Hello Peter,
I should have mentioned that after a month of no response I went ahead and cut the trace and moved the jumper on one of my displays. The address didn’t change. That’s when I gave up and used the i2c mux.
I’ve suspected that I may have defective units so it will be interesting to see if moving the jumper changes the address for you.
The other issue that has not been answered is why does the schematic, the wiki, and the silk screened legend on the pc board indicate the default address is 78 but it is actually 3c? Since the board you have also is addressable at 3c I suspect you’ll get the same results I did, the address won’t change. I’m hoping I’m wrong. Please let us know how it goes.
One other note, 0x3c is half of 0x78 so that leads me to believe there is a higher order address bit not correctly set. There is probably a simple defect in the layout of the board causing the issue.
Thanks!
DarkStar