They are located on the mother board just on top of the scan reversal switches.
standing behind the projector with it on the the ceiling they will be deep inside between two boards on the far right hand side.
They are used to adjust the static width of the tube image before any dynamic electronic adjustments are made, this keep thing the heat generated in circuits like the convergence board to a minimum.
Adjustment is only reguired when a tube is changed these do not go out during the life of a projector.
Beacuse they use a ferite core to inflence a magnetic coil adjustment can only be made with a plastic adjuster ( infact on some projectors you might even melt a metal screwdriver or damage the projector because of the extra magnetic field from a metal screwdriver) So plastic only please.
If they do need adjusting chances are it will only be one that reqires doing. The adjustment proceedure is pretty straight forwards but bare in mind any stored settings like geometry or convergence after this will be complety screwed.
Sellect a genlocked pattern, swicth off the convergence in the service menu then adjust the raster shift (ignore the central area for the moment) so that the red or blue (which ever you are adjusting) is set so that the out side edges of the grid are overlapped by the same amount. Notice which colour has the smallest picture and screw the core down on the largest to match (don't go mad as there are no end stops and motherboards are not funny to replace.
Go back and raster centre and hey presto it's done.
Plastic screwdriver - good
metal screwdriver - bad, (hot, fire, damge to tubes circuits etc.)
This really is one of those if you are not sure with what you are doing could kill your projector so be carefull.