[Mondial]

How accurately are you setting the function generator to exactly 470 kHz to align the IF? Do you have a frequency counter to accurately check the frequency? If the generator is slightly low in freq, the trimmer may not have enough adjustment range.

Without a frequency counter you can confirm frequency accuracy by listening for the second harmonic of your generator ( 940 kHz ) or third harmonic ( 1410 kHz) on an accurate digital AM radio. Setting the function generator to triangle will produce higher harmonic content for a stronger received signal.