My standby light comes on and blinks seven times repeatedly but no picture.
Seven blinks of standby light in Sony tv denotes that there is a high voltage problem. It is otherwise called as high voltage shutdown.
Normally 32" tvs has an anode voltage of 27,000Vdc approximately. If it rise beyond its limit, the microcontroler in your set will detect the high voltage, and will prevent it from working further, to protect you fro X-Ray emisson as well as to protect the TVs other components inside the ciircut board from further damages, and will inform you about this fault, by seven continous blinkings of standby light. Now you are seeing this.
The final anode voltage depends very much on the input DC voltage to LOT [Line Output Transformer]. Usually this supply rail will have a voltage level of 135 to 140VDC. If it rises above this level, extra high tension voltage generated by the above said LOT will also rise proportionaly to high, which will goes to the final anode of the picture tube. If this voltage goes very high, there is a chance to radiate X-Rays from the picture tube which will harm you. This high voltage protection also known as X-Ray protection.
The main reason for this fault is related to the regulated power supply section inside the circuit board of your tv. To repair this, you have to open the back cover of your TV. Take every precautions before doing anything to your TV as it is an electrical equipment, which generates high voltages inside it while it is working, and there are voltage points as high as 30KVDC [30,000VDC], wich is very dangerous.
Just open your tv, and locate the power supply section. It is very easy to locate, as the main supply wire goes into it. There will be a regulator Ic, normally Sony sets have STR numbered ICs are used in that section. This regulator will heat up to 75degreeC, and there is a chance to get loose the solderings on its leg points, as continous heating and cooling process. Just look for any loose solderings on the solder side of your TVs power supply section. In practice, I found this in too many Sony sets, during my 36 years in this service field. It is very difficult to detect the exact loose point, so I always do is, just resolder most of the suspected points on the pcb, by applying a little more solder, and will retify the problem. Moreover, just replace small electrolytic capacitors fitted on that board, because some of them may cause this voltage rise. The DC supply voltage rail, will be between 135VDC or so. Any fault in the components fitted around the above said STR will cause this problem. So check every components, and replace if needed. If this does not help replace the STR with same type and number.
Go further with confidence. You can and you will. Wish you sucess. Take care. OK.
Nov 18, 2010 |
Sony FD Trinitron WEGA KV-32HS510 32" TV