janbivalent

We just purchased a 1990 LS400 and noticed that the speedometer and tachometer do not register. The lights on the control panel are all well lit (day and night). The gas and temperature gauges both work correctly; however, the speedometer and tachometer do not work. Are there any suggestions at to what the problem could be and estimated cost to fix? I called a couple Lexus dealerships and received probable causes from circuit board replacement to dash computer malfunction. Help! Thanks.