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370 RICHARDSON'S BLUEBOOK OF PROJECTION
It is caused by burning an arc too short. The only remedy is to carry a longer arc.
Carbons Do Not Deteriorate
(42) Carbons, properly stored, will be just as good ten years after storage as when made, provided they have absorbed no moisture. If they have, after a thorough drying out, they will be as good as ever. Store them, if possible near the ceiling of the projection room, where they will dry out thoroughly.
(43) Proper Carbon Combinations:
The following carbon sizes and combinations are those officially approved for National carbons. For carbons of other manufacture this information can be secured directly from the distributor.
D.C. MIRROR OR REFLECTOR ARC LAMPS (Angular Trim Lamps)
AMP. POLARITY SIZE and KIND
6-10 Positive 9/mm x 8" Cored Projector
Negative 8/mm x 8" Cored Projector
11-15 Positive 10/mm x 8" Cored Projector
Negative 9/mm x 8" Cored Projector
16-20 Positive 12/mm x 8" Cored Projector
Negative 10/mm x 8" Cored Projector
D.C. MIRROR OR REFLECTOR ARC LAMPS (Horizontal Trim Lamps)
SIZE and KIND 9/mmx 8" Cored Projector 6.4/mm x 8" Solid Projector 10/mm x 8" Cored Projector 7/mm x 8" Solid or Cored Projector 12/mm x 8" Cored Projector 8/mm x 8" Solid or Cored Projector 13/mm x 8" Cored Projector 9/mm x 8" Cored Projector 14/mm x 8" Cored Projector 10/mm x 8" Cored Projector NOTE : SRA carbons were discontinued by their manufacturer in 1942. Old type low intensity carbons thereupon took the place of the SRA type.
HIGH-INTENSITY ARC— DIRECT CURRENT
AMP. VOLT. POSITIVE NEGATIVE
75-90 54-60 ll/mmx20" H.I. Proj. 11/32" (or H")x9" Orotip Cored 120-130 67-69 13.6/mmx22" H.I. Proj. H" (or 7/16") x 9" Orotip Cored 140-160 70-72 16/mm x 20" H.I. Proj. 7/16" x 9" Orotip Cored (extra
heavy coated)
AMP.
VOLT.
POLARITY
10-15
54-57
Positive Negative
16-20
54-57
Positive Negative
21-25
54-57
Positive Negative
26-30
54-57
Positive Negative
31-35
54-57
Positive Negative