LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

[mojo7676]

Newbie to the forum and fairly inexperienced when it comes to TVs – I don't have a digital multimeter. Apologies if this post seems long, but I hope the details are useful. For at least the last couple of years, our LG 50pc55 has had a rather odd and annoying fault which we couldn't be bothered repairing. When you switched the TV on, after it had been off over night for example, it would take maybe 10-15 attempts to switch on either through the power button on the tv or the button on the remote control. Eventually it would come and all would be well. If you switched it off then switched it back on, it would come on again immediately. If you switched it off and left it for an hour, then it would take maybe 3-5 attempts to come on. Sound and picture were always fine when it was on. However, a couple of days ago, this stopped. All we have now is sound but no images. I've done a few trawls and I think it might be the Y-Sus board (read Tom66s helpful guide) but I can't be sure given the earlier problem with the multiple attempts to switch on problem. I removed the back to identify the part number (EBR36223601/EAX34151501) and can get a replacement board for around 30 quid but it might be something else, like the Y-buffer/s or power board, that needs replacing. Any ideas/comments highly appreciated. Thanks in advance.

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Doesn't sound like Ysus fault to me, normally if you had a Ysus fail the issue would be fixed not intermittent. Do you have a hair driyer this can help you diagnose things ?

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Yes I can get hold of a hairdryer.

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok, power the tv on from cold. Then start heating the Mainboard with a hair dryer see if the tv starts faster. If it doesn't start heating the Psu then the control board. I have seen the Mainboards on Lg plasmas cause this symptom here is a link to my video of a similar one that I had:

https://m.youtube.com/watch?v=66SeSEFVc-8

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok will do. Mainboard is the middle one, right? PSU and control board along bottom? Thanks

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

The Mainboard has all your Hdmi input and other I/O ports.
The control board is normally in the middle of the tv and has lots of white ribbon cables coming out of it going to the Ysus, Zsus and address buffers at the bottom of the screen.
The Psu has the mains Ac plug going to it and is normally is in the centre at the top of the tv.

Here is an example:

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Great that's really helpful. Will try this evening n see what happens then report back. Thanks again

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

No worries keep us updated

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok will do. Just one point... It's not an intermittent fault as such. Even when there was sound n image, it wouldn't ever turn itself off or exhibit any other problems. To me it was as if it needed to warm up abd then itd be okay and stay switched on. A bit like some cars I've had that take a while to start but once they get going they're fine

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Thats an intermittent fault lol known as intermittent start up

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Fair enough... Will be on with it in next half hour or so. Tbc...

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok mate.

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

So ok... Heated main board for a minute or so and then got a few clicks. Then heated the power board and within 30 seconds... TV came on with video. Am assuming then that this means one of these two boards are knocked but how do I know which one? Maybe I'll do it again tomorrow and see what happens when I heat the power board first. Or something else?

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok good stuff thats progress Now turn it off let it cool and repeat the same test on the Psu first let us know what happens.

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Ok will do... But might be Tuesday before I can get to it next. Thanks again

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

No worries glad to help

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

After getting it to work a couple of days ago, I fitted the back panel and mounted the tv on the wall. Tried the tv yesterday. It had been switched off over night and, as expected, no luck. I didn't have the time to take it off yesterday... but instead i just switched on the hair drier and left it blowing at the back panel from the top of the tv. Within a couple of minutes, it started working. Left it off last night and when i get home tonight, i'll take it off the wall and try to warm the power board but will start at one end and try to warm in a grid like fashion in case that can help pinpoint any specific element/component which might be replaceable. Will try to update tonight if i can or tomorrow at latest. thanks again.

[ReeceyBurger123]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Probably a bad start up capacitor, do you know what a capacitor is ?

[freakaftr8]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Yes it does sound like a bad start up capacitor, also have you checked for any broken solder connections or bad solder connections on the power supply? When your heating the board it has a tendency to flex and make contact where it is not usually making contact cold

[mojo7676]

Re: LG 50PC55 Plasma–multiple attempts to turn on; but now no image... help

Not 100% about capacitors - usually cylindrical? - but I'll take some photos of the board tonight and await further input... Thanks again