KV21MB - KV21ME - KV21SB - KV21SE SERIES Sony TRINTRON TVs NO SWITCH-ON. STANDBY LIGHT BLINKS TWO TIMES
Two blinks of standby light with this model Sony sets indicates B+ over voltage. That is, 130VDC from the secondary winding of the SMPS transformer supplied to LOT [Line Output Trnsfomer, or Flyback Transformer] has exceeded the predetermined 130 VDC, by some other fault to power regulator section.
Before doing anything, just check for any loose soldering points on the power supply regulator section. Check all the soldering of Hi-Watt resistors, which will heat up during working. Repeated heating and cooling may make its solder terminals to get loose contacted. Normally, these loose contacts are very difficult to detect without the help a magnifying glass. Best to do is, to resolder all suspected solder points by applying a little more solder, without making any solder bridge short in between adjacent solder terminals. There will be very close solder points, which can be make shorted when we resolder them. Take so much care when you do this, as this is the main power regulator section, and if any short when we resolder, will make damage to regulator devices fitted with.
Resolder all the 8 solder terminals of [T604] first. Resolder all the 5 solder terminals of [IC601; power converter]. Check the solder terminals of this IC. The main chance for poor power regulation may lie with the loose solder points to this power converter IC. It will heat up considerably more than any other component, as it dissipates much power by it while it works.
It is advised to replace the error amplifier IC too [IC602 –UPC1093J-I-T]. This is the IC that controls the regulated output voltage. It is a three solder terminal IC, usually look like a transistor. Replace electrolytic capacitor [C646 – I0UF 450V]. Replace the Zener diode [D637 – 6.2V]. In most cases these must solve the problem.
Check the voltage at [TP600] with respect to negative. In short, check the voltage across [C634]. This is the main 130VDC rail that feeds the LOT of the set. This voltage is generated between winding terminals 14 & 15 of T603.
