POLAR CAMERA
CHANGING THE BATTERIES IN THE CALIBRATION SOURCE

1) Make sure you have six (6) fully-charged Dynacharge C cells ready to
   install in the calibration source.  The battery charger is to the left
   of the computer.

2) Remove the four (4) screws holding the back of the calibration source 
   enclosure, and put them somewhere safe (e.g., the black plastic lens cap 
   to the right of the computer).  Then remove the back with its insulation.

3) Now remove the nine (9) screws holding the top of the enclosure.  There
   are four (4) on each side, and one (1) through the top surface of the 
   front (the piece painted black).  Slide the top of the enclosure backwards 
   until it is free of the front.  Remove it and its insulation.

4) The source is now visible inside its enclosure.  GENTLY try to slide it
   upwards and backwards to free it from the enclosure.  If it doesn't come
   out easily, remove the four (4) screws from the front surface and take it
   off, too.  The source should then lift out easily.  Put the enclosure 
   out of the way.  

5) Carefully remove the two large stainless steel slotted screws from the 
   top surface of the source.  They will be at diagonally opposite corners 
   of the source.  Gently turn the source onto its side, and separate the 
   top and bottom of the source.  The top has no fragile components and can
   be folded up.  The bottom contains the bulb, screen, and electronics, as 
   well as the batteries, so handle it carefully.  Fold the front and back 
   surfaces of the source down into its base, taking care not to touch the
   glass screen at the front of the source.  Now turn the source back onto 
   its base.  

6) The batteries are in the black enclosure at the center of the base.  The 
   lid is held on with two (2) screws, one at each side.  To remove each 
   screw, you need to lift up the end of the source nearest it to gain 
   access.  Remove the lid.  Note the ARRANGEMENT (polarity) of the 
   batteries, on paper if necessary, before removing them!  Then remove them 
   and place them in the battery dischargers to drain off the remaining charge.

7) A fresh set of batteries is in the battery charger to the left of the 
   computer.  Insert them in the clips with the same polarity as the ones you
   removed.  Make a small note giving your name, the date you changed the
   batteries, and their starting voltage.  You can measure this with the 
   digital voltmeter using the probe holes in the back of the source.  It 
   should be at least 7.5 V, and closer to 7.8 V; if not, replace them in
   the charger and wait at least a couple of hours before repeating this 
   step.  Then reattach the lid, taking care not to strip the screw threads.

8) Unfold the top of the source, and turn it upside down so the sides stand
   up by themselves.  Fold out the front and back surface of the source from
   the base, invert it, and gently slide it down between the standing sides.
   Make sure the front surface, with the glass screen, is at the same end as
   the curved cutout in the front lip of the top of the source.  The standing
   sides should slide inside the lip on the base of the source, and the front
   and back surfaces should be flush against the lips of the top piece.

9) Once you have the two parts together properly, gently turn them over onto
   the base and replace the large stainless steel screws.  Use only light to
   moderate force - they should not be screwed down tightly.  At this point,
   briefly turn the source on and look for light through the switch hole.  If
   you see light, skip the next step and go to step 10.

9a) (If you don't see any light from the source, go back to step 5. If the 
   batteries are in the correct polarity and all connections between the 
   batteries and the lamp are sound, you may have to open the lamp housing 
   and verify the circuitry there.  If there is circuit continuity between
   the batteries and the bulb holder, replace the present bulb with its 
   replacement inside the housing, USING GREAT CARE!  Then switch the source 
   on and verify operation.  If the bulb doesn't light, give up, reassemble 
   everything, and contact Dave Harris at the first opportunity to inform 
   him that the Polar Camera calibration source has failed.  Then arrange to
   ship it to him on the next flight out.)

10) Replace the source gently into the enclosure, making sure the screen is 
   at the same end as the projecting brass pieces.  Gently ensure the source
   is centered between the two ends so there will be room for insulation at
   both ends.  If you removed the front (black) piece, replace it with its 
   insulation.  When replacing screws, put all of them a few turns into their
   holes, but do not tighten any until all are in place first.  Again, use 
   only moderate force when tightening screws.  One screw holding the top of
   the enclosure has already stripped; try not to strip any others.

11) Replace the top of the enclosure with its insulation.  The front end of 
   the top has been scribed with the word "FRONT".  Use care with the screws,
   as described in step 10.  Then replace the back and its insulation, with 
   the holes over the power switch and voltage probe ports.  Careful with the
   screws!

12) No screw threads stripped?  No screws missing, or left over?  Did it take
   less than 20 minutes?  Congratulations!