by Charlie Piper Member of LA3D Club from his Technical Pages
WHAT IS THE CONDITION OF YOUR TDC PROJECTOR ?
The typical problems with the TDC projector, not necessarily in this order are: lamp condition, polarizer condition, dirt accumulation, optical alignment, changer operation.
LAMP CONDITION
Using a tissue or a rag so as not to 1 eave fingerprints, remove ·the 1 amps by turning counterclockwise and examine them. As a lamp deteriorates over life, tungsten evaporates from the filament and deposits on the glass bridge at the top and on the glass envelope. If there is much blackening of either, you may be in for a burnout. Look
at the filament with a magnifier. If the coils show any non-uniformity, burnout is
imminent. Always keep a pair of spare lamps, and replace both when required.
POLARIZERS
To remove the polarizers loosen two screws about one turn and lift the assembly straight up. Test each side for extinction by crossing it with a camera polarizer
or a pair of viewing glasses. If your polarizers do not extinguish properly, or are
spotty, get replacements from Reel 3-D Enterprises. For light dusting, use
a soft brush. For real dirt, remove the polarizer films and clean them in warm water
and dishwashing liquid. Don't handle them except when in the wash water. Remove most
of the water with a photo sponge and allow to dry in air. then dry, reassemble. You
can't put them in wrong because they are coded.
OPTICAL ALIGNMENT
The mirror behind each lamp should be adjusted so the image of the filament falls on
the filament, with the image coils between the real coils. You check this by leaking into the projector from the front. Illuminate the lamp filaments with a small flash1 ight. The filament image should fill the entire aperture of the lens. If it does
not, the condensers are probably not strong enough. The standard model has loose condensers and heat glass held the rods by means of a spring clip. The shape of
the groove on the rod tells you which way the elements go. Clean. these items with
water and dry with a paper towel. Remove and clean the end elements of the projector lenses likewise. Screw the left lens in tight and leave the right a few turns loose.
When setting up, first focus the left with the focus control, and then· focus the
right by unscrewing its lens. After that all focusing is with the focus control.
CHANGER PERFORMANCE
The item which causes the most consternation on the TDC is the changer on the standard model. This changer places the slide in a fixed groove at the bottom and moves
it under a grooved spring at the top which is supposed to locate the top in the same
plane as the bottom. If the spring is distorted or loose, the slide will not locate
properly in the top spring and the slide will be cocked and jam. Operate the changer in daylight out of the projector to make sure that no matter how the slide is placed jn the starting end of the bottom groove it straightens up when it reaches the spring. Make sure the spring is centered and has some but not too much tension. Sight along the outside of the changer and straighten anything which is out of line. v!hen in the
projector, the changer must be free of shake, and must be perpendicular to the optical axis. Check this by using a square or by projecting a test slide and noting that top and bottom are in focus at the same time. If necessary, shim the changer so that it
is perpendicular. Tilting the screen will not correct top to bottom focus error.
MISCELLANEOUS
It should not be necessary to do anything to the blower as long as it operates and
produces a good stream of air. The noise of the blower is something you have to live
with. The reason the TDC never burns up slides is that it is the only common projector to have an adequate cooling sys.tern. The quiet projectors overheat. There are
exact replacement quartz iodine lamps for most projectors. The advantage that they have is somewhat longer life and less light decrease with age, but they are not any brighter when compared with a new tungsten lamp. They cost quite a· bit more.