[Mondial]

Seems like the oscillator freq is not tracking the resonant freq of the antenna and RF coils over the full broadcast band. I wonder if someone replaced those coils with ones from a later model with 260 kc IF?

What I would try is to compare the osc freq with the dial calibration of the 90 across the broadcast band. Start at 550 on the dial and receive the osc signal on your digital comm receiver. Osc should always be 175 kc higher than dial indication. Proceed up the band and record dial and actual osc freqs every 50 kc. If the osc freq differs from dial reading by anything other than 175 kc across the band then there is a tracking problem.