Sony KV-13FS100 Product & Training Manual page 33

Oscilloscope
Settings:
0.5V
0.2 s
µ
IK Feedback
Pulses
IK Feedback Pulses in Vertical Blanking (CN301/Pin 2)
Troubleshooting
NOTE: Presently the IK-AKB circuit Video Blanking and Standby/Timer LED 5 flash sequence indication functions
have been bypassed in this first version of the One Chip (IC001). Instead, the video is passed to the CRT so
that any problem in the IK-AKB circuit can be viewed. The problems described below can be quickly diagnosed
by observing the condition of the video present on the CRT and the voltages as described can be used to confirm
a defect.
The IK-AKB circuit indication function as described in the service manual will be implemented in the second
version of IC001.
The following three possible IK-AKB circuit failures and the circuit operation descriptions during these failures
are for the present first version IK-AKB circuit. These descriptions will apply to the second version of IC001
except for: 1) the Video will be Blanked; and 2) the Standby/Timer LED will flash in groups of five in the
second version IC001.
Failures and Circuit/Unit Operation During Failure:
1) Failure: The picture tube is old (one or more cathodes are weak) and the amplitude of the IK feedback pulses
is too low to perform automatic cathode adjustment (Replace Picture Tube).
Circuit Operation: If the IK-AKB circuit cannot compensate for the weakened state of the cathode, video can
still be viewed on the CRT with the defective cathode color missing. To confirm that the tube is defective,
check the voltages on the individual cathodes.
In normal operation with video (color bars) applied, the voltages at the cathodes should be as follows:
KR = 150V
KG = 150V
KB = 150V
Oscilloscope
Settings:
0.2V
2 s
µ
CRT Drive
Pulse
Waveform 6-7
IK Pulses to CRTs (IC001/Pins 31, 33 & 35)
Waveform 6-6
31
6. Video/RGB
Closeup of IK Feedback Pulses
Waveform 6-8