I have a 42PFL3507H/12 Philips TV which I bought in 2012. It hasn't been working fine for a couple of months now. It won't turn on normally when I press the power button either on the remote or on the screen. I have to plug it out of power and back in five to ten times before I can turn it on.

I have searched through the internet but none of the solutions worked. I have tried plugging it out of power and leaving like that for a while. I have updated the software to the latest version. I have even taken it to the certified Philips TV service, but the repairman said that it worked perfectly fine when he tried to turn it on, although he did not show me that it works fine so I'm a bit sceptical because it still doesn't work at home.

What else can I do?

  • Good question. Welcome to H. I. S. E.! To improve the question a little, it might be good to provide some identifying information like the model, year you bought it, etc. Thanks for contributing! – whiskeychief Aug 14 at 15:09
  • sounds like a problem with the power supply, it's most likely on the way out. Maybe capacitors going bad? that would explain why the initial surge at power-on trigger the saftey shut down when the detected voltage levels are wacky. After a few aborts, there's enough residual charge to get them to perform enough in spec that it's not interrupted. i would leave it on to avoid the problem, but be aware that it's a matter of time before it gets even worse. – dandavis Aug 14 at 16:09
  • There shouldn't be a problem with power because the red light that signals whether there is power is on. – Hinko Pih Pih Aug 14 at 16:27
  • Does it have an external power brick and low voltage input into the TV proper? Or is it mains power right into the TV? Is it connectd via antenna or cable? If you unplug the signal cables (cable TV, HDMI etc.) does it behave normally? – Harper - Reinstate Monica Aug 14 at 17:31
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    @dandavis You are quite right, it was a bit too quick of a call that the power supply is OK just because the red light is on. I'm going to try to investigate the parts longneck suggested in his answer, including the power supply. – Hinko Pih Pih Aug 14 at 19:02

It sounds to me like your outlet or receptacle is loose and needs replacing. If you have the plug in and twist to put some side pressure on the plug will it work? If so it’s time for a new outlet.

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    It doesn't work. I've tried plugging it in other outlets which I know are OK as well, and it still didn't work. – Hinko Pih Pih Aug 14 at 15:06

Inside an LCD TV, there are effectively just a few major components:

  1. LCD matrix
  2. Backlight
  3. Power supply
  4. Backlight driver (aka, high voltage power supply)
  5. Main board
  6. Video board
  7. T-Con board
  8. Speakers
  9. Buttons
  10. IR Receiver

Some of these items may be combined with others (control board and video board might be the same) or not used (backlight driver usually only needed for CCFL backlights).

Let's work through that list and assess the probability of each component causing the problem you have described.

  • Your LCD matrix is probably fine. A failure here probably wouldn't stop the TV from otherwise powering on. A failed backlight probably wouldn't either.

  • A bad power supply might work enough to turn on the red light you mentioned in a comment, but fail to respond to a power-on command. A failed power supply is a likely candidate.

  • Your TV does not have a high voltage power supply.

  • The main board is responsible for receiving your power-on command and controlling the power-on sequence. A failed main board is also a likely candidate.

  • Your TV does not have a separate video board.

  • A failed T-Con board is not likely to cause your problem. And I don't think your TV has one.

  • There is a small chance that a shorted speaker is triggering a short-circuit protection mechanism, causing the TV to immediately power off. I would consider this unlikely.

  • When the TV does work, you state you are able to turn it on using the on-board buttons and the remote, and when it doesn't work neither of them work. Therefore we can rule out the button board and the IR received.

There is a small chance that if you open up the TV and remove the power supply board, you might be able to identify a failed component and replace it. More likely you will have to replace the entire board.

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    It kind of sounds like a bad capacitor to me. When it is discharged by unplugging, it starts working again. This leads me to think the PSU or main board, like you said. If the OP can get a repair tech to spend some time diagnosing it, rather than plugging it it and "it works", it should be an easy and low cost fix. I've seen people replace capacitors in TVs fairly often. – computercarguy Aug 14 at 18:02
  • to clarify one of your points: the TV is back-lit by LEDs, not CCFL. – dandavis Aug 14 at 18:44
  • When I turn the TV off, it always works immediately. Is that a sign that the control board is working fine? – Hinko Pih Pih Aug 15 at 10:38
  • I think it's equally as likely to be the power supply or the main board, but my gut is saying power supply. – longneck Aug 15 at 13:40
  • Thank you a lot for your help! – Hinko Pih Pih Aug 16 at 6:57

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