Need info on where to cut oncidium spent flower spike?

[PaphMadMan]

As already noted, Oncidiums do not normally re-bloom from old spikes. You will need to wait until new growths are mature enough and the plant is happy enough to send up a new spike. Old spikes can just be cut back far enough to not be unsightly, or as far as you can manage without damaging sheaths or pseudobulbs, your preference.