What is the computer currently showing? (e.g., black screen, garbage patterns, tape loading errors)
ULA chip is failing or overheating. Consider a vLA81 replacement.
The additional 32KB (in 48K models) or banked memory (in 128K models). zx spectrum test program link
The 48K Spectrum uses 16 64kbit DRAM chips (4164 or equivalent). These chips are notorious for failure due to timing sensitivity. The test program runs a multi-pass algorithm:
Clear on-screen text detailing exactly which RAM bit (D0 to D7) has failed. What is the computer currently showing
3. Tape-Based Test Programs (e.g., Sinclair Factory Test Tape)
While official documentation for this specific 1985 release is sparse compared to the 1983 "Test ROM" (which was restricted to official Sinclair Repair Engineers), it typically covers: The additional 32KB (in 48K models) or banked
Download the latest version from Retroleum's website . The firmware is included in the "SMART Card Software" ZIP package. The documentation PDF can be found directly at retroleum.co.uk/diagrom/diagrom.pdf .