TV/VCR/Stereo Troubleshooting/lg 42lw5700 wont turn on


QUESTION: Hi Cleggsan,
Have a lg 42lw5700 of 4 years. Went out while playing. Now slow flashing red led bottom right corner.
Relay clicks when pushing on button, butno screen.
I'm instrumentation tech :-) So i checked fuses, cords, etc.
The readings on connector p201(the 12 pins between pws and mainboard ) are. Fromtop.0,12,12,12,0,0,3.5,3.5,0,24,3.5 and on
p832 from top 0,0,1.5,0,1.5,3.2,3.3,0.139. Do these voltages make sense ?
Tia ,

ANSWER: Can't say for sure because I am away from the office so I am going by intuition.

My guess is those voltages you gave are not normal.

Perhaps a new power supply board is needed.

First google your model number and search for similar problems.

Then google for power supply board which should not be expensive .

Then if you need more suggestions send me a follow up question.

Hoping this will help.

---------- FOLLOW-UP ----------

QUESTION: Hi Cleggsan,
As a tech, I did my job :) Found out that the voltage are corrects and pws works good (if I use jumper, back leds lite) But I discover that a series of models from LG suffer main board premature failing, so the parts are rare, and LG controls the flow, so my MB is 160US$ plus 30US$, so over 250 CDN$ ! The thing is, they sale you the exact same board that failed after 2=3 years :/ SO looking for request to LG conforms to quebec law 38 or I'll pursuit them for an example.
Wanted to share the knowledge so this racket of expensive parts stops.
Thanks for the answer,
Best regards,

Thanks for the feedback.  You have done a good troubleshooting job.

You are right about the mainboard being costly. Even on eBay they are expensive.

But if you wanted to do the mainboard replacement see:

Its a different model but similar in design.

For the age of the tv and the cost of repair and the likelihood of further failures it might be a wise decision to replace the tv with a new one (since they are much lower in price than 4 years ago when this one was purchased).


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Consumer Electronics of all kinds. Audio, esoteric audio systems and components, video, tv. Digital equipment for consumer use. Ham radio and automotive electronics. Note: I give advice on tv repair based on general consumer electronics engineering experience but I am not engaged in actual repair of sets. MAKE SURE YOU GIVE THE MAKE AND MODEL NUMBER AND AGE OF THE SET. BE SURE TO CHECK YOUR EMAIL FOR THE RETURN ANSWER DURING THE NEXT 24 HOURS AS I TRY TO REPLY TO ALL QUESTIONS WITHIN THE SAME DAY IF NOT THE SAME HOUR.


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