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Sony TV model KDP-57WS655 that will not turn on    
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shu7241



Joined: 16 Feb 2009
Posts: 1

PostPosted: Mon Feb 16, 2009 6:27 am    Post subject: Sony TV model KDP-57WS655 that will not turn on Reply with quote

Have a Sony TV model KDP-57WS655 that will not turn on. After turning tv on and getting nothing, I can get it to come on by constantly unplugging and replugging, usually 3 or 4 times, until I hear a distinct click that appears to come from the back, right corner of the tv. When I hear the click, then I know the tv is on. TV stays on and has no other problems. TV is 4 years old. Indicator light blinks 9 times when not working. If anyone has an answer, can someone who is fairly good at fixing things fix this problem or will I need a tv serviceman. Thanks very much for any help. Bill
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Jesse Mack



Joined: 22 May 2008
Posts: 600
Location: The Last Frontier

PostPosted: Mon Feb 16, 2009 2:22 pm    Post subject: Reply with quote

Bill,

I have checked and the board is no longer available for a board level repair, This is a nasty little problem that must be troubleshot with a "O"scope. It is caused by a noise pulse or shorted component in the zerocross Detect circuit of the G board. Q605, D690, D647 and IC001 Micro have all been known to cause this problem. These are the components on a direct view set (not yours) but the symptom and placement is the same, However, the schematic ID's are different. The parts D6301, D6309 and D6116 diodes for your set have been known to cause this problem. Be aware that the components are rarely shorted and cannot be checked effectively with a multimeter. Usually the components are simply noisy causing a noise pulse to appear on the waveform which will shut you set down with 9 blinks.

The circuit is called a zero cross detector, and the purpose for it is to detect when the AC line is crossing zero volts and to synchronize the main relay closure with the cross by zero of the AC line. In the process of charging the capacitors (C621 & C629) the current is quite large, and this can produce sparking in the relay contact tabs, this sparking will deteriorate the relay through time. The sole purpose is to provide pulses to the microprocessor synchronized with the crossing zero of the AC line waveform.

If you have a "O"scope and a schematic I can walk you through it, However, if you do not, I would advise taking the set to a competent technician.

Hope this helps

Jesse
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