Thank you for this comprehensive information Guenther.

    I have always wondered why a 455kHz IF was chosen, why this frequency ?

    And I have also seen circuits using a different frequency.

    Important to know when you would like to align a radio.

    Also interesting to know that in a combination of FM and AM, the IF stages share the same IF transistor (this can also be seen in your last picture).

    Ive been repairing a lot of these circuits at my former job and aligning those stages.

    Sometimes the small capacitors inside the IF coils tended to drift.

    This was primarily in TVs and I used an oscilloscope to find the resonant peak.

    If these coils were out of tune, the TV station was out of tune and the auto search function didn’t perform well.

    Many greetings.