Click here to view the video Most combo organs will have at least one or two bad divider circuits, often several.Dirty key contacts are pretty common, too (see the cleaning procedure, below), and a bad oscillator pops up now and then.Continue to do that until you hit the 16' foot tab, which will be the lowest divider in the chain.
If it fails in all octaves, then the oscillator is bad.
If it plays correctly in the lower octaves, then you probably have a bad key contact in that top octave.
You'll want to work with only one voice at a time, and ONLY even-numbered footages, and ONLY Flute (or flutelike) voices - ignore any fractional voices or mixtures.
Fractional voices, mixtures, and non-flute voices may add additional notes to confuse the procedure.
If the octave is monophonic (only one note plays, no matter how many keys you press), then there's probably a single Bass Divider circuit that serves the whole octave.