Sinclair ZX Spectrum

I got this machine from an online auction in February 2022. It was sold as partially working, but with strange pixel artifacts in the display output. When I tried it after purchase, I only got a black picture with a white border though. A voltage check showed that the DC converter was broken because of a shorted coil. After rewinding the coil and replacing the usual power related semiconductors, the machine was working again.

The component date codes of this Speccy tell an interesting history. This machine was built in 1982, probably as 16K model. All components that are related to the 48K memory are socketed and have a 1983 date code, so the machine was probably extended to 48K in that year. As the only chip, the ULA has a 1984 date code. Maybe the original ULA got broken and was replaced in that year.

An important configuration jumper was missing. I have serious doubts that this machine was ever running stable after it became its 48K upgrade.

On the outside this Spectrum is in a suprisingly well, almost mint optical condition!

Configuration

• Built: 1982
• Mainboard: Issue Two
• CPU: Z80A
• ULA: 6C001E-7 (date code 8418, probably made in Phillipines)
• RAM: 48KB
• Composite mod

Restauration Works

• Restauration was carried out in February 2022
• Removed an overly complicated composite mod made by the previous owner, and just did the classic composite mod (reversible).
• Repaired a coil damage: Wound new coil, preemptively replaced TR4, TR5, D16
• Replaced 7805 with Traco Power TSR-1 DC/DC converter, removed heatsink
• Calibrated video output