This Avant 100 Hz Chassis 83/00 is giving me a headache. It is hardly
to service due to the complexity of wiring interconnecting all the
different PCB's.
The problem is very simple:
Set switches on flawlessly
There is Sound, and programs can be selected, but:
There is no video picture
The CRT shows a blank raster with pronounced retrace lines which
cannot be removed completely by readjusting the CRT G2 voltage.
Probing the video processor IC TDA 4780 learned that there is video
INPUT available but NO RGB output can be seen on the oscilloscope. So
as a first approach the IC was replaced by a new one.
Results after replacement identical. Checking the pin-out voltages
learned that ALL showed logical results, except for RGB feedback at
pin? reading low (2VDC ilo 5 VDC)
I hope one of the guys out here can shed some light on my problem box
which is fortunately fully covered with its service documentation....
TY
Brasto