SECTION 4.3 - FAULT DIAGNOSIS AND REPAIR
LIST OF CONTENTS
TV screen dead, smoke appears on switch-on /
Not Initializing
No Video
Corrupt Paper, after ULA change
Video Incorrect
Colour Tuning Faults (Issue 1 and Issue 2
boards)
Colour Faults (Issue 1 - Issue 3 boards)
Keyboard Faults
Regulator Coil
Speaker
Speaker Load Input Waveforms
TR4 base-collector shorted | Remove TR4 |
Short persists with TR4 removed | |
TR4 blows again |
No video | |
No video after ULA changed | |
No +5V input | |
No VIDEO INPUT at IC14 pin 12 |
|
Initial Check | |
No 3MHz at IC2 pin 6 |
KB1 fault | |
KB2 fault | |
Dead keyboard | Change IC1 |
Wrong keyboard response | Change IC1 |
Keyboard response too fast | Change IC1 |
Coil excessively noise | Change coil |
No speaker output |