XR2206 Function Generator Kit on LM2917N-14
The 555-based signal generator very probably has an output which goes down to almost 0 V.
With a 12 V supply, the output of the XR2206 function generator will be centred around 6 V.
Here is an oscilloscope display showing what you are working with:

The yellow &quot;1&quot; marker on the left is at 0 V. The vertical scale is 2 V/div. I set it to show all the measurements.
Looking at the datasheet for the LM2917N-14, it seems to me that you need a 10 kΩ, or maybe 15 kΩ, resistor instead of the 1N4148 diode, so that it makes a voltage divider to raise the switching threshold for the LM2917 to a sufficently high voltage.