Help needed for Troubleshooting Sony KV-G21B1

[Ech]

Hello all ..,
I got an Sony Crt Tv (model number - KV-G21B1) and i found its damper diode is short. Then, I replaced it with a new diode (with same number as the old one) and after trying to turn on the Tv, the indicator led turns On and Off continuously with all the voltages of the board turning On and Off repeatedly. Then I found that the new damper diode I replaced was also short. I tried with few diodes but all of them became defective. I couldn't find the reason behind damaging the damper diode repeatedly and the following are the things I did with the TV board.

• Resoldered all the dry joints including the Neck Card.
• I found the 33v zenar diode is short at tuner and replaced it.
• All the suspicious mylar capacitors are replaced around the H-OUT section.
• Replaced the flyback transformer but nothing changed.
• I checked the HOUT and VOUT transistors and they are fine.

Outputs of the chopper transformer are 115V and 15V. The flyback gets 115V properly.
Please support me to solve this problem and I am clueless in this case to repair this Tv.
Thank You very much for your time.

 

[bertus]

Hello,

When the powersupply is constantly switching on and off (hicking) , there must be an overload on the power supply.

Bertus

 

[Ech]

Hello,

When the powersupply is constantly switching on and off (hicking) , there must be an overload on the power supply.

Bertus

Hello Bertus ,
Thank you very much for your advice.
In the power supply section what I noticed is there are three 15 KΩ, 2W resistors which are in series directly with the positive lead of the smoothing capacitor to power up the Vcc pin of the STR S6707, are extremely hot even if the Tv in standby mode for very few seconds. Then I removed the STR and powered up and I noticed that again those resistors have become extremely hot. Is that can be a problem for this case or what can be causing the for the overload problem? I tested these resistors with a multimeter and found that they are fine.