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I!.<br />
Develop High -Intensity Arc Slide Projector<br />
mechanics to do repair work. Many c<br />
these projectionists work only nights t<br />
the theatre and work at some other jo<br />
during the day. Therefore I present serv<br />
icing articles that are of practical hel<br />
every day, and I try to make them eas<br />
to understand and not too highly tech<br />
nical<br />
I suggest that you secure a binder am<br />
place these service articles in it fc fi'tP<br />
handy, future reference. I have ha^ (*'<br />
over 24 years of experience in servic lilof.<br />
work and in compiling technical data o<br />
projection, electricity and sound. Ya<br />
can be assured, through my experienc<br />
and my advisory staff of well-known et<br />
pha<br />
0inf<br />
gineers, you are receiving authenti SffW<br />
maintenance advice that will help yo<br />
keep your equipment in good operatin<br />
condition, whether you have service c<br />
not.<br />
I<br />
The<br />
Prop<br />
situal<br />
Mai<br />
rem<br />
Kenen<br />
COMMENT ON DATE SNIPES<br />
Bed.<br />
The new projector, adaptable for indoor theatres or drive-ins.<br />
Projecting pictures of a size and brilliancy<br />
comparable to large-screen theatre<br />
projection, a universal high-intensity arc<br />
slide projector which accommodates 2x2-<br />
inch, 3'/4x4-inch and 4x5-inch slides has<br />
just been developed by Strong Electric<br />
Corp. of Toledo.<br />
This new projector fills a long-standing<br />
demand for an arc slide projector capable<br />
of projection pictures to the mammoth size<br />
screens of drive-in theatres. It is also ideal<br />
for school, college and church auditoriums<br />
and classrooms, particularly where there is<br />
difficulty in darkening the room.<br />
In projecting 4x5-inch slides it will<br />
largely be employed by TV and motion picture<br />
studios for projecting background<br />
scenes before which the play is enacted. A<br />
50 C.F.M. capacity blower cools the slides<br />
so effectively that even dense slides may be<br />
projected for an hour or more without<br />
damage, it is claimed.<br />
CINE<br />
CLINIC<br />
Continued from page 33<br />
Good, straight reels should always be<br />
used for the takeup reel.<br />
How can I check loudspeaker (not a PM<br />
speaker) field coil for "shorts and<br />
grounds"?<br />
Loudspeaker fields which are suspected<br />
of being "open or shorted" may<br />
be checked with an ohmmeter. Testing<br />
for a shorted field you place the ohmmeter<br />
prods directly across the field coil,<br />
with your equipment data at hand it will<br />
give you the ohms. When a field is found<br />
open or shorted, sometimes you can repair<br />
It by taking off the insulating paper,<br />
and you find the trouble is right on the<br />
surface of the coil and can be repaired.<br />
The field winding is of very fine wire and<br />
34<br />
As compared to the yellow light of the<br />
Mazda, heretofore relied upon for slide projection,<br />
this high-intensity arc projects a<br />
snow-white light that gives the picture real<br />
brilliancy and sparkle. The projector is<br />
extremely simple to operate. It can be<br />
plugged into any 110-volt A.C. convenience<br />
outlet.<br />
Economical of carbons, the motor-driven<br />
arc burns 6mmx7-inch copper-coated carbons<br />
at 45 amperes and 21 volts to project<br />
7,500 lumens of light. The burning time for<br />
one carbon trim is 80 minutes. The optical<br />
system includes three lenses and a SVi-inch<br />
focus polished glass reflector of 24-inch<br />
working distance and lOli-inch diameter.<br />
The length of the projector is 78 inches<br />
and adjustable legs permit establishment<br />
of the optical center at a height of from<br />
36 to 55 inches. A projection angle of as<br />
much as 27 degrees downward and of 10<br />
degrees upward is afforded.<br />
care should be used in its repair. If the<br />
field is "open" your meter will not show<br />
a reading when leads are connected<br />
across terminals, of course. A test from<br />
either of the field leads to its frame will<br />
enable you to show up a ground. In<br />
making the latter test you should have<br />
wiring diagram handy as some fields are<br />
naturally grounded.<br />
/ find your articles on sound and projection<br />
very interesting and helpful. Keep the<br />
good work up! The advice you sent me on<br />
repairing intermittent movements and<br />
grinding compound worked fine for me<br />
and I was able to do a good job— thanks to<br />
you!— Odell Hunter, Pine Bluff, Ark.<br />
Projection and sound equipment is<br />
sold to thousands of exhibitors located in<br />
small towns where they cannot always<br />
employ experienced, competent projectionists<br />
who have sufficient knowledge of<br />
Now for a few whacks at the suggestio<br />
that we stick a five-frame black spot t<br />
our date snipes to conserve film. Thi<br />
may be commended as a patriotic effort t<br />
speed defense, but I think it is barking u<br />
the wrong tree. I have been conservin<br />
little date snipes for years, but not by sub<br />
jecting the audience to that annoyin<br />
black spot in there. Here is my way of fig<br />
uring: I just cut off one sprocket hole t<br />
make a splice. (When splicing duplitize<br />
color film, such as Cinecolor or Magna<br />
color, scrape the emulsion off the colo<br />
stock if making a splice that will show o:<br />
the screen, and scrape the back side of th<br />
black and white date strip, even if ya<br />
have to turn your splicer around. This wi<br />
avoid the red or blue strip that will sho^<br />
on the screen if you scrape the emulsio:<br />
off the black and white film.) Now by<br />
painful bit of arithmetic I arrive at thl<br />
following figures : Three splices a week wl<br />
remove six sprocket holes a week. Durin<br />
that week I will run it about 16 or moD<br />
times. In 20 weeks I'll cut off 60 sprocke<br />
holes and run the film 320 times. Sixt<br />
holes is 15 frames, not quite a foot, so m<br />
snipe is long enough for another 20 week*<br />
But, if you burn anything but punk t<br />
your lamp you have done considerabl<br />
cooking of that film, and maybe it is get<br />
ting sort of brittle and liable to tear. W'<br />
wouldn't want to risk that, would we? An(<br />
remember, we haven't subjected our patrons<br />
(the folks who pay our salary) U.<br />
the considerable visual shock of five frame.-!<br />
of black either. Let's conserve film anc<br />
stuff, boys, but may I do it my way? WhUi<br />
I'm fussing may I say this? Some conserving<br />
could really be done by crackinj<br />
down on those fellers who insist in winding<br />
trailers right on their rewind shaft<br />
It tears a foot or two all to.<br />
In five second.-;<br />
then, one nut tears up more film than oni<br />
of us can conserve in 20 weeks. If you an<br />
one of us who are blessed with a peacl<br />
of a manager, why not talk him into get<br />
ting you a stripping flange to wind th<br />
trailers on? They are like a one-sided ree<br />
and handy as a hip pocket. I have a six<br />
inch one and only once or twice have<br />
wished for a larger one.<br />
The MODERN THEATRE SECTIOU<br />
to oil<br />
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flte,<br />
j,To<br />
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