ZX Spectrum defect causes and repair solutions

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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.