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Simplex X-L

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The Simplex X-L is a 35mm projector in the Simplex line of projectors. First released in 1949, it became one of the most popular projectors in North America and remained an industry standard until the end of the first-run era. X-Ls and their later variants are known as reliable machines that require very little maintenance besides regular lubrication.

Due to the number of X-Ls in existence and the relatively maintenance-free design, they are expected to be one of the 35mm projectors with the longest service life in the digital era.


A Simplex X-L modified for hemispheric projection inside a portable dome. From the International Projectionist, Vol. 39, No. 5, May, 1964.

The Simplex X-L was first introduced in 1949 by the International Projector Corporation, and was later manufactured by General Precision, Inc., National Screen Service, and Strong International. It was rebranded as the Simplex 35 in the 1960s, and the last model for general cinema use following the traditional single lens design was the Simplex PR-1014. The X-L also served as the basis for a number of other models, including those with lens turrets, studio models capable of reverse operation, and a dual-format 35/70 projector.

The Simplex X-L replaced the Simplex E-7 and other earlier models. Some of the main improvements in the X-L include a conical shutter for improved light output, an enclosed oil bath to maintain constant lubrication of the drive system, larger 24-tooth continuous sprockets, and the option of a water-cooled gate. It was also the first Simplex to offer the option of a curved gate to improve focus stability in 1957.

The X-L was compatible with the existing Simplex SH-1000 soundhead (also called the 4 Star soundhead) and new units branded as X-L soundheads were also released. The primary distinction between X-L soundheads and the SH-1000 was an additional compartment below the exciter lamp to house a preamp. In the 1960s the X-L soundhead models were replaced by the Simplex 5 Star soundhead, which replaced the gearbox of the earlier models with a belt drive. The X-L was also designed to be compatible with soundheads manufactured by RCA and others.

The design of the X-L remained largely unchanged for decades, with few differences that would impact daily use. One notable exception is the oil gauge and filler, which was originally located on the front of the mechanism. The gauge was replaced with a sight glass inside the film compartment, and the oil filler was moved to the top of the mechanism.


35/70 Lens Barrel

A lens barrel with adjustable lateral alignment designed for 35/70 use installed on a Simplex PR-1014.

The original X-L lens barrel was fixed in place. When the dual-format 35/70 model was released, they improved the design of the lens barrel by providing a lateral adjustment to re-center the lens to the correct the centerline when alternating between 35mm and 70mm. The 35mm models can be retrofitted with this 35/70 version of the lens barrel to allow for the lateral adjustment of the lens. This is useful when switching between formats using the standard lateral alignment for optical sound and formats with an atypical lateral alignment (ex., full-frame 1.33, CinemaScope with 4-track magnetic sound, Superscope).

Drive-in Operation

Because the Simplex runs in an oil bath, the oil must pool at a low point in order to be pumped back to the top of the mechanism. On the standard indoor projector in which the mechanism was installed at a downward tilt, the oil system is designed to pump from the front of the mechanism. For drive-in installations where the projector is tilted up, a conversion kit is required to collect and pump the oil from the back of the mechanism.

Known Issues

Leaking Oil

The X-L is notorious for leaking oil. This is especially true for early models, which have a more porous casting. Later models have an improved casting and better seals, which helps mitigate the oil seepage.

Extra care must be taken when cleaning the projector to ensure that oil isn’t seeping into the operator side and pooling in the film compartment, pooling beneath the soundhead, dripping down the reel arm, or dripping onto the floor. One common solution for badly leaking X-Ls is to place a baking sheet lined with shop towels beneath the projector to collect the dripping oil.

Soundhead Pinch Roller

While it is possible to pair a Simplex picture head with a soundhead produced by another manufacturer, it is far more common for X-Ls to be paired with a Simplex soundhead that uses a rubber pinch roller to press the film against the sound drum. The rubber makes contact with the picture area and can leave marks on the film, especially when dirty.

In the platter era, some projectionists would remove the rubber so that only the film edge would make contact with the pinch roller, but that workaround cannot be used for reel-to-reel projection because it dramatically increases the time it takes to get the sound drum up to speed.


Threading diagram for the Simplex PR-1014.

