Part 2. The Basics |
been working on projectors for many years. But these individuals are rare and becoming
rarer, so you may have to fall back on your own projector’s handbook or technical manual,
which hopefully appear in Part 4 and Part 5. If all else fails, the following general principles
apply. Good luck.Additional contributions to this chapter are very welcome.
Getting Started
1. Moving parts don’t move freely
Machines that have been lying idle for a
while tend to gum up, that is, the lubricants in
their gears and bearings lose
viscosity, become sticky and act like glue in the works
.Check all moving parts, shafts, rollers
and bearings for freedom of movement.
If necessary, remove the parts, clean and
re-lubricate them. Test them before moving
on to the next job.
2. Which arm does what?
On a
strange projector and working without a manual it might be difficult sorting out
which arm does what. Use the following procedure to solve the mystery.
Make
sure the projector is not set in reverse or rewind. Check all knobs, levers and
switches for labels that might help. Put an empty reel on each arm. Open the
gate.
Rotate the inching wheel. Note if the claw moves forwards ie out then
downwards.
If it doesn’t, rotate the inching wheel in the opposite direction.
Note this as ‘forwards’
for the future. Continue to rotate the inching wheel
forwards and note which reel turns.
This is the take up reel. At the same time,
note which way it rotates. This is the
direction film will load during a
screening.
1.
Inside out film
(far) edge of
the film when you load the reel on to projector’s feed spindle, should be
rewound on the rewind bench.
off the top to the right
(clockwise). Now load the take up reel anticlockwise (instead
of clockwise,
which is what you would normally do) and wind in an anticlockwise
direction. The
perforations will stay on the far edge of the film and when you finish
the film
will be the right way around. Check to see if the head of the film is out.
If
not, rewind as normal, and it will be ready to thread.
Take up reel not rotating on test
Possible
causes:
a. take up mechanism might just be ‘lazy’
for a few revolutions of the clutch.
b. take up arm mechanism is faulty.
Remedies:
a. If time is short, fervently hope the
take up is just being lazy. Start the projector motor,
without switching on lamp
or sound. Keep a hand on the take up reel and assist it
manually. It may take
off by itself after a few seconds, in which case stop, unthread,
roll back the
film by hand and rethread. After the screening, take the take up arm to
pieces
and fix the problem.If this doesn’t work, switch to the
backup projector and
defer further work until you have time to do it properly.
b. Check take up arm components: belt
(stretched, faulty, cracked or broken) may
need replacing; oil could be causing
belt and/or pulleys to slip: clean all components
thoroughly; clutch may be
slipping: inspect, clean and replace parts as necessary;
drive pulley may be
slipping: check the pulley on the drive shaft is not slipping.
During
the Screening
1.
Loss of Loops
a. a badly made splice or an old splice may have created irregular spaces between
perforations, causing the claw to disengage from perforations
b. torn or damaged perforations.
Remedies:
a. Replace splice
remove the bad section of film and splice. If the film is beyond repair and has to be
returned, leave it as it is, move on to a clean section of film and rethread. Report the
damage when you return the film.
is having trouble. Be ready to shut down and reset the loops.
loop can sometimes be done without shutting down, provided there is enough slack
in the top loop. Below the gate, flick the film down with a pencil and the loop may hold.
Try several times before shutting down.
rethread or even open the gate to reset the loops. Just open the shoe on the feed
sprocket and feed some film through, creating enough slack for the loops. If the film
doesn’t slide freely through the gate, disengage the claw by rotating the inching wheel
forward until it disengages then try again. Reset the loops, test by rotating the inching
wheel, and resume screening.
inspect the film for damage eg perforation tears or repairs that continue into the feed
reel and are likely to cause more trouble. Perforation damage is repaired with special
white tape that is obvious when you first inspect the film. During inspection, if you
see a lot of white tape along the edge, you know you could be in for a bad session.
Before you rethread you will have to decide whether to skip some footage or risk
further interruptions to the screening.
2. The film runs through the projector
satisfactorily, but the screen image judders
at regular intervals.
Possible cause:
The film is old and
warped, and the perforations may be slightly enlarged.
Remedy:
Some projectors are better than others
at running damaged film. Find a projector
that keeps the film under tight
control during its journey along the film path.
TIP #1:
Wiping the film channel and the pressure plate with Inox or DW40 or
something
similar can sometimes help. Don’t leave excess lubricant on the metal
surfaces, a thin coating is enough.
TIP #2: Place
a fingertip under the bottom loop and gently press upwards.
While this procedure
can stabilize the image, it can be extremely tedious
if it goes on for any
length of time.
3. Dull Picture
Possible causes:
a. Poor quality
screen;
b. Lamp is on the way out;
c. Damaged reflector;
d. Badly adjusted
lamp;
e. Peripheral light affecting screen;
f. Throw is too long;
g. Wrong
lamp;
h. Dirty lens.
Remedies:
a. Replace the screen with a better
quality product.
b. Replace the lamp.
c. If the lamp and reflector are
incorporated in one unit, replace the unit.
