Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

Good diagnosis.
"Max" wrote in message
...
Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

A scope and basic troubleshooting...

Leonard

"Max" wrote in message
...
Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

On Wed, 05 Oct 2005 23:03:52 -0700, Max wrote:

Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

The light bulb trick would have saved the HOT...they don't short for
no reason...this thing, if memory serves, requires a multiple-step
troubleshooting procedure that I don't recall, the ability to vary
line AC input, etc...if you can't find the correct procedure, and
don't have the gear, take it to a shop that can repair it.

Tom

"Max" wrote in message
...
Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks


First thing I'd check are electrolytic capacitors, Sony sets that are
blowing parts can be a real pain to fix, they're good units but very touchy
in some respects and have to be fixed just right.

James Sweet wrote:
"Max" wrote in message
...

Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks



First thing I'd check are electrolytic capacitors, Sony sets that are
blowing parts can be a real pain to fix, they're good units but very touchy
in some respects and have to be fixed just right.


I checked the caps which is involve in B+ line.All good.The TV start
doing HV but for few seconds then Horizontal output transistor blow out
and TV shut down to safe mode.I checked HV by HV meter connected to
anode.Any other suggestions.

PS TO TOM I'm a shop working in this business for 15 years.Fixed
previous models of Sony for 5 minutes especially when 2 blowed out
transistor in power supply and in chain reaction of blowed HO
transistor.I never had the problem like this with Sony that's why asking
people who got similar problem before to safe some time on troubleshooting.

Check the pincushion diodes and the related passive components in the output
stage.

If you can, drive test and ring test the flyback. Also, look at the
collector waveform as you start it up and if it doesn't go directly to a
clean pulse with no ringing, you likely have a bad flyback.

These sets have had bad flybacks and problems in the pin circuits that will
blow outputs.

Leonard

"Max" wrote in message
...
James Sweet wrote:
"Max" wrote in message
...

Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks



First thing I'd check are electrolytic capacitors, Sony sets that are
blowing parts can be a real pain to fix, they're good units but very
touchy
in some respects and have to be fixed just right.


I checked the caps which is involve in B+ line.All good.The TV start doing
HV but for few seconds then Horizontal output transistor blow out and TV
shut down to safe mode.I checked HV by HV meter connected to anode.Any
other suggestions.

PS TO TOM I'm a shop working in this business for 15 years.Fixed previous
models of Sony for 5 minutes especially when 2 blowed out transistor in
power supply and in chain reaction of blowed HO transistor.I never had the
problem like this with Sony that's why asking people who got similar
problem before to safe some time on troubleshooting.

On Wed, 05 Oct 2005 23:03:52 -0700, Max wrote:

Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

Replace any electrolytics in the horizontal drive circuit. Did the
HOT get hot before it failed? If it did, I would suspect a horizontal
drive problem.

It could be a bad flyback, but the bad Sony flybacks I've seen always
caused instant HOT failure.
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005

I have seen quite a few that do not blow the output. Just changed one in a
KV36FV16 that would shut down on trying to start. Rings bad out of circuit,
had ringing on the collector pulse in circuit, and drive tests bad. I have
seen some Sony FBTs that ring good have a clean pulse and only test bad on
the drive tests.

Leonard


"Andy Cuffe" wrote in message
...
On Wed, 05 Oct 2005 23:03:52 -0700, Max wrote:

Hi I trying to fix Sony KV-27FS12 27' TV.Front LED blinking 4 times.I
found short horizontal output transistor D2578.After replaced and try to
turn on TV the transistor blow out again after it start working for few
seconds.There is no bad solder connections on the board.I suspect bad
flyback.Any suggestions?Thanks

Replace any electrolytics in the horizontal drive circuit. Did the
HOT get hot before it failed? If it did, I would suspect a horizontal
drive problem.

It could be a bad flyback, but the bad Sony flybacks I've seen always
caused instant HOT failure.
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005