Sony HKDV-900 Maintenance Manual page 31

The LED sometimes does not light when the button is pressed
Is input signal (ON : low/OFF : high) at
I0 to I7 of IC309 (G-3) and I0 to I15 of
IC311 (G-3) the CP-364 board stable?
NG
IC309 or IC311 defect on the CP-364 board
or soldering short
The LED lights or blinks before the button is pressed
Is input signal (ON : low/OFF : high) at
I0 to I7 of IC309 (G-3) and I0 to I15 of
IC311 (G-3) on the CP-364 board kept low?
NG
IC309 or IC311 defect on the CP-364 board
or soldering short
The 7SEG LED display does not change even if switch settings of S101-7 and S101-8 are
changed
Are CHROMA signal at pin 9 of IC105 (J-2)
on the CP-364 board and VIDEO signal
(_3 : low/_∞ : high) at pin 8 of IC105
proper?
NG
(The result display is fixed at +5 V)
Switch defect or short in line
(The result display is fixed at ground)
Switch defect, pull-up resistor defect,
or short in line
(The result display is fixed between +5 V and 0 V)
Line disconnection between switch and
IC105 on the CP-364 board
(The result display is unstable)
IC105 defect
HKDV-900
OK
Connection defect of the harness between
CN400 (D-3), CN401 (A-3) on the CP-364
and CN1 (C-1 : B side), CN2 (A-1 : B side)
on the CP-365 boards
OK
Connection defect of the harness between
CN400 (D-3), CN401 (A-3) on the CP-364
and CN1 (C-1 : B side), CN2 (A-1 : B side)
on the CP-365 boards
2-3. Troubleshooting
2-19 (E)