Roland SP-404 restoration

I found this original Roland SP-404 on Vinted for €110. It was listed as partly working: the description said it only worked on batteries.

I repaired the solder joints on the board and tried it with the correct power supply. The sampler powered up and worked properly.

Cosmetic clean-up

The faceplate was scratched, so I polished it to bring it back up. The original knobs were old and ruined, so I bought a replacement set.

• Replacement knobs

I also cleaned the circuits with this circuit cleaner.

The faceplate template

The biggest focus of this restoration has been creating a faceplate template. I couldn’t find a usable template online, so I made one for this SP-404 myself. The template is now available in Resources; I’ll add the finished faceplate there when it’s ready.

Download the faceplate template ↓

Browse Resources ↗

Custom firmware experiment

I also explored making custom firmware. This part was AI-assisted vibe coding: I used AI to help write and iterate on a small firmware patching tool and a test build.

I figured out the simple 16-bit checksum used by the official update files and verified my checksum tool against three official firmware builds. The test build only changes the displayed version string to 1.06. It does not add any new features, so this is an experiment rather than a finished custom firmware release.

I have not yet flashed the test build on the sampler or proven that I can recover it by reinstalling official firmware. The recovery path still needs to be tested on the unit.