Sinclair ZX Spectrum+ Main Logic Board Part Number

This article identifies the specific hardware revision used in the Sinclair ZX Spectrum+ computer, clarifying the identification system used by the manufacturer. It explains the primary PCB issue numbers associated with the model, details the differences between early and late production runs, and provides essential context for collectors and repair technicians seeking the correct motherboard specification.

When identifying the main logic board for the Sinclair ZX Spectrum+, it is important to understand that Sinclair Research did not use a traditional commercial part number system for internal components like modern manufacturers. Instead, the specific identifier for the main logic board is the PCB Issue Number printed directly on the circuit board. For the ZX Spectrum+, the specific board revision most commonly associated with the model is the Issue 4 board. Later production runs of the Spectrum+ utilized the Issue 5 board. These issue numbers serve as the functional part number for identification, replacement, and compatibility purposes within the retro computing community.

The ZX Spectrum+ was released in 1984 as an updated version of the original ZX Spectrum 48K. While the external case and keyboard were significantly redesigned to improve reliability, the internal electronics remained largely consistent with the final revisions of the original model. The Issue 4 board was the standard fitment for the launch of the Spectrum+. It featured improvements over the earlier Issue 1, 2, and 3 boards found in the original black computers, specifically regarding power regulation and video signal stability.

Identifying the correct board is crucial for restoration projects. The Issue number is typically silk-screened in white text on the green or blue PCB, often located near the edge of the board or between the chip sockets. While some spare parts catalogs from the era may have referenced internal assembly codes, the Issue 4 and Issue 5 designations are the universally accepted identifiers. Technicians looking for a replacement logic board for a ZX Spectrum+ should search for these specific issue numbers rather than a numeric SKU, as this ensures compatibility with the case, keyboard membrane, and power supply specifications unique to the Plus model.