If you don't want to burn your own EPROMs, you can purchase ready-made diagnostic cartridges that plug directly into the expansion port: brendanalford/zx-diagnostics - GitHub
Without a test ROM or tape image, you are flying blind. You might replace a working LM1889 video chip when the real problem is a single bad 4116 DRAM.
This report outlines the primary diagnostic and test programs available for the Sinclair ZX Spectrum
Search for zx-diagnostics on GitHub. This is the official, open-source repository where you can download the latest .rom and .bin files for standard 48K, 128K, +2, and +3 models. zx spectrum test program link
If you are struggling with a specific issue, like a "black screen of death," let me know: you are working on (48K, +2positive 2 +3positive 3
Once your test program link is established and running, follow this workflow to interpret the results: Step 1: Check the Power Rails
Verify the health of the ROM chip and the Z80 processor. If you don't want to burn your own
Diagnostic programs and custom test ROMs bypass the standard boot sequence. They interact directly with the hardware to test:
By using these specialized test links and programs, you can take the guesswork out of soldering and target the exact components needing replacement.
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). This is the official, open-source repository where you
: An open-source diagnostic project specifically designed to help troubleshoot faulty hardware components through a series of automated tests. Writing Your Own Test Program
This is widely considered the gold standard for hardware diagnostics. Because it is an alternative ROM, it does not require working system RAM to boot. If your Spectrum has a completely black screen, you can burn this software to an EEPROM or use a ROM cartridge interface (like the Dandanator or a DivMMC) to force it to run.
You have your link. You downloaded zx-tester-v23.tap . Now what?
: Checking the functionality of the "dead-flesh" rubber keyboard and attached peripherals like joysticks.
Sound synthesis, color generation, keyboard matrix continuity, and basic tape head alignment. 3. Essential ZX Spectrum Test Program Link Resources