Connected the Wii to new Panasonic 42 in plasma. Had been working fine on Sony Vega 27 in. Now picture quality is terrible and there is no sound. Checked all TV and Wii settings and unable to fix it.

yes. you find the main board for you panasonic plasma tv from shopjimmy.com.. good luck!

to get the part you need to go to the company to check what the problem is then if you will have to change circuit board you can get it right from them.

Fiend your solution direct from nintendo. Here is your solution....
http://www.nintendo.com/wiiconsole/prob676ijt65/solution

aaaaa10

The Wii can display on a HDTV, but keep in mind the output is only 480p. It is not true high definition, and it will only display this using a component video cable. There shouldn't be a difference with LCD and plasma.

You will also need to go to the display settings to force the Wii to display in 480p.

Try a different input (safe to assume your Sony has multiple?) and see if it is that specific input. Also, try a different device like a DVD player or VCR and see if you get the same result.

Good luck.

check that all leads are pushed in

check the cabling. It sounds like the cable has a broken wire, or the end(s) are loose.

it may cause by resolution mismatching, read the manual to find correct resolution needed. I have a service manual, if you want I can send it.

go here, it will work.  follow closely and read entirely!  it worked for me on a gateway plasma!
http://www.avforums.com/forums/plasma-televisions/462873-black-line-fault-hyundai-hpt4240-fixed.html

enjoy!
stephen

Same problem, 42" lg plasma

If the sound isn't coming the speakers then its cabinet expansion. Specifically between the panel and the front cabinet.
I believe Panasonic has a fix for this.