For general information about threading projectors, see threading

  • Rotate the framing knob (Item 7) to its center position (FRAME reading level, as shown). Using the motor knob (SH-1000 soundhead) or the soundhead flywheel (5-Star soundhead), turn the mechanism by hand to place the intermittent sprocket (Item 9) in its rest position. In the rest position, the index mark (Item 10) will align with one of the painted white index markers on the intermittent shaft collar when stopping after sprocket rotation.
  • Open the pad roller assemblies (Items 2, 5). Open the film gate (Item 3) by moving the gate opening lever (Item 4) forward. The gate will lock in position (as shown).
  • Dismount the film gate by removing the (2) chrome knurled nuts. Use a clean, dry cloth to wipe down all film bearing surfaces of the gate and trap (Item 13). Replace the film gate and nuts. This should be performed at each threading operation.
  • Thread the film as illustrated. Engage the film on the intermittent sprocket (Item 9), and check for correct framing at the framing aperture (Item 12). When correct, close the gate by firmly holding the gate opening lever and tripping the gate release (Item 8). Walk the lever back by hand to prevent the gate from slamming into the trap with excessive force. Form loops above and below the gate as illustrated, and close the pad roller assemblies (Item 2, 5).
Intermittent sprocket on a Simplex X-L projector. Observe its range of motion and set to the center of its travel before threading. See Framing for more details.
  • Turn the mechanism by hand to advance a few frames of film. Run fingers over each sprocket (Items 1, 6, 9) to ensure that the sprocket teeth are centered in the film perforations, and the film is centered on the sprockets. Double check the position of the film in the framing aperture (Item 12). A correct frame image in the framing aperture ensures correct frame positioning in the picture aperture (Item 11). The framing knob (Item 7) can be used to correct misframes, but doing so reduces the framing range during playback. It is advisable to open the gate and rethread with the framing knob in its center position.
  • Thread the soundhead as instructed in the soundhead manual. A slight degree of film tension is required above the feed sprocket (Item 1) and below the soundhead. This prevents the film from snapping on motor start.

Framing Knob Orientation

Note that the text on the framing knob is supposed to be level when the framing mechanism is in the middle of its travel, but it is possible for the handle position to be set incorrectly.

Turning the framing knob shaft rotates the framing gear, which engages with an idler gear to rotate the framing cam, thereby rotating the intermittent to adjust the framing position. The framing knobs are connected to the shaft with through screws, so their position is fixed in relation to the framing gear. It is necessary to reset the position of the framing gear in relation to the framing cam in order to correct the knob position.

First set the framing mechanism to the center of its travel. Rotate through the entire range of motion to determine the center. Then, from the operator side, press firmly on the framing handle to compress the framing shaft friction spring until the framing gear disengages from the idler gear. Rotate until the word “Frame” reads level, and release to reengage the framing gear.


Regular Cleaning

Between each reel clean all film bearing surfaces, especially the gate and trap.

  • Remove the gate and wipe it down with a cloth. Make sure to remove any deposits on the curved runners. Remove heavy deposits with your fingernail or another soft material. Do NOT scrape it off with metal. Brush out both sides of the intermittent pad shoe. It can be hard to see dirt in this area, and cleaning it every time will prevent it from accumulating. Check for any dirt accumulation elsewhere (including inside the gate) and clean as necessary.
  • Wipe down the tension bands, and brush out the hard-to-reach surfaces of the trap, including the lateral guide rollers, taking care to clean the inboard edge of the trap where dirt is hard to see.
  • Wipe down all rollers. Hold a clean section of cloth against the roller and spin it. Repeat with a fresh section of cloth until the cloth comes up clean. Use a toothbrush on any heavy deposits.
  • Check for dirt and emulsion build-up on the sprockets, and brush them off as necessary.
  • Wipe out any accumulated oil. Check around the intermittent, at the base of the projector head where oil tends to pool, and anywhere else that oil tends to seep into the operator side.

Deep Cleaning

A Simplex X-L with the gate, trap, spot sight box, and lower rear cover removed for cleaning.

The projector should be deep cleaned on a regular basis. The frequency required will depend on factors such as the number of prints being run (and how dirty they are), the length of the time the projector sits idle between shows, and the amount of oil the projector leaks.

