Zx Spectrum Test Program Link Upd «1080p»

If the video was completely dead, the program would communicate through the beeper . A series of long and short beeps (a binary code) would tell you the exact fault—like a morse code for motherboard repair.

If you are trying to test a "Link" (a connection to an external drive or SD card): zx spectrum test program link

High-level steps to build such a program: If the video was completely dead, the program

Open-source and constantly updated. It's often bundled with modern diagnostic cartridges. If the video was completely dead

Diagnostic programs feature a "Keyboard Map." If an entire diagonal line of keys doesn't work, it’s usually the membrane, not the software.

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