LCD HDTV Troubleshooting Help

LCD TV's don't use high voltages, the only high voltage is from 100v/230v input, the only high voltage could be from the back-lighting (those foils that need high frequency, high voltage, but low power, forgot the name), but these days the back-light is mostly led's

This has a cold cathode florecent tube back light.

A good starting point is the power supply. An old timer technician will not believe the crappy design quality of today's switching power supplies, designed to work reliably only in class 10 cleanrooms, else programmed to start failing not long after warranty expires. The -should not be there in the first place- high heat, usually damages the electrolytics first, and because of that, other components may fail from unfiltered spikes, before supply eventually fails to power-up. S.M.

I've checked over the power supply components, and don't see any obvious problems. I am trying to determine the expected voltages before checking with a meter. The cable to the inverter board has silicon tubing on each wire which makes me think that this is a relatively high voltage.

I don't buy "accidental" failures that happen ALWAYS. Some may not agree with me, but deliberately putting a self destruction time bomb on a consumer product, so you can sell me your next product sooner, is not my idea of fair trade. Whatever. S.M.

You may be right .. the FLOOD of HIGH failure rate caps has been going on FAR TOO LONG to be coincidental !!
The SAME failure mode seems to " suddenly happen " right after the manufacturers obligation to SUPPORT the product expires . AND ... it seems to happen more and more frequently with WIDER assortment of consumer goods from China !
MAYBE ... at FIRST ... it was a manufacturing defect in the strictest meaning of the term ... but I am beginning to suspect that this is now " engineered in " to the product life cycle formula.

Those " defective caps " are like a countdown timer to product failure, and I believe they are USING that to their advantage !

Hi !

The bad news is that 13 blinks is the code for a bad LCD panel .

The GOOD news is that BEFORE I knew this , I managed to fix 2 of these by replacing all the electrolytic capacitors on the power supply board . The capacitors were NOT all bulged up on the top , but testing them with an ESR meter revealed a LOT of very high ESR ( bad ) caps. After finding about 5 or 6 , I just gave up testing and decided to replace them all.

My guess is that the failing caps were either causing a lot of noise in the DC voltages, or were causing some of the voltages to be lower or non-existent .
In BOTH cases the people commented on how much sharper the picture looked when they got the sets back, so I'm thinking it was the noise issue .

Hope that helps

It has been the experience of a friend who regularly fixes these TV that the electrolytic capacitors are a major cause of problems in the PS boards. The high frequency ripple and the miniature size seems to be their downfall. Replacing them is certainly a good place to start. Try to buy switcher rated ones and use higher voltage with larger can if possible. This will help with the lifespan.

When my LAST Dell computer failed, it was due to fubar electrolytic capacitors. All of them were surface mounted and in such circuit density that it was impossible to replace them. I would have had to replace the entire motherboard, and nothing other than the original motherboard would fit in the chassis.

To quote E.A. Poe's raven "Nevermore!".

Bill

Did you ever measure the output voltage or put a scope on it to actually determine the problem.

I have put the set aside for now, but may get back to it. The question that I was trying to find an answer for was "what range of voltage and signal charistic should one expect for the from the power supply?, DC? AC? Frequency if AC? pulsed?

Thanks

http://www.docs.sony.com/release/KDL40WL140.pdf

http://esupport.sony.com/US/p/model-home.pl?mdl=KDL40WL140&LOC=3#/manualsTab

http://www.ehow.com/how_6011902_completely-sony-tv-blinking-led.html

http://www.youtube.com/watch?v=BLkyFXv2-i4

http://www.youtube.com/watch?v=YGTOWl0nOkQ

Check out shopjimmy.com. I replaced both inside component boards for a panasonic LCD television for about $100.00.

The VOLTAGE on the backlighting outputs is not very CLEAN , and the voltage spikes on it can exceed 1500 volts . Not a very good idea to attach a regular multi-meter to to those terminals.

Some basic LCD trouble shooting tips ( old timer style !!! ) can be learned by watching this guys series of vids on youtube.

===> http://www.youtube.com/user/GrantsPassTVRepairs?feature=watch

As an old vacuum tube guy you'll appreciate some of the test methods he uses .

Hope that helps