If the reflector is separate, try
cleaning and polishing it, using methylated spirits.
d. In or close to the lamphouse you
should find a knob that adjusts the lamp’s
alignment. Try moving the lamp in
very small increments until it is right.
e. Unnecessary light, and daylight
seeping through curtains and blinds can play
havoc with the quality of the
screen image. You may not be able to do much
about daylight creeping in, but you
can make sure all unnecessary lights are
turned off. Try switching the lamp to
its high power position.
f. If the throw is too long, you may be
able to improve the screen image by
switching the lamp to its high power
position.
g. Replace the lamp.
h. Clean with a lens tissue or lens
cloth. Otherwise use a soft cloth and a good
quality window cleaner. Do not use
a dry cloth or ordinary household tissue.
4. Glare on Screen
Cause:
The screen is reflecting too much
light. This is not a problem with commercial
screens, but it can happen if the
wrong paint is chosen for a wall used as a screen.
Good quality non-reflective
white ceiling paint gives satisfactory results.
Remedy:
Get some good quality
non-reflective flat white paint and give the screen area
at least two coats.
5. Screen Image has Fuzzy Edge
Possible causes:
a. Lamp aperture edges
are not sharp
b. Screen image is slightly too small
c. Poorly masked screen
area.
Remedies:
a. Clean all four aperture edges with a
cotton bud dipped in isopropyl alcohol.
If this doesn’t work, inspect the
aperture with a loupe or large magnifying glass.
Remove hard deposits with a
plastic or wooden scraper.
b. Increase the distance between
projector and screen and reframe as necessary
until the edges of the image are
sharp.
c. Make the mask the exact size needed.
NOTE: Old prints sometimes have edges
that move all over the place and are
impossible to get right.
6. Focus Not Sharp or Difficult to
Adjust
Possible causes:
a. Screen too far off
square to the lens;
b. Focus mechanism needs attention
c. Pressure plate too
loose in gate
d. Dirty lens;
e. Badly warped or curled film.
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Remedies:
a. Re-align the screen or the
projector, or both.
b. Repair the mechanism.
c. Adjust the pressure plate springs in
very small increments until you are satisfied.
d. Clean the lens with a lens tissue or
lens cloth.
e. Adjust the pressure plate as in (c)
above; a different projector may produce
a better result
7. Broken Drive Belt
When
a drive belt breaks on a belt driven projector, the film will stop moving
but
the lamp will keep burning. If the film is not shielded from the heat of the
lamp,
some loss of film is inevitable, but you can limit the damage to a single
frame if you
are alert and shut down quickly. Replace the belt.
8. Film is Very Loose on Take Up Reel
Possible causes:
a. Badly buckled or
warped film
b. The take up sprocket is loose and feeding film irregularly to
the take up reel
c. the take up clutch is slipping.
Remedies:
a. If the take up starts to get uneven
or sloppy, you can help it along with a finger
on the reel. If the wind becomes
really floppy you will have to shut down, take the
film to the rewind bench,
mark the place on either or both reels and rewind the
floppy film back on to the
feed reel. Rewind again on to the take up reel until you
get to the place you
marked.
b. Before you rethread, check the take
up sprocket for looseness and tighten
if necessary.
NOTE: If the film is buckled you
may need to keep helping the take up reel
after restarting.
c. Use the same procedure as for (a) above. Repairing the clutch may take some
time, so it might be better to switch to another projector for the remainder of
the film.
9.
Blown Lamp or Exciter Lamp
Blowing
a lamp is an occupational hazard. It can happen at any time and there’s
not
much you can do to prevent it happening, apart from keeping a log and
changing a
lamp before its estimated lifetime runs out. But this is likely to be
wasteful,
as exciter lamps seem to keep going for ever, and it’s quite a shock
when one
decides to quit.
In
either event, shut down and replace the lamp. This won’t delay proceedings for
more than a minute or so, especially if you are at the start of the film and the
lamp
is only warm. Removing hot lamps can be a bit trickier. Never touch any
part
of a replacement lamp with your fingers. Always use a cotton glove or a
soft cloth.
Sound
a. Amplifier not
turned on
b. Amplifier not working or faulty amplifier switch
c. blown
exciter lamp
d. blown fuse.
Remedies:
b. If amplifier is switched on and
there is still no sound, the problem could require
expert attention. After
eliminating other possibilities, switch to another projector
and refer the
problem to a qualified technician.
2. Low Sound Level
Cause:
Dirty exciter lamp, lens or solar
cell.
Remedy:
Clean the exciter lamp, lens and
solar cell with a puffer and small lens brush.
These parts pick up dust and
other particles from the film and should be puffed
and brushed regularly.
3. ‘Motorboating’
Sometimes called ‘machine gunning’,
a continuous popping noise. This indicates
the exciter lamp is focused on
perforations. The film has two sets of perforations,
one along each edge. It is
silent.
4. Sound wavers or is muffled
Possible causes:
a. Exciter lamp has
passed its use by date.
b.Incorrect exciter lamp.
Remedies:
a. Replace exciter lamp.
b. Check you are using the lamp
specified for your projector. If not, replace it
with the right one.
5. ‘Wow’
Wow is caused by variations in the speed
of the film as it passes over the sound
drum. Check the pinch roller which keeps
the film pressed against the sound
drum. It may not be turning freely. Remove
the roller, and clean and lubricate
it and the shaft. While you are there,
ensure the flywheel spins freely and continues
to rotate without stopping
suddenly.
6. Sound
Especially dialogue, is out of
sync with screen image
The bottom loop is too large. Shut down
and reduce the size of the loop
to its correct proportions.