Load the program using a standard ZX Spectrum interface (like an SD-card based DivMMC). Alternative Way to Play (No Test Needed)
Depending on the state of your ZX Spectrum, you have three primary methods to link a test program to your machine.
Traces crack over time, causing entire rows or columns of keys to stop responding.
The firmware is available for download on the project's GitHub releases page. Look for the testrom.bin file in the latest release package. zx spectrum test program link
For every hobbyist staring at a black screen, wondering if their cherished childhood computer is now a doorstop, the test link offers hope. It isolates the fault. It transforms a vague problem ("it doesn't work") into a solvable puzzle ("bit 4 of the upper memory is stuck high").
If all lower RAM fails, check the multiplexer chips (74LS157 or 74LS257). Step 3: Run the Sound and Color Cycle
While modern PCs have built-in BIOS self-tests, the ZX Spectrum had very little self-awareness. If the Z80 CPU was functional, the machine would try to boot. If the ULA (Uncommitted Logic Array) was failing, or the DRAM was corrupted, the user was often greeted with the infamous "black screen of death" or random attribute artifacts. Load the program using a standard ZX Spectrum
Visit worldofspectrum.org or spectrumcomputing.co.uk and look in the utilities section for "Test Tape" or "Diagnostic".
Install the diagnostic chip into the ROM socket of the Spectrum. Upon powering on, the screen will display a detailed map of working and failed RAM chips.
Disclaimer: Repairing vintage electronics requires soldering skills. Always power down the unit before attempting repairs. If you'd like, I can: The firmware is available for download on the
The , specifically the version published by Sinclair Research Ltd in 1985, is a legacy utility designed for internal diagnostics and Input/Output (I/O) handling on the 48K ZX Spectrum. Overview & Utility
A is the most valuable bookmark you can have if you own more than one Speccy. The link provided in this article ( github.com/retrobreww/zx-diag ) has been tested on Issue 2, Issue 3B, and +2 Grey models as of December 2025.
The Spectrum’s ULA (an early gate array) is responsible for generating the video signal and handling RAM contention with the CPU. The test program checks the ULA by writing patterns to the screen memory area ( 0x4000 to 0x57FF in a 48K model).
Let me know how you'd like to proceed with your troubleshooting! Test Program - World of Spectrum