Chapter
4.
Troubleshooting
The most valuable assistance you will ever get is from an experienced technician who has 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.
Getting
the film ready
1.
Inside out film
Film
that is wound inside out, ie with the perforations on the wrong (far) edge of
the film when you load the reel on to projector’s feed spindle, should be
rewound on the rewind bench.
Put
the loaded reel on the feed spindle so that it comes 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.
Threading
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
Possible causes: (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
(b) Repair with full width tape or
perforation repair tape. If damage cannot be repaired, 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.
Chatter
(or clatter) is an indication that the projector is having trouble. Be ready to
shut down and reset the loops.
Resetting
the bottom 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.
If
you have to shut down, you don’t need to 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.
If
the problem recurs, you may have to unthread and 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.
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; (e) Throw is too long; (f) Wrong lamp; (g) 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.
(f) Replace the lamp.
(g) 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 edges
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.
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.
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.
Fortunately
lamps don’t blow very often, and when they do it is mostly at startup. 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
1. No sound
Possible causes: (a) Amplifier not
turned on (b) Amplifier not working or faulty amplifier switch, (c) blown
exciter lamp, (d) blown fuse.
Remedies:
(a) Switch amplifier on.
(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.
(c) Check exciter lamp and replace if
necessary.
(d) Check fuse and replace if necessary.
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.
