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Old 26th August 2009, 04:26 PM   #11
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Join Date: May 2005
Location: Johannesburg
Hi All

After replacing most of the electrolytics I still had not managed to sort out the problem. I actually went to the point of removing the opto isolator and then noticed that the voltage immediately on switch on went up to 250V on the 142V output connected to a 656ohm/80W load (not connected to the Main board) This cleared up the possibility of a faulty transformer. You will never believe what the actual culprit was. R810 is a 0.27ohm resistor and showed no signs of being burnt or cracked and I removed it completely from the board and measured it. It turned out to be 5.1ohms Go figure!

In any event I replaced this resistor and voila everything came back to normal. The TV is now sorted out and has been running well for the last 5 days.

The lesson I learnt from this experience is that even though something looks to be in perfect condition it might not be.
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Old 26th August 2009, 09:59 PM   #12
star882 is offline star882  United States
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If a resistor is repeatedly cycled to or near its ratings, internal cracks may form that result in intermittent faults and increased resistance. The fix is to replace it with one a size larger.
"Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!
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