Sinclair ZX Spectrum Service Manual

Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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6.3 CORRUPT PAPER, AFTER ULA CHANGE
6.3.1 Initial Check
Check IC1 socket
Check PWR socket is not intermittent
Check IC1 pin 14 for +5V with no discernable ripple
6.3.2 No 3MHz at IC2 pin 6
Low amplitude - check R25
Check TR3
Check IC1 pin 32 for 3MHz
Check IC1 pin 39 for 14MHz
Check crystal X1
Check IC1 pin 13 for +3V
6.4 VIDEO INCORRECT
6.4.1 Dark Screen
Check tuning
Change modulator
6.4.2 Dim ‘Sinclair’ logo
Check +12V
Check C65 for high impedance
Check R52
Check +5V on IC14 pin 3
6.4.3 Wavy lines across screen
Press down on each electrolytic capacitor to see if lines disappear. If so change that capacitor
Check crystal X2
Check/change TR1 and/or TR2
Check/change IC14
6.4.4 Self-resetting
Check TR6
6.4.5 Random dynamic squares
Change C54
Paper area too low
Change IC1
6.4.6 Diagonal lines in the border area
Change R47

Sinclair ZX Spectrum Specifications

General

Brand	Sinclair
Model	ZX Spectrum
Category	Desktop
Language	English