Buzzing noise and no display on Philips 42" LCD TV

[Lanzersys]

Hello folks

I was out and about today and managed to spot a decent looking Philips 42" LCD TV in a dumpster and decided to take her home to tinker with.

What it does is when you turn it on, after a few seconds the backlight turns on and a loud buzzing noise starts and then it shuts off. The tv stays on, but the screen goes dark and the buzzing stops.

To get even stranger, this TV sometimes power all the way on and you can see the picture and menu, but it's still buzzing loudly and it only turns and displays picture like 1 out of 10 power ups.

I pulled the cover off and the buzzing sounds appear to be coming from the backlight inverters, more so with the master inverter.

If anyone has some info about this or know what needs to be done, i'd appreciate it!
This would be one less thrown away tv if I can get it working normally.


Here are some photos of what i'm dealing with here:

 

[Unolocogringo]

Just from looking at the pictures you have 2 bad Capacitors on the power supply board(brown one).
The 4 large caps at the bottom. Large silver cans with printed black plastic shrink-wrap
The top one is bulging quite a bit and the bottom one is also starting to bulge.
They should be perfectly round and have flat tops. Both of them have bulging tops, and are going bad. Common problem with cheap tv power supplies.
You can use a paper towel cardboard tube to trace down where the noise is coming from, Just hold it to your ear and slowly move it around until you find where the noise is the loudest.

 

[Lanzersys]

Just from looking at the pictures you have 2 bad Capacitors on the power supply board(brown one).
The 4 large caps at the bottom. Large silver cans with printed black plastic shrink-wrap
The top one is bulging quite a bit and the bottom one is also starting to bulge.
They should be perfectly round and have flat tops. Both of them have bulging tops, and are going bad. Common problem with cheap tv power supplies.
You can use a paper towel cardboard tube to trace down where the noise is coming from, Just hold it to your ear and slowly move it around until you find where the noise is the loudest.

Thanks for the reply

Regarding those 4 caps, I agree they are slightly bubbled on top, but it sure doesn't seem to be enough to cause an issue I think. It almost looks as if that's what they are like new. I took a couple more pictures up close to really see the tops, and all 4 appear that way. What do you think about them? :

As for the buzzing, is that an issue? or just a vibrating transformer? I inspected it and the bulk of the noise seems to be coming from the Master inverter, the lower transformer to be exact

 

[Unolocogringo]

Any time a capacitor shows signs of deformations it is bad or going bad. It will not provide the correct or stable voltage, which could be causing the transformer to buzz.

 

[Lanzersys]

Any time a capacitor shows signs of deformations it is bad or going bad. It will not provide the correct or stable voltage, which could be causing the transformer to buzz.

Thanks for the info, i'll go ahead and order replacements for all 4 of those caps and swap them out. I'll report back with the results probably on Wednesday. (Fast Amazon Prime shipping)

 

[Unolocogringo]

BE CAREFUL. Capacitors can carry a high current charge and zap the crap out of you or kill you. With the power unplugged ,hold the on/off button for a few seconds.
Then to be sure short across the capacitor legs sticking through the back side of the PCB using a well insulated Electricians screw driver. Just to make sure there is no remaining charge. You can not be too safe when dealing with high voltage electricity.
When you remove the old caps mark the orientation of the +/- legs on the PCB if not already printed on. And make sure you install the new ones with the same orientation. They are usually marked on the plastic heat shrink and on the PCB but not always.

Sorry I can't be of more help, but there is just no way of hooking up a meter to a picture on the screen.
I blew up your pics in paint shop pro and after carefully looking you may have one more bad cap on the I/O board. Position 2849 ,just below the top center mounting screw. Next to the yellow wrapped coil transformer.