Part 2. The Basics


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, i.e. 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.


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.


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.


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.


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.


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


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.


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.


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.

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.


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. 


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.

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.


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.


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

Dirty exciter lamp, lens or solar cell.


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.


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.