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CRT TV repair help - Turns off after few seconds + White horizontal lines

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madhushankarox

New Member
I'm trying to repair a LG CRT TV witch turns off (standby mode) withing few seconds after starting. Wired thing is this happens only if I have inputted video signals trough A/V inputs or if I have plugged in my antenna cable. Menu is visible and working fine without going to standby mode. Default blue screen also working fine.

Additionally pictures are very dark and cannot see anything until I august the G2 control (Menu and the default blue screen is visible without adjusting G2). But this cause horizontal lines and a big vertical faded line to be appear like following image.

IMAG0470.jpg

Please help me to find the issue for this. Thanks!
 

BeerBelly

Member
I would look first at some of the power supply capacitors in the horizontal section. These caps take a beating and will cause those symptoms.
Mat Electronics(here in the US) sells failure kits which include a handful of common failure parts. They may have one for your TV model.
 

madhushankarox

New Member
I would look first at some of the power supply capacitors in the horizontal section. These caps take a beating and will cause those symptoms.
Mat Electronics(here in the US) sells failure kits which include a handful of common failure parts. They may have one for your TV model.
Thanks for the reply.. I'm currently replacing electrolytic capacitors.. Will Mylar or ceramic caps may cause too?
 

ronsimpson

Well-Known Member
Most Helpful Member
The lines in the back ground are typical when G2 is turned up.
The vertical and horizontal section seem to be working.
The video amplifiers look like they are working.

It goes in power down mode when you give it a signal (antenna or A/V input). It works with a menu. Are there other inputs that work?
Who do you get to "Default blue screen"?

It acts like it is not switching from one input to another. If it does not find a sync signal (video) it just powers down.
 

tvtech

Well-Known Member
Most Helpful Member
Check out your RGB smoothing Cap...normally rated @ 10 to 47mF @ around 200V.

May help..I don't believe it will solve your problem though. I can tell you one thing though...IT IS NOT PSU related.
 

madhushankarox

New Member
The lines in the back ground are typical when G2 is turned up.
The vertical and horizontal section seem to be working.
The video amplifiers look like they are working.

It goes in power down mode when you give it a signal (antenna or A/V input). It works with a menu. Are there other inputs that work?
Who do you get to "Default blue screen"?

It acts like it is not switching from one input to another. If it does not find a sync signal (video) it just powers down.
Thanks for the reply. If there is no input signal, it's going to a blue screen like most of modern TV's. This blue screen is not turning off the TV.
Basically just only menu and the blue or empty screen with dots is working fine without going to standby mode. That happens only after inputting a video signal (A/V or Antenna)
 

tvtech

Well-Known Member
Most Helpful Member
The lines in the back ground are typical when G2 is turned up.
The vertical and horizontal section seem to be working.
The video amplifiers look like they are working.

It goes in power down mode when you give it a signal (antenna or A/V input). It works with a menu. Are there other inputs that work?
Who do you get to "Default blue screen"?

It acts like it is not switching from one input to another. If it does not find a sync signal (video) it just powers down.
That makes sense Ron. Unfortunately, I do not know that specific chassis. Maybe if madhushankarox could provide a diagram I would be able to help more accurately.

Regards,
tvtech
 

BeerBelly

Member
Shutdown in CRT televisions is generally caused by a high voltage problem or ripple in the high voltage. It can also be caused by excessive beam current on the CRT. Could the shutdown be a symptom of the G2 turned up too high?
 

tvtech

Well-Known Member
Most Helpful Member
Hi BeerBelly

The OP needs to source a diagram...from somewhere...otherwise we will just be guessing here. And that's no good/help.

Some sets I see here do indeed shut down if a fault is sensed by the Micro or Jungle or combination thereof. Line stage is normally shut down...set goes into standby.

Regards,
tvtech
 
Last edited:

HiTech

Well-Known Member
... and he needs to concentrate his troubleshooting in the blanking circuit/G2 level
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I saw the issue you are seeing only once. It was a short in the CRT. That's easy to track down with the pin out of the CRT.
 
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