  • Remove the lens and aperture plate if present. Remove and clean the gate and set it aside.
  • Remove the trap. It is seated on two posts on the main main casting and held in place by a captive screw located between the framing aperture and the picture aperture. Loosen the screw, and pull the trap towards you. You can place one finger through the framing aperture for better control. With the trap removed, clean all surfaces, including the back (lamp side) of the trap. Wipe off any oil that has accumulated on the inboard end. Leave the trap out while you continue cleaning. (Note that when reinstalling the trap, you should partially open the fire shutter using the fire shutter reset button to ensure that the trap doesn’t bind against the fire shutter. Lift the fire shutter until the trap is seated on its posts and then release. After reinstalling the trap, open and close the fire shutter to ensure that it is moving freely.)
  • Remove the spot sight box. It is mounted on two shafts. On some versions, the entire upper shaft is removed, while on other versions there are removable knurled nuts on both the upper and lower shafts.
  • Remove the lower rear cover. It is held in place by three hex screws. One is located at the top of the cover (formerly hidden by the spot sight box) and the other two are at the base of the cover on the lamp side.
  • With the gate, trap, spot sight box, and lower rear cover removed, you have much greater access to the interior of the film compartment, especially the area around the intermittent. Manually advance the mechanism to rotate the shutter in order to access different areas for cleaning. Rotate the framing mechanism through its range of travel in order to reach different sections, and to access the recessed areas around the intermittent sprocket from different angles. Likewise, open and close the gate mechanism (with the gate removed) to expose different areas for cleaning.
  • For better access, it may be helpful to remove the film strippers, especially the stripper beneath the intermittent sprocket. That is a spot where dirt tends to accumulate, and it is difficult to access for cleaning. When reinstalling, make sure the stripper isn’t binding against the sprocket, but it should be close enough for the end of the stripper to be below the base of the sprocket teeth.
  • For a major cleaning, also remove the pad roller assemblies. They will be easier to clean outside of the projector, and removing them will provide much easier access to the deeper areas.
  • Clean the back of everything (sprockets, rollers, roller arms). Just because you can’t see it doesn’t mean you can’t clean it!


Pad Rollers

The eccentric shaft of an Simplex X-L pad roller.
A pad roller spring compressed with a paper clip.

Pad rollers should be checked periodically for wear, and replaced as necessary (check for flat spots or chamfering). They should spin freely without binding on the sprocket. There should be no resistance due to the build-up of dirt and oil.

There are two primary considerations when adjusting pad rollers, the depth stop between the roller and the sprocket, and the lateral play on the shaft.

Pad rollers should be set to clear the sprockets by two thicknesses of acetate film. The stops for the pad roller arms consist of an adjusting screw that serves as a depth stop, and a nut to lock the adjusting screw in place. On each pad roller arm, one of the roller shafts is straight, and the other is eccentric. To make the adjustment, first loosen the set screw on the inboard end of the eccentric shaft and rotate it so that the eccentric roller is as far from the sprocket as possible, then adjust the stop so that the roller on the straight shaft is two film thicknesses from the sprocket. Tighten the lock nut, then rotate the eccentric shaft until that roller is also two film thicknesses from the sprocket, and tighten the eccentric shaft set screw.

When setting the lateral position of the roller on the shaft, it should be set with the minimum amount of play required for the roller to spin freely when lowered towards the sprocket. It may be necessary to shim the roller with washers on the inboard end. On the straight shaft the lateral position of the entire shaft is adjusted. On the eccentric shaft, the position of the knurled handle sets the lateral position of the roller.

Pad rollers should be removed periodically for cleaning. Remove the roller, clean and remove any corrosion from the shaft, and clean the interior and exterior of the roller. This should be done whenever resistance is felt when spinning the rollers, or at least once a year. There are some variations in pad roller shaft design, but typically for the straight shaft, the entire shaft is removed by loosening the set screw on the pad roller arm. Be careful not to lose any washers that are in place to shim the roller away from the arm. The eccentric shaft has a knurled handle on the outboard end that is usually held in place by a set screw, although in some cases the handle is threaded onto the shaft. For either design, remove the knurled handle in order to remove the roller without affecting the eccentric adjustment.

Be careful not to overtighten any of the set screws, since this can mar the shaft. On the inboard side, this can make it difficult to remove or insert the shaft, and on the outboard side it can create a burr that scratches the inner diameter of the roller.

In dry climates, plastic rollers may be run dry. In climates where humidity is a concern, a small amount of silicone spray can be applied to the roller shafts to prevent corrosion. Spray it onto a cloth, wipe down the shaft, and remove any excess. Do not use oil to lubricate plastic rollers.

For better access to the lower pad roller assembly, remove the spot sight box and the lower rear cover.

Removing Pad Roller Assemblies

To remove the pad roller assemblies entirely, first relieve the tension on the springs. Rotate the assembly to compress the spring. It will be fully compressed shortly before the assembly is in the full open position. There is a hole in one leg of the forked spring guide, which will be revealed when the spring is fully compressed. Insert a paper clip through the hole to relieve the spring tension. This will keep the spring compressed when removing the assembly. Remove the screw and washer holding the pad roller arm against the main casting, and carefully walk the assembly out, ensuring that the clip does not fall out of the hole in the spring guide. After the spring clears the guide pin, remove it before removing the rest of the assembly.

If you lose control of the spring and it comes apart, it may be possible to recompress the spring using the film slot on the main casting. On X-Ls with a narrow film slot at the top of the head, place the spring assembly on the outboard edge of the casting with the solid leg of the fork in the film slot, and the leg of the fork with the pinhole slightly overshooting the outboard edge of the projector head. Compress the spring and pass a pin through the hole.

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