Please refer to individual instrument web pages for faults specific to the instrument rather than IRPOL2.

Wave-plate is not rotating or ORAC hangs on a Pol move

Probable causes:

• Motor controller in the computer room is not switched on. The “Move status” on the EPICS screen should show “Error”, and the lights on the motor controller box, which is in the same rack as the Hewlett Packard computer (the controller is just below the HP) will not be lit – fix by switching this on.
• The HP itself is not switched on (nothing on the front display). There is usually only a small up-arrow on one segment, so this may be a bit hard to diagnose. Turn on the HP and reload its software/memory – see next item.
• HP lost its memory (after a power-outtage?). The “HP Status” on the EPICS screen gives an error (it reads something like “no such command” or “Undefined word”). First, try to Datum IRPOL from the EPICS screen (click datum and wait – it’ll revert to Idle once its done). If this fails, click on the “Reset HP” button on the EPICS screen; then click on “Reload HP”. The reloading part takes a minute or so (again, wait until the HP state reverts back to idle). Once idle you can try datuming IRPOL and then moving the waveplate from the epics window: select a demand position, 22.5 degrees say, and click on active. The HP status should read “O: No Error” and the HP state should go back to idle if all is well… 
  If you’re still having problems you may need to reboot the primary mirror support computer, but maybe check with Maren or Nick first before you try this…

The following are unlikely, but could happen. Your best bet for a fix in case they do are to call TCC, EGS or Maren:

• Cable disconnected (could be between the serial port and the HP, or the HP and rest of IRPOL). 
• Switch trouble (never heard of this happening before, but that doesn’t mean that it can’t…) 

Wave-plate assembly rotates but the data aren’t changing:

• No waveplate
• Arm not extended into position (this is done from the dome by the TSS)