I don't think there is a step by step guide to build a pretreater anywhere on the internet. If you are a serious builder and want to complete a build then the only option is to buy Andys kit from the store . This will give you the best head start as you will have support from the forum. DIY pretreaters are fairly new to the DTG world i only know of 2 and thats my machine and Andys. I could give you my code but i don't think it would do much as you would need to order the PCB and solder the board yourself also i cant give much support on the build. If you truly want to do a build go with Andy , Excellent support forum and pre made boards!