ZX Spectrum 48K any board issue in Plus case
Symptom: Symbol Shift – A does not result in ‘STOP’ (‘Stop key doesn’t work’)
Solder a 22K resistor over R68.
ZX Spectrum 48K issue 6A
Symptom: 12V = +/- 8V
Replaced TR4 & TR5: 12V is now 26V!
Replaced capacitors and detached 12V from 4116 chips: 12V is now 11V
Found one defective 4116 chip by reconnecting 12V one at a time.
ZX Spectrum 48K iussue 6A
Symptom: random crashes, beeper error tone from time to time, unstable.
Paul Farrow’s diag ROM cartridge didn’t detect an error, but Brendan Alfords RAM tester (loaded from SD card by DivMMC EnJOY! *mini*) detected a fault in IC18.
ZX Spectrum 48K iussue 3B
Symptom: loading errors from DivMMC, not from DivIDE.
Replaced CPU with NEC.