Some typical problems with Model Ones
Tuner- variable capacitor needs replacement. You can turn it rapidly and repeatedly to clean it somewhat, but this won’t fix it for long..
Early volume knobs got noisy but were cleanable because they were open, later volume knobs were sealed and cleaning isn’t possible but service life was much better.
Selector Switches can loosen up, get noisy or just fail.
By the way there’s two distinct versions of the Model One
Original Model One 2000-2004
From 2004 onward was the Model One (A) differences were stereo from the output jack and the Selector Switch added the Aux position. There were some subtle changes after that, like a different tuner chip and that required some value changes in associated components, but performance was not measurably different.