RCA L37WD12 LCD TV works fine then powers off and wont turn on

[nmg555]

I have an RCA LCD tv that i picked up for free that works when first turned on and will work anywhere from 15 minutes to 3 hours and then shuts off by itself. When attempting to turn back on the relays make a clicking sound and the red light goes off but the screen never turns on and the tv makes no sound however the red light will blink in response to any button on the remote that is pressed and sometimes will click and go back to standby by itself. it can take anywhere from 5-50 tries to get the tv to turn back on. and typically when its back on it stays on for as long as i need it. All capacitors look as though they are in working order. Not sure if there is a common problem on these tvs that causes this issue or perhaps theres some cold solder joints.

Any ideas or input is greatly appreciated.

[retiredcaps]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

It might be an overheating problem? Something gets too hot and then the TV shuts down. Try either removing the back cover and blowing a fan on it to see if it stays on indefinitely or using a hair dryer on warm/hot and try warming up some of the components to see if it shuts down quicker.

Or if you have IR temp gun, you can see if there are any hot spots.

[nmg555]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

Thanks for your input,

Unfortunately I don't think it's an overheating issue. Now it won't turn on even when it's been off for hours. It takes about 3 tries now to initially turn it on. Then it usually lasts 15-30 minutes and a hole lot more tries before it comes back on and stays on. I also noted that the tv has not been responsive to some of the attempts to turn the tv on. Could this be related to the small 5w/v board in the top corner by the power supply? I forgot what it is called.

It might be an overheating problem? Something gets too hot and then the TV shuts down. Try either removing the back cover and blowing a fan on it to see if it stays on indefinitely or using a hair dryer on warm/hot and try warming up some of the components to see if it shuts down quicker.

Or if you have IR temp gun, you can see if there are any hot spots.

[tom66]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

It does sound like a capacitor problem, and caps can fail without visible bulging. Can you post some pictures of the general layout and boards themselves? Retiredcaps' signature has info on the ideal pictures.

[nmg555]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

1st picture shows the layout of everything in the chassis
2nd is the power board. (blue capacitors are ones which i already replaced)
3rd is the small board in the upper corner of the tv the 5 volt or watt cant remember what its called.
4th is the underside of that board which seems suspicious looking for some reason.

It does sound like a capacitor problem, and caps can fail without visible bulging. Can you post some pictures of the general layout and boards themselves? Retiredcaps' signature has info on the ideal pictures.

[retiredcaps]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

2nd is the power board. (blue capacitors are ones which i already replaced)

Those blue replacement caps don't inspire a lot of confidence if they were purchased from Radio Shack as they are likely to be general purpose caps. A SMPS requires low ESR caps to work properly.

[nmg555]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

The problem was happening before I replaced those caps. For some reason I thought I was onto something but turned out I was not. But once I find the real problem I guess I will have to swap those out again with the premium ones.

The underside of that small board has dried up gunk spots could that be a leaky cap?

I'm no electronics expert but I plan to take some college courses eventually once I finish my degree. So I'm very much a beginner. I figured a capacitor was a capacitor as long as it has the same uf and voltage.

Those blue replacement caps don't inspire a lot of confidence if they were purchased from Radio Shack as they are likely to be general purpose caps. A SMPS requires low ESR caps to work properly.

[Mr Bill]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

That dried up gunk could be solder flux. The 3 caps that you replaced, were they bulged? I'm betting there is another cap on that power supply that has failed but not bulged. With the 2 transformers side by side and the covers over the power supply leads me to think that board gets pretty warm.

[nmg555]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

Flux makes sense seeing as there's no caps on the other side by the gunk. I'm sure it gets hot but it can't be overheating since it has the issue even when cold. I feel as though the tiny capacitors would be very unlikely to fail unless there was a manufacturing issue. I'm wondering if its the large main capacitor which is in the middle with the black top.

That dried up gunk could be solder flux. The 3 caps that you replaced, were they bulged? I'm betting there is another cap on that power supply that has failed but not bulged. With the 2 transformers side by side and the covers over the power supply leads me to think that board gets pretty warm.

[t.j.]

Re: RCA L37WD12 LCD TV works fine then powers off and wont turn on

get power to psu only! then test the big cap with dmm, seeing only one should be around 200volts| unless it says 400 on side of it!!be carefull that a good load of juice!