This is a common problem on these plasma TV's. The problem resides in the high voltage boards known as the X and Y Sustain boards.. You can purchase them here for a very reasonable price:
http://www.discount-merchant.com/Y-SUSTAIN-FOR-42-PLASMA-TV-PN-6871QYH036A-p/sku9510.htm

The above link is to a Y-SUS board. The X-Sus board is often the 2nd cause of failure and can be found here:
http://www.discount-merchant.com/X-SUSTAIN-6871QZH041B-6870QZE017D-6871QZH052D-p/sku9509.htm

To test which board is failing, you need to check voltage input to the YSUS board first... Input should be 120V from Power supply, output should be above 250V.. Do this test with XSUS disconnected. IF 250+V exists, then XSUS is damaged. If not, then the YSUS is the faulty part.

I know it's rather late to post this but just thought I'd post anyway, maybe you still need the help. If you get no sound and no picture but yet an amber light (yellow) also if you heard a pop sound from one of the fuses, there is a good chance that you YSUS board has take a turn for the worst. There are kits that you can purchase for $200+/- that will get you back up and going....for 5 more years.