Trip odometer not working

My coworker's '93 silverado 1500 with a 5.7, auto, has a trip odometer which has stopped working. The regular odometer numbers still work like they should, only the trip odo stopped working. The trip odometer won't even reset when the button is pushed, so it reads 437 miles all the time. Any ideas? Does anyone know if the gage cluster out of the '93 models are electronic or do they run off a speed cable? Any help ideas and/ or advise is greatly appreciated!

Should be electronic ,motor is in the head, the head will have to come out for repairs.

Thanks, maxwedge!