Like so many others - my LG Plasma 42PC3D - can hear the sound but now picture. Where do I start to figure out what is wrong with it?

Sounds like you hit favorites button.

Check its speaker/s or its headphone socket (if any). Check its audio output card too. Contact any service technician or the authorized service center for LG. Gopakumar Gopalan Google

Subject says no sound but picture, but problem is mentioned is have sound and no picture. Which is correct? Anyhow try the following: Try changing the input device to something you are sure, works such as a DVD player. Look for any loose contacts in RC jacks/sockets/Cable.

it is going to be a failure of the Z sustain board if you can see dark video. you can either replace the Z sustain board or the IPM that is bad on the Z sustain. the board is about $175.00 or so part number is 6871QZH034 I THINK.

how dar is the picture ?
i can help you if you have more details

I was helped by your online tech....Wiz

Thanks,
Mike

One of the SUS panels will be defect.On these panels you will find several fuses,the panel with the broken fuse must be replaced.
Sus panels are the panels with the big cooling blocks.

Unfortunately, you'll have to replace the whole plasma screen to fix it. It's the most expensive part of the TV.
The web link below is the cheapest place to get a new screen.
http://www.shopjimmy.com/catalogsearch/result/index/?q=lg+screen&p=2

If your TV is model 42PC3D, they don't have your screen in stock right now. If you look at the other screens that are 42", the are $350 and up. Other web site will charge more than double for the same screen.

Sorry to give you bad news.

Wow, that sucks. I hope you catch those guys.
Your part number for the plasma display panel is 6348Q-E128N.
Partstore.com is the only place that I can find a replacement plasma panel. The cheapest they have is $1,045.95. :(
Shopjimmy.com sell replacement panels too, but they don't have one in stock for our TV right now. Their priced about $300
The only thing I can suggest is to find someone locally that is selling the model TV, but non-working with the plasma panel not damaged. Then use the panel off that TV.

Sorry I couldn't help you out more.
Please rate me based off the info I provided.

Have sound but no imagen