Keyboard doesn’t respond
Step-by-step diagnosis for the ZX Spectrum 48K Issue 2 board. Each step lights up the signal or chip to measure in the explorer below.
No key works, or just one row or one column fails.
- KB1 · KBShow on board →
The membrane
In most cases it is the membrane: the tails crack near the connectors. Check the continuity of every track on the tail before touching the board.
- A8Show on board →
The rows
The eight keyboard rows are scanned through address lines A8 to A15, via diodes. A whole dead row points to that line’s diode or track.
- IC1 · ULAShow on board →
The columns
The five columns go straight into the ULA. If a whole column fails with a good membrane, check the resistors on those lines and the ULA.
Didn't fix it?
We repair these boards on our bench in Loures. The request already includes the board and the fault.
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