55 sharp tv. I orderded a Main board that should have been board number 3655-1102-0150(4c) but I received a board number 3643-0072-0150(4a)? Some sites say this can be a subsitite part? Others do not?

Required board is available HERE and HERE
Click above links for price info.

It would be possible if you can go into service menu and write all settings and implement with the new board by going back in and changing what you wrote down.

Check all source is same or not
Try factory reset.

That the board which it have a square aluminun box at the edge of the board with a rounded bolt sticking out for inputs like ANT. input and AV inputs for like wires components inputs like multi colors like YRW,YRWGP holes for AV inputs also have HDMI hubs inputs for the high Def Pic.There are 6 HDMI inputs hubs for the tv Sharp Aquos LC-52d64U.Tvs Tuner board signal boards are also have to been known names to called as the tvs Main Logic boards and the tvs Mother boards also.U are fixing ur tv u must have to take it parts already.U can also compare the pictures between the tv Tuner signal board u are taking aparts out of the tv and the tv Tuner signal board you are buying they'll look axactly alike.The sticker of the serial numbers of the boards a few numbers in the begining on the tv Tuner signal boards should be the same also.

There will be some adjustments to do, after the replacement of this board. If you wish to get some details; visit the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/
Can't make sure about it. Sometimes there might be no more adjustments. Contact any service technician, and make sure about this.

In my experience the 4(a) appears to work the same except the picture is upside down. Looks like if you mount it upside down there shouldn't be any problems.

No. Both are different. http://electronicshelponline.blogspot.com/