SONY – KV20M - KV20S - Trinitron Color TVs - Standby light Blinks Two Times
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.