Hi all,
Recently I've experienced two separate incidents in the lab where the X2 suppression capacitor (which is strapped across the mains input) has failed in catastrophic fashion.
The first incident happened about 3 weeks ago on a very old dual rail PSU (it was some obscure manufacturer and I forget the name). The mains capacitor suddenly caught fire (flames could be seen bursting through the enclosure) and the entire lab was filled with smoke - it was horrendous!!! We threw the PSU away.
The second incident happened today, again on an old PSU, but this time it was a HP 6634A. Again, the mains input cap went kablooey and filled the lab with smoke. This is a decent PSU so I'm going to replace the cap and put it back into service.
Anyway, I wanted to run this by the other forum members to see what experience other people have had with these capacitors. Has anyone else experienced it as a common failure mode? The component in question is quite high risk because it's literally strapped across the mains input and, if it goes kablooey, it's a significant fire hazard.
In both my incidents the supplies were very old, so perhaps age of the caps has something to do with it. Any comments about that?
I'm also tempted to try and test the quality of the mains input just in case we're getting frequent high voltage spikes which could explain the failure of these components. I am wondering if I can set up some sort of long term data logging system to take the measurements over a few weeks. I have all the kit I need around me to do some data logging. Does any one have advice about capturing evidence of mains spikes?