K8400 Heatbed Problem

Ok, so quick sitrep.
I installed a heatbed, power expander and external powersupply.
I’ve printed over 24h with this setup, then when I wanted to start another print (heating extruder, bed and turning on the fan) the power expander started to produce smoke…

I’ve attached some pictures, I really don’t know what’s going wrong so that’s why I’m posting it here.

The back of the power expander.

The front of the power expander.

Obviously the expander had to take too much current (without cooling you can’t go over 10A). Or there’s been a short somewhere.
You need to give more details about your set up.
What kind of heated bed do you have? What is the voltage of your PSU? Could you post a picture of the connection on bed side. Is there some isolation between the bed and the alu plate?

External Power Supply: Power Supply 12V/18A 216W
Heatbed: PCB Heatbed MK2
Isolator: Heatbed Thermal Insulator 200 (cork)

Picture of the heatbed connection (bottom view)

Looks like power supply used was a bit overkill, raby is right

Was it a cage supply? Or?

Normally the 24v cage supply’s run around 6.3ah 150watt which is more than enough for a mk2/3 bed,

I’ve set my heatbed up as a standalone unit, means I have more control over bed without touching printer at all

Looks like it’s pretty cooked, could well work still however did this not come with screw connectors on? So no need to solder?