1990 Honda Prelude speedometer

Check your fuses.

Look for the relay labeled IOD and/or Memory IOD in your power distribution center..

Is your speedometer cable making any loud noises?

The power distribution center will be located under the hood in a black box. It is usually located next to the battery. It will have many fuses and relays and the cap should have a label. If not, just check them all. If you didn't already do so, check the fuses in the fuse box (inside the vehicle) as well. If it is not a fuse than it may be a short in the circuit that is attached to your instrument panel. Below is a diagram of your vehicles instrument panel..

It should be labeled IOD for Input Output Device. It defers from vehicle to vehicle. It should be one of the fuses though (around 20 amps), not a black relay. Once you find it, unplug it for 5 - 10 minutes then re-insert it. This will reset it and should get the gauges working again, assuming the fuse is the problem.