NO PICTURE. SOUND OK. SONY [KV-HA & KV-HW VEGA SERIES TRINITRON TVs]
Check the voltages at pins 1, 2 & 3 of (CN 703), at video amplifier card [picture tube base card]. If found abnormal, or less than 0.5VDC or so, the chroma IC on the A board should be suspected. But before making it sure, just check the voltages at the video output pins [Pin 19, 20 & 21] of IC TDA 8844/N2. It should be around 3VDC or so. If there is no voltage at all, check the 9VDC bus from the SMPS power supply. This voltage comes out from a controlled regulator. Check the voltage at the cathode of D314. Must be 9VDC. If not, check the voltage at its anode. If there is no voltage at the anode of this diode, make sure that the controlled regulator is not working. May be damaged or 9V regulator IC has damaged or not switching ON by the system control. If there is 9VDC at the cathode of D314, then check the voltage at pin number 37 of TDA 8844/N2. If there is no voltage, check L312 for open circuit. If these voltages are OK and still there is no voltage at the video output pins of the chroma IC TDA8844/N2, check the voltage at Pin number 7 & 8 [Serial Clock and Serial data respectively]. They should measure about 4.6VDC. These voltages are comes to chroma IC from system control IC If there is no voltage at these pins, leave the chroma section, and come towards main system control section [IC CXP85***].
If serial data and serial clock voltages are OK, and there is 9VDC at pins 37&12 of TDA 8844/N2, and still there is no voltages at the video output pins stated above, touch the top of the main chroma IC TDA8844/N2, and feel the heat generated by it. It can be moderately heated, but not overheated. If it overheats, while all the above said voltages are ok, there is no further checking needed. The IC is defective, and should be replaced.