Sinclair Research ZX Spectrum - Page 37

AREA SYMPTOM ACTION
No video, (contd) No VIDEO INPUT at 1. Check waveform at IC14
IC14 pin 12. pin 13. If correct check
TR1 and TR2.
2. Check waveforms at IC1
pins 15, 16 and 17:
If correct check VR1, VR2
(Issue 1 and Issue 2 boards).
3. Change IC1.
4. If +5V and VIDEO INPUT
correct change modulator.
Corrupt Paper, - 1. Check IC1 socket.
after ULA change. 2. Check PWR socket is not
intermittent.
3. Check IC1 pin 14 for +5V
with no discernible
ripple.
No 3 MHz at IC2 1. Low amplitude - check
pin 6. R25.
2. Check TR3.
3. Check IC1 pin 32 for 3
MHz.
4. Check IC1 pin 39 for 14
MHz.
5. Check crystal XI.
6. Check IC1 pin 13 for +3V.