MODEL: PS42C7HD
FAULT: The plasma display shows no picture or the picture has significant maldischarge. Maldischarge includes unlit patches of display, overly bright parts, sparkling/unstable pixels or unlit pixels on colour bands.
DIAGNOSIS: Requires an oscilloscope. Should check Y-main waveform (was only about 20Vp-p when I checked it, should be >400Vp-p)
FIX: Replace 100uF 50V cap near yellow trafo on Y-main board
--Also encountered this fault with same model--
MODEL: PS42C7HD
FAULT: Clicking relay, no picture or sound
DIAGNOSIS: Identify shorted sustain board (X-main or Y-main.) Unplug either board in succession and see if set stops clicking
FIX: Repair or replace the X or Y-main board.
--And this one, too!--
MODEL: PS42C7HD
FAULT: Maldischarge but the 100uF cap is OK.
DIAGNOSIS: N/A
FIX: Adjust Yrr/Yfr controls. Drop Vs by about 5V.