Hello

I'm trying to repair a dead LG 32LS570S LCD screen. The backlight work
OK, all the power supply voltages are nominal and the unit turns on and
off via the remote or the keypad, but there is no image. The service
manual says "change the main board", but first I want to ask here if
this is a known fault.

Thank you

--
Saludos
Miguel Giménez

On Tuesday, February 2, 2016 at 6:11:03 AM UTC-5, Miguel Giménez wrote:
Hello

I'm trying to repair a dead LG 32LS570S LCD screen. The backlight work
OK, all the power supply voltages are nominal and the unit turns on and
off via the remote or the keypad, but there is no image. The service
manual says "change the main board", but first I want to ask here if
this is a known fault.

Thank you

--
Saludos
Miguel Giménez

There are four causes of your problem: bad main, bad LVDS cable, bad tcon, bad display (display and tcon are often combined in cheap TVs). You can either start buying parts and throwing them at the TV or you can scope for differential signals and check the dc buck converters at the main and tcon for proper voltages.

"Miguel Giménez" wrote in message ...

Hello

I'm trying to repair a dead LG 32LS570S LCD screen. The backlight work
OK, all the power supply voltages are nominal and the unit turns on and
off via the remote or the keypad, but there is no image. The service
manual says "change the main board", but first I want to ask here if
this is a known fault.

Thank you

--
Saludos
Miguel Giménez

You didn't say if you have sound and channel change etc.
Service manual's here if it helps.
http://elektrotanya.com/lg_32ls570s-.../download.html

Kenny Cargill

El 03/02/2016 a las 19:57, Kenny escribió:
You didn't say if you have sound and channel change etc.

No sound, but I don't know if the device is properly tuned (it's not
mine and comes from another repeater area).

The channels may change, but I can't see the change.

I already had the service manual you pointed (thank you), but an special
remote is needed for almost any test. I followed the debugging procedere
until I arrived to "change main board".

Thank you.

--
Saludos
Miguel Giménez

Hello Miguel,

It`s been some time!

Maybe you could look at the video output from a scart or AV socket if it has one to see if something runs inside. Or input some signal in a scart with a set top box that enables the autoswitching signal and see if sound comes out the speakers.

Greetings

Hello Miguel,

It`s been some time!

Maybe you could look at the video output from a scart or AV socket if it has one to see if something runs inside. Or input some signal in a scart with a set top box that enables the autoswitching signal and see if sound comes out the speakers.

Greetings

El 04/02/2016 a las 19:56, Jeroni Paul escribió:
Hello Miguel,

It`s been some time!

Maybe you could look at the video output from a scart or AV socket if
it has one to see if something runs inside. Or input some signal in a
scart with a set top box that enables the autoswitching signal and
see if sound comes out the speakers.

Greetings


A long time, certainly. It's a pity the decay of es.ciencia.electronica,
as it was one of the few places where you could meet people near you
interested in electronics. I suppose it's because now few people want to
do their own circuits, and those who do prefer using a kit or an
Arduino. I'm still subscribed to the group, but the activity is near zero.

I'll use a DVD player connected to the SCART, because in my lab I don't
have antenna and I can't use a DVB receiver (I only repair TVs from my
parents or close friends).

--
Saludos
Miguel Giménez

Miguel Giménez wrote:
El 04/02/2016 a las 19:56, Jeroni Paul escribió:
Hello Miguel,

It`s been some time!

Maybe you could look at the video output from a scart or AV socket if
it has one to see if something runs inside. Or input some signal in a
scart with a set top box that enables the autoswitching signal and
see if sound comes out the speakers.

Greetings


A long time, certainly. It's a pity the decay of es.ciencia.electronica,
as it was one of the few places where you could meet people near you
interested in electronics. I suppose it's because now few people want to
do their own circuits, and those who do prefer using a kit or an
Arduino. I'm still subscribed to the group, but the activity is near zero..

I'll use a DVD player connected to the SCART, because in my lab I don't
have antenna and I can't use a DVB receiver (I only repair TVs from my
parents or close friends).


Yes, it was nice to see discussions about common products around here. At that time some ISP dropped their news servers and a known free one converted to paid service. I think that wrote the definitive death to Usenet here in Spain.

Back to your TV, since the purpose is to check if the main board operates, a DVD playing a disk can be used connected in a scart socket. Most DVD players enable the switching signal (Scart pin 8 with 12V) that should make the TV set switch to that input automatically and you should hear the DVD sound through the TV speakers. If you don't, chances are the main board is not working and you should look at a problem in the power supply or main board.