Wanhao Duplicator i3 Mini Heated bed modification

I bought a Wanhao Duplicator i3 Mini from ebay for about $40 broken, figuring that it would be an easy repair. The screen was apparently not working, so i figured that it was probably a faulty LCD panel. After replacing the panel I soon discovered that the problem was somewhere else, and with a bit of probing around with the multi-meter I soon found the culprit which was the 74HC4050D hex level shifter… which essentially just translates the logic state levels between 3.3 volt and 5 volts for the Arduino. This is used not only for driving the LCD screen but also communicating with the SD card, so if you have one of these printers and the SD card is not functioning, this is your culprit.

After getting the printer running I soon discovered how annoying it was to not have a heated bed with constant bed adhesion failures… so it was time to add a heater to the bed! After looking around online I soon found that a few people had used the “Bed Add” pins from the motherboard to add a thermoco