Hot Heatsinks

I acquired a faulty TFT monitor from the place where I work. The screen itself worked fine, but the backlight wouldn't stay on for more than a couple of seconds. I figured it would be a dodgy capacitor and got straight into the job, taking the back off and having a good look around.

Visually, it was fine; no leaking or bulging caps or anything. So I fired it up to see if I could spot any problems. No, still nothing. Maybe it's overheating? I know, I'll touch the heatsinks and see how warm they are!

Bad idea.

After I had recovered, I measured 160V to ground on one of the heatsinks. Ouch. So my tip here is don't assume, like I did, that heatsinks will always have zero voltage on them.

Having read other peoples' experiences with similar monitor faults, it seems that they're almost always caused by a bad cap. The best thing to do is replace all the caps regardless of what they look like. I ended up giving this to someone else, who also couldn't get it working. Oh well.