The telescope runs away

Do the following in this order very quickly, whilst watching the synchros:

1. IF THE TELESCOPE IS NEAR A LIMIT, PRESS EMERGENCY STOP.
2. Else press the T/S DOME STOP button on the Control Desk. If this does not stop the telescope, then
3. Select ENGINEERING MODE and if everything else fails,
4. PRESS EMERGENCY STOP.

If pressing the T/S DOME STOP worked, then none of the main control software tasks have stopped, and the control system seems to be in order. Thus, check the following possible causes:

• Did you slew to the right place? Check on the Information Display.
• Were you using the handset when the runaway occurred? If so, the the cause may be a stuck contact.
• Did the runaway occur in quick or slow-motion drive? If it happened in quick motion, a stuck Baldwin encoder is a likely candidate. Check this by running the ENCODERS test task several times whilst moving the telescope slowly in Engineering Mode with the Slow Motion clamps on. If one of the Baldwin encoders is not updating, then remove it from operation as decribed in the previous section.
• Are the encoders reading correctly? Do the tests given in the previous section. If none of the encoders appears to be working, and especially if they all show values very close to zero and do not increment when the telescope is moved, yet all of the control software is operational, the most likely faults are:
  1. Catastrophic CAMAC failure. In this case none of the Information Display readouts give sensible values. However, if for example the focus is reading correctly, but none of the HA and Dec encoders works, then it is quite likely that:
  2. No clock pulses are reaching the encoder modules. Call the Duty Technician.