7  Troubleshooting 

7.1  Common Error Cases 

7.1.1  Gemini Does Not Start 

If the power LED is off, the display stays blank, and the buzzer does not sound, 

check the power supply and the power cable to the Gemini. Also check the 

polarity. Applying a voltage with the wrong polarity will not harm the Gemini, 

but it will not work. If everything looks correct, turn off the power switch and 

remove the cover plate from the Gemini.  Slightly wiggle the power switch and 

try again.  If this works, there may be a problem with the switch.  Contact your 

dealer in this case.  

If the power supply is delivering 12 to 18 volts, the power LED is lit and the 

buzzer continuously beeps, then the CPU will not start up. Check that the 

EPROM is properly inserted (see Appendix 8.7).  Ensure that the notch on the end 

of the EPROM matches the side where the notch is printed on the board (at the 

left side) and that it is completely plugged into its socket. 

7.1.2  Motor(s) Slew Uncontrollably on Startup 

There is probably a poor connection between main panel and the motor.  Check 

that the cables are firmly plugged into the motors and the electronics box.  If this 

fails, try replacing or swapping the cables, one of which may be defective.  

7.1.3  Mount Tracks in the Wrong Direction 

The tracking direction depends on the mount type and the hemisphere (specified 

by your latitude setting).  Use the   Setup   menu item to check that you have set 

the correct mount type and the latitude sign (`+'  for northern, ` '  for the southern 

hemisphere).  Set them correctly and restart the mount. 

7.1.4  Stalls While Slewing or Tracking 

The mechanics of your mount must be working smoothly to allow Gemini to 

operate correctly.  Check that both axes of your mount move freely when the 

clutches are loose.  Re lubricate your mount if necessary. 

Before attaching the servomotors to the mount, make sure the worms can be 

turned easily using your fingers.  If there are spots where you cannot turn the 

worm by hand, then it may be too tight.  Refer to your mount' s instructions and 

adjust the worm against the worm gear until you can turn the worm by hand, but 

there is only a minimum of play.  The worm may have some tight spots that 

require a looser mesh with the gear; this can result in some spots having more 

play than others.  The RA worm gear can have somewhat more play than the 

Dec., but it should not be more than necessary. 

Make sure that the correct mount type is set. Gemini is designed to drive different 

mounts at different speeds because of their different worm gear ratios.  

Gemini Users Manual 

7  

1