LG 50PC5D YSUS/ZSUS Issues

[YamahaFreak]

I have acquired this TV from a neighbor, whom said it did the 'pop of death', and now it works without a picture. I looked up info online and apparently the Y-Sustain and/or Z-Sustain boards like to fail in a manner that necessitates replacement of the whole board. I tried feeling the heat sinks to see if they're getting warm, and it appears that perhaps one of the two on the YSUS board isn't as hot as the others. What I'd like to know is if there's a more accurate way to know which of the two boards (hopefully not both!) are failed. The TV has run for several hours now without issues, other than no picture, obviously.