This is all there is on the internet:
http://www.cnc-in.cn/pdf/4%20Axis%20...er%20board.pdf
There are no schematics available and no documentation or instructions came with the board. Mine has a heat sink and 12v fan covering the
TA8345H chips. I haven't had any smoke or bang and all LED'd light up.No dark spots or evidence of a burnt circuit board on either side of the board. I am using the wiring color scheme for A+,A-,B+,B- given by the stepper mfg, and I am using the Mach 2 controls in the linked document.
Doug