35
There is an input for the focus grid at pin 3 G4 of the tube. This input is
from the electrical focus control VR on the FBT. It should be set for opti-
mum focus using a dot pattern.
Pin 1 of the tube CV is used for convergence. A part of the H1 voltage is
input to pin 1 through RV701. The convergence plates in the tube align
the colors to each other using this voltage.
If any of these signals are incorrect or missing, the video may never unblank
at turn ON. This would leave us with a starting point to troubleshoot
blanking problems. Blanking can be caused by faulty IK or tube bias
operation.
Troubleshooting
The first step in troubleshooting is to determine if there is a tube bias
problem or an IK blanking problem. Use of the Self-Diagnostic feature
does not seem to be of any help here. You will know if you are in video
blanking if the Standby/Timer LED flashes continuously or in sequences
of five soon after turn ON.
There should also be HV and sound present.
If no HV is present, the Standby/Timer LED should be flashing in se-
quences of two or four.
If a problem occurs with one of the colors, the set will remain in video
blanking mode. This means no video or OSD will be displayed. However,
the YCJ will continue to output these IK pulses. One possible method for
seeing these lines uses the Service Mode. You can enter Service Mode
by pressing “Display”, “5”, “Vol+”, then “Power”. After the set is ON, press
the “1” button 15 times. This will bring you to the VSIZ adjustment al-
though it will not be indicated on the display. Press the “6” button until the
IK lines are visible. If one of the colors is missing, troubleshoot the path
for that color. If all the colors are missing, you may have a faulty YCJ or
tube bias.
Note: This method is only valid for BA-5 chassis.
See if the YCJ is outputting a pulse for each color. If there is communica-
tion between the YCJ and Syscon, these pulses should be output. Their
amplitude should be between 1 and 4 volts peak to peak. If one of these
pulses is missing at the RGB outputs of the YCJ, replace it. These same
pulses should also be present at the RGB inputs of IC702 on the CB
board.
If the inputs to IC702 CRT Drive are good there should be an output as
shown below. Note it is inverted and much larger.
Summary of Contents for FD TRINITRON WEGA KV-13FM12
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