk about some of the repairs another time, but I thought I’d take this opportunity to write about some of the experiments I’ve been performing with the Spectrum’s RAM.