Hi Jumper,

Thank you for your input.

I changed the resistor for a 470 ohm.

I am reading 4,92 v between rb0 and ground
and 4,92 v between TIL111 pin 1 and ground

I am reading 8,35v between TIL 5 and battery and the battery produces 8,35 v.

I tested my piezzo on two 9v batteries in series and the sound output is greatly reduced when I drive it with the TIL111 compared to driving it directly with the batteries. The voltage readings of the batteries and the TIL11 output are the same.

Solution?