Repair guides for displays (or monitors) for computers or other devices with video output.

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Dead 31MU97-B monitor, power board OK.

I switched my 31" LG 31MU97-B off at the wall power socket and when I switched it on again a few hours later it was dead. So, untouched between switching off and switching on.

Dead means absolutely dead – no power light, no sound to indicate it has switched on, no message about powering off in a few seconds to save energy, no sign of a backlight.

I have taken it to a PC repair shop and to an electronics company that deals with monitors (but more usually the industrial type) and both say no blown fuses, no bulging capacitors and that the power board is OK. The latter thinks the display panel itself is probably OK.

Since there is no power light, which is presumably low voltage, I'm thinking this must mean something is causing the power board to trip or shut down (almost instantly). Is it (almost) inevitably the mainboard or has someone any other suggestions? Would I be right to think the power board is capable of shutting down when feeding into a short or too high a load or demand from the mainboard?

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If the power board is OK the power ON light should appear. If you disconnect the harness from power board to mainboard, are the voltages correct? There's a polyfuse in series with the mains input, it could have gone entirely.

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The monitor is currently with an electronics company – I've no practice pulling bezels apart, my multimeter hails from the late 1960's and it's decades since I wielded my soldering iron.

I imagine disconnecting the power board from the mainboard is what they did, though when I spoke to them they hadn't spotted the existence of the power light.

According to these people:

a dead monitor can result from a problem with the mainboard. Certainly I'm wondering what conditions must be met for the power light to come on.


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