Sparking ramps board and hot bed loosing temp

As per this video [youtu.be]
It seems my i3 reprap ramps board has started to spark on the extruder capacitor. I've also noticed a degraded hot bed heat. It seems the ceramic shunt starts to cook and the hot bed looses all temp.

Does this just needs me to resolder the cap legs or is there another problem afoot?

I can't say with 100% certainty, but if you saw sparks at the cap, you probably either have a short circuit or you witnessed the death of that cap.

Over-voltage is one way a cap can fail...caps should always be specified using voltage ratings well above your operating voltage (ex: Vss = 12V caps should be rated for 25V min where 25V is a standard cap rating).

Alternatively, if a polar cap (has a + and - terminal) then if the cap is installed and soldered into place reversed from its correct orientation and powered up, it can also catastrophically fail in the manner posted.

The reprap irc group got me sorted.

Seems i had 1 maybe 2 bad solders and a loose positive lead, this allowed the connector block to melt/burn and overheat the large thermal fuse. oops. [twitter.com]

They suggested to just join the 4 positive wires which went through the thermal fuse directly to the positive wire of the heated bed with a mechanical crimp.

I'll still be on the lookout for the spark on the control leg, but my guess it was from having the thermal fuse taking the 10amps+ load which was being switch on via the mosfet

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