LG22ls4d lcd tv

Gary submitted this idea :

Electrolytic capacitor failure is the most common cause of all failures of electronic items. If no one has yet published common component failure for your specific equipment, then you are on your own, breaking new ground.

Best bet is to look at all electrolytic capacitors and especially those around the power supply (it sounds likely to be a PSU fault). Look for any slight doming of the visible alloy top, or alternatively look for signs of the bottom seal being pushed out where the leads are.

I would agree with you regarding equipment which is low power and where the PCB is not subject to heating and cooling cycles, or one that doesn't get particularly hot.

Otherwise I would put dry joints very close to the list.

If I was the OP and all the electrolytics look good, I would be further scrutinise the PCBs for oxidised solder joints.

Not so likely to be a capacitor if the fault is intermittent. And although faulty caps can bulge, they don't always do so. Look for dry soldered joints in the PS - most likely round the transformers/inductors and high power transistors, etc.

Ambient temperature can be a big factor, a PSU might typically start OK when the house is warm but not when it's cold. A short blast with a hair dryer will often convince it to start and once started it will keep itself warm.

This phenomenon goes under the name "It was all right before you switched it off".

Touching the can of each electrolytic with an isolated soldering may sometimes reveal the culprit.

An ESR meter is the most efficient way to quickly test all the caps in situ, it's about time that ESR functionality was built into cheap multimeters.

Electrolytic capacitors often don't show doming or any other obvious visible signs when they fail, or are starting to fail.

The problem with lead free solder joints is that they could look S***y even when good.

I would go for capacitors as the most likely cause of the failure in modern consumer TV/PVR equipment, especially in switched mode power supplies.

Not so sure if it's an intermittent fault. Caps usually die and that's it.

You can get it when they are borderline... I had once LCD monitor that the backlight flickered on power up. It slowly got worse with time, to the point that sometimes it would never "catch" and eventually just shut down. Next start it might manage it etc.

Right... best thing to do is check with an ESR meter, but they tend not to be particularly cheap (well, about the same as a multimeter, but it wouldn't surprise me if the OP doesn't want to pay that much if they don't do a lot of repair work)

Yes, me too. Heat and vibration could do a number on solder joints and interconnects in the CRT era, but that's less the case with modern stuff.

I have seen quite a lot of diode and switching transistor failures in SMPSUs, however - they normally fail in non-intermittent ways, but I do remember one PSU where one of the rectifiers on one of the DC rails would sometimes fail under heavy load (i.e. most often at system startup), which sounds like the sort of behaviour that the OP's seeing.

cheers

Jules

Total and utter bollocks.

MBQ