tv sony kv27ts35 bug !!!

[chantal4]

Horizontal output and the switching power supply transistor on this tv blew
up. The parts have been changed and each power sections have been checked.
When I tried it, it worked. But when shuting down the tv, the switching
power supply transistor blew up again (2SC4664). I simulated the control and
it's good. I suppose it could be a security capacitor or a diod seek. If
you could give me any advice, tip or electronic map will be appreciated.

thanks

 

[BigMike]

"chantal4" <chantal4@sprint.ca> wrote in message
news:MUqyb.580$gs2.4061@newscontent-01.sprint.ca...

Horizontal output and the switching power supply transistor on this tv
blew
up. The parts have been changed and each power sections have been checked.
When I tried it, it worked. But when shuting down the tv, the switching
power supply transistor blew up again (2SC4664). I simulated the control
and
it's good. I suppose it could be a security capacitor or a diod seek. If
you could give me any advice, tip or electronic map will be appreciated.

Check for bad solder joints on the horizontal driver transformer. Common
problem. When as the horizontal output transistor looses drive from the

transformer, it blows taking the switching transistors with it.

 

[Jerry G.]

If there is no drive to the horizontal output transistor, it will blow
again, thus taking out the power supply transistors, and or drive devices.
This will do it every time, within about 20 ms. You will need to replace
all the parts again.

Service the power supply, and start the set with no horizontal output
transistor inserted. Take a scope and see if there is proper horizontal
drive pulses going to the base of the transistor, during the kick-start
period. There should be start-up pulses for about 100 ms, after the power
is turned on. They will cut out, because at this time there is no
horizontal output. If there are no start-up pulses, trace back via the drive
transformer to see where they stop.

I have had the driver transformers in these sets go faulty. Sometimes I also
had to change the transistor that drives the transformer. I have also had
the lead wires of the transformer go cold solder on me. If there are
proper start-up pulses, then verify that the flyback does not have a short
in it, or something on its secondary side is directly shorted.

Every time you turn on the set with the new parts, and it does not work due
to the horizontal failing, you will have to change the devices again. All
the fault conditions must be found to have the set work properly without
damaging the devices.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"chantal4" <chantal4@sprint.ca> wrote in message
news:MUqyb.580$gs2.4061@newscontent-01.sprint.ca...
Horizontal output and the switching power supply transistor on this tv blew
up. The parts have been changed and each power sections have been checked.
When I tried it, it worked. But when shuting down the tv, the switching
power supply transistor blew up again (2SC4664). I simulated the control and
it's good. I suppose it could be a security capacitor or a diod seek. If
you could give me any advice, tip or electronic map will be appreciated.

thanks

 

[Yvon Laurin]

Try to put ultra high speed zener diode to prevent spurious voltage to
blew up the transistor.
Example: Use two 400 volts zener 5 watts in series to stop the maximum
voltage at the junction of the transistor to 800 volts.
I have made this to a monitor that use to burst the transistor 3 times
and never made it again 5 years.

Be sure to match the transistor rating to prevent being too low or high
in the switching range.

Good luck !!


BigMike wrote:

"chantal4" <chantal4@sprint.ca> wrote in message
news:MUqyb.580$gs2.4061@newscontent-01.sprint.ca...

Horizontal output and the switching power supply transistor on this tv

blew

up. The parts have been changed and each power sections have been checked.
When I tried it, it worked. But when shuting down the tv, the switching
power supply transistor blew up again (2SC4664). I simulated the control

and

it's good. I suppose it could be a security capacitor or a diod seek. If
you could give me any advice, tip or electronic map will be appreciated.

Check for bad solder joints on the horizontal driver transformer. Common

problem. When as the horizontal output transistor looses drive from the
transformer, it blows taking the switching transistors with it.