Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Sony KV-32XBR48 picture blinks on and off
Hello all -- I have a Sony KV-32XBR48 that was manufactured in October, 1997. The problem is that the picture blinks on and off at about a one second rate. The audio is constant, and the problem happens whether the video source is from the tuner or a video input. One other symptom is that it seems to me that the time for the picture to come on the first time is much longer than it used to be, and when the picture first comes on, it only stays on for a brief time, and stays off for quite a while. As the set warms up, it gets to about one second on, and one second off. I have spent a fair amount of time looking at the set, and what I see is that the video signal looks good going into IC351 which is a Sony CXA2025 Y chroma/jungle IC. The RGB video drive signals out of this chip change directly as the picture blinks on and off. One other thing is that pin 26 of this same chip changes with the picture blinking on and off. This seems to make sense since it appears to be essentially a flyback transformer current sense. Both the picture on and picture off voltages at pin 26 are much higher than the schematic from SAMS indicates it should be. The only way I see for the voltage to get lower is to draw more current through the flyback. The voltage I see is about 9 volts when the picture is off, and about 8 volts when the picture is on. (I can get more precise readings if that is helpful.) The SAMS predicted voltage at that point is 1.6 volts. I have checked power supply voltages, and they seem reasonable. None of them fluctuates with the picture on/off. I have resoldered the joints at the flyback transformer, but no others. Any tips at this point would be greatly appreciated. Thanks in advance Dave Miller Tucson, AZ |