Start up failure

I have a Beckman LS 6500Serial # 7070876 with a WYSE WT 9650 XE terminal that has not been used for almost 3 years. I turned on the counter the printer head on the dot matrix printer moved and the WYSE logo screen appears, then the auto-login screen with the countdown, when the countdown finishes, the screen goes black with a single cursor. Having read previous posts describing what sounds to me like similar problems, I pulled the front panel and checked the LED indicators. The vertical board on the power supply has the +5V, +15V, -15V and +24 V LEDs on. The horizontal board has a set of 6 LEDs then a set of 8 LED. Of the set of 6 LEDs, the Run and DIACLS are on. Of the set of 8, only the second LED is on (0100 000). From my interpretation of the diagram on the front cover, 0100 000 is the FRONT END BOARD TEST. Any advice on how to proceed from here would be very much appreciated.