NO PICUTRE; SOUND OK; BLACK SCREEN - Troubleshooting
Check the voltages at CRG socket pins [8. 9 & 10]. If these voltages are found high (almost equal to video output supply voltage 200VDC], the chroma IC should be suspected. Check the voltages at pins 1,2&3 of CN703. These are the red, green and blue color information comes from the main board. There must be a voltage equal to [2.5VDC]. This voltage will vary according to the video information. If this voltage is high, you will get a full white raster with vertical retrace lines all along the screen. if the volte is very low, or no voltage at all, a full black screen will be the result. Never consider this as a simple and easy to do work, as it needs so many checks at various points.
If there is no voltage at these points, or very low voltage than normal; say about 0.03VDC or so, go to chroma section at the main A board, and check the voltages at the pins of the chroma IC. Chroma IC used here in these models are [TDA 8844 N2].
Details about further check with chorma section will be detailed in next post.
