Newbee 3rd gen speedo not working

[hiluxsurf 3.0 intercooled]

Hi everyone, new here and could do with some help please. Got a 3rd gen hilux surf intercooled model with the electric speedo clock which stopped working a while back, I removed the clock and saw the circuit board had burnt from the back, so got this repaired however it burnt again. So could someone please tell me what is causing this to burn?, is it the speedo sensor?

Any advice would be fantastic
Thanks alot
Dan