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A replacement sound chip for the Commodore 64. You must be SIDding!

This is a replacement board assembly for the SID chip in the Commodore 64 and 128 computers.

The original SID chips are not the most robust of integrated circuits, and in this C64, it faded away until it could barely be heard. Replacement, original chips are becoming hard to find and they tend to be quite expensive, plus there's always the risk that they will be ageing badly too.

A SID sound chip

Good old SID
(1987 vintage from the date code)

Over the years various microcontroller-based replacements have been developed. The SIDKickPico, by Frenetic, is the new kid on the block. It's based on the Raspberry Pi Pico board attached to a carrier PCB with some interface logic. Assembling a completed unit is fairly straightforward, and for this project I have been assisting with code testing, notably for the analogue joystick/paddle logic.

SIDKick Assembly

SIDKick Assembly in Commodore 64

SIDKick Setup Menu

Project details are here: https://github.com/frntc/SIDKick-pico

 

Retro electronics - RGBS to Composite video conversion

I decided I wanted to have a go at interfacing some of my retro kit to a Teletext (Ceefax) adapter and found "The Teletext Experimenter’s Board" by Oddbloke Geek. This board uses the SAA5246AP Teletext processing chip, so I bought a couple of those and am planning to build my own circuit. One addition I want to make is a composite output; the 5246 only outputs RGBS.

There's a number of classic converter chips from the 80s and 90s; parts such as the AD723, AD724, CXA2075M and MB3516A. All these chips are still available, although the AD72x ones are getting relatively expensive. 

While searching for options, I came across this reversing camera CAN bus module on AliExpress - it's an RGB to composite converter, and works out at £11 shipped, so I bought one.

Inside is a neat RGBS-to-Composite (NTSC) converter board, which I will remove and repurpose, plus there's the bonus of a project box + connectors for something later! This board uses yet another different chip - the KA2198BD. This chip and the CXA2075M and MB3516A are broadly pin compatible and interchangeable.

I've yet to hook up the board, but it looks like it will do the trick, and will save some time sourcing individual components and building a circuit.

Now I just need to find the time to work on the teletext portion, and then see how to hook it up to something such as a Raspberry Pi or retro computer.

RGB to Composite converter module from AliExpress RGB to Composite converter module from AliExpress - opened

RGB to Composite converter module from AliExpress - close up of circuit board

 

The Multicomper

The Multicomper is a motherboard for the EP2C5T144C8N Cyclone II FPGA dev board, modelled on the "Multicomp" functional computer design spec by Grant Searle.

Grant has written up the circuit design notes together with the instructions to turn it into one of a number of computer emulations, including the original UK101, but there was no accompanying PCB design. A few others have designed "Multicomp" baords, and here's mine!

Multicomp PCB

Full notes and more images can be found at: https://github.com/linker3000/Multicomper

Oh, hello

I don't blog much,. but when I do it'll be here!

 

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