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Sony TV model KV-21TSR1 with Arcing and No Raster Problem


I am having a home service to a Sony TV model KV-21TSR1 with a complain of having a loud noise coming inside the unit that looks like the tube is going to break. I suspect that the FBT (flyback transformer) is the main cause of the problem for having a leak maybe on its high voltage so I opened the unit and checked immediately the FBT and then I found out that it has a cracked on the body of the FBT. So I take out the FBT from the board by desoldering the lead using a desoldering pump then I tell the owner to buy a new one but it is hard to find an original one so as a replacement, a locally made is used but it won’t assure it can take to a long run.

Sony TV model KV-21TSR1

And then I continue repairing the unit and put in the board my newly brought FBT and monitored the B+ supply and another problem came out. It has no raster and then I checked the G2 and it measured 500V which is a correct voltage and the heater also glows and it measures 3VAC which means the heater is ok. And I measure also the RGB on the CRT socket and it measures 180V which is a signed that the ABL section is not functioning. Then I checked next the ABL circuit for this unit because we all know that an opened resistors in an ABL circuit can cause a no raster problem.

I check the two resistors connected in series near the FBT that is connected from B+, up0n checking I f0und out that the two resistor in series are open. Here are the resistors:

r816=33k 1/8 watt
r857=31k 1/8 watt

Then my another problem is that, I only have 33k resistor but I dont have 31k resistor, so I searched for a solution for this problem. I found three 10k resistors on my stocked components and one 1k resistor that I connect in series so  I can get the value of of 31k resistor. Then I put on the board the resistors then solder and testing. Viola, the raster came out and works fine. Job well done.

Posted by Ronelex 0 Responses

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