How do you fix the speedometer light on a 1997 Isuzu Rodeo?

There a few bulbs behind the instrument cluster. You have to take out about 7 screws around the black bezel to free the cluster. You may have to unplug a couple of wires to get room to access the bulbs. My question is, which fuse powers the cluster lights? All mine went out at the same time, and there is no power at the dimmer switch (lower left of dash, by the hood release). All the fuses are OK, but one fuse socket, a 10 amp on the upper left of the fuse panel, has no power. It is identified as "Diode" on the fuse map. Any ideas?