Dude, 50cm cable between each of 4 tlc5940 meen that the last one tlc5940 was on 2m cable... first two tlc5940 - no problem, third - sometimes few leds doesn't work (doesn't light up at all, rest work as expected), last tlc5940 - usually works but flicker alot, sometimes only one or two leds working and when thats happen its bad because it's overheating.
I tried really alot to make it work as it should but everything failed... now i'm waiting for new tlc5940 to arrive and then i try again but till that I try to use WS2803 because it's cheaper and as for now it doesn't overheat.
MM74HC04M buffer probably works correctly because if i use normal voltmeter to check voltage level output is in high state if input is in high state and in low if input is in low state but it doesn't work when it's connected between arduino and tlc5940 (without oscilloscope I can't check what's wrong and i didn't buffer SIN/SOUT because as far as I understand from datasheet there i no need for that).
In case of WS2803 I don't have problem with data connection but with my low arduino programming skills...
If I use common anode RGB LED everything works as it should no flicker or anything like that, but that way I can only use 6 RGB LEDs per one chip. With common cathode RGB LED and multiplexed RGB lines I could get 18 LEDs per chip and thats why I'm trying to do that...
I know that there are few good people here who can help me with tlc5940, I read everything what I found about tlc5940 on this board but my last hope... MM74HC04M buffer (read about it on this board) didn't work (at least for now) so I give a try with WS2803.