(Submitted by Andrew Wright aka Bun-Bun)
After acquiring a used Cubex Duo 3D printer, I discovered the heated-bed did not actually heat. The PID controller for the unit appeared to be functional and the relay could be heard actuating, however upon testing with a DMM I found the relay to not be contacting. Opening the PID controller revealed a cheapo chinese relay which made me think if there was a better way: an SSR would be quieter (silent) and more reliable than a mechanical relay in the given application. With the help of Scott Walde I sourced an SSR and tested the PID output with a resistor and LED to prove an SSR would work. I drilled and tapped a hole to attach the SSR to the PID enclosure and applied thermal paste; the enclosure is the heatsink for the SSR. I bypassed what was the chinese relay and used the PID connections to wire up the now externally mounted SSR. It works perfectly and any concern on heat dissipation of the SSR is nullified in practice: the heat from the SSR is only enough to take the chill off the metal enclosure, not warm it up.