Grumpy_Mike:
I used MM74HC04M as buffers but that didn't work at all
Then you did not wire them right,
I used something like that:
But I didn't buffer SIN/SOUT only BLANK, DCPRG, GSCLK, SCLK, VPRG, XLAT.
I put that buffer between ATMega and first TLC5940, didn't work at all.