Some TTL gate have antiparallel diode, other not. Connect 1N4148 diode cathode to TTL input, anode to GND and add a serial 560 ohm resistor from 741 output. Anyway +3V not a correct TTL high level, for best results use schmitt-trigger input gate....
Hi Sebi,
The lowest voltage that TTL allows as a high level is +2.4V. Besides, Mh says that he gets +5V anyway.
I agree with you that a Schmitt-trigger should be used because the old 741 is so slow and noisy that a regular TTL gate might output many pulses for each output transition of the 741.