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I - DESCRIPTION A. GENERAL DESCRIPTION The Polaroid Land SX-70 is a folding, pocket The four element lens has a maximum aperture sized, single-lens reflex camera which takes of f/8, and a focusing rang from 10,4 inches to and immediately delivers full-color pictures infinity. The shutter is automatically controlled approximately 31/4 inches square (see figures by a photocell and electronic timing. Electrical to 1-1, 1-2 and 1-3). Operation is automatic; the mechanical energy conversion is ac
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Figure 1-3 Opened for picture taking The subject is viewed and focused throught the cycle to prepare for the next exposure. Following taking lens, a mirror, a Fresnel viewing screen thenth exposure, the flash circuit is inhibited until (with spilt-image focusing aid) and a optical a fresh film is inserted. Normal operation will system to focus the image at the viewing eye- resume when the camera is reloaded. piece. As in all single-lens reflex cameras, the shutter must be open to provide
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When the camera is fully opened, the interlock 2. Loading the Film pack switch (S6), located at the left rear corner of The front coverlatchis located on the right side the mirror cover, is closed and the battery is of the camera just inside the rim of the bottom cover assembly. Pressing down on this yellow connected to the camera electrical circuit. (Figure 1-4). latch releases the front cover which drops down to expose the film chamber. With the cover open, a film pack can be inserted or
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Gears in the front cover must engage the main front edge of the front cover. The camera is now gear train of the camera before the gear train ready to take the first picture. is put into motion. A switch (S7) located in the forward section of the gear train compartment initiates the application of power to the gear 4. Setting the exposure counter train drive motor. Switch (S7) is actuated by two When a used film pack is removed from the film components chamber, the action automatically res
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Figure 1-8 Viewing and shooting shutter to initiate a series of events. The shutter The shutter opens and closes to perform the blades close to cut off the optical path. The exposure function. hinged Fresnel viewing screen is swung upward and comes to rest in front of the fixed viewing A first-surfaced taking mirror is fastened to mirror (Figure 1-8 B). the underside of the Fresnel carrier assembly.
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The image is reflected by the mirror onto the slide. The counter will start at number 10. Since film surface. the electronic metering system switches S8 and S9 are physically attached to determinesthe required exposure, and programs the counter, the camera will cycle through 10 the shutter opening and duration accordingly. exposures even though there be less than 10 sheets of film in the pack. This deviation must be The incorporation of a mirror in tghe lens-to-film recognized whenever a pa
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Figure 1-9 Inserting the flash bar 10. Closing the camera specially shaped cutouts, open the lens from a When through using camera it be can folded and totally closed position to a suitable aperture. The latched in its closed configuration by pushing two blades then reverse direction and again shut the erecting link. When the camera is closed, off the optical path. These same two blades also the interlock switch (S6) is opened so that the contain a similar (although differently shaped)
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When the release button is pressed, a switch When the solenoid has reached the end of its S1 closes (Figure 1-11 A and B) and applies stroke (shutter closed, it no longer requires operating power to the shutter. As soon as power maximum current to hold it at that postion. is applied to the shutter, solenoid #1 is energized Switch S4 (located on solenoid #1) closes (CB) and rapidly moves the shutter blades to the and activates an electronic circuit called the closed position. POWER DOWN CIRC
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to an adequate level to hold the solenoid after the motion of the blades is such that all of the factors high-current circuit has completed the solenoid involved are continously variable throughout the operating function and switches on the motor exposure period. this fact, however, is a design drive circuit. Thus, the shutter will remain closed, consideration and should not confuse the theory with minimum battery drain. of the shutter operation from a maintenance point of view. Light enter
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mechanical device identified as the interceptor When the flash delay period reaches completion, connected to the lens focusing mecchanism the circuitry removes the holding current from (Figure 1-13 A). the interceptor is moved as solenoid #2. Since the solenoid is an electro- the lens is focused regardless of whether mechanical device, removing power from it ambient-light or flash pictures are being taken. causes a collapsing magnetic field which induces When flash bar is in place (S2 close
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Figure 1-13 B Interceptor link, Solenoid 2, S2 operation - Solenoid energized Figure 1-14 S5 being opened by the recock ram (Gear train)
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In cameras with «P» configuration or later shutter there is no ambient light measurement made. If a flash bar is in the shutter socket a flash picture will result regardless of the ambient light level. On early cameras, an ambient light measurement is made during the flash delay period. Since the photocell aperture is a part of the shutter blades, the amount of reflected light reaching the cell will also be a function of focusing distance. the shutter electronics delays firing the flash
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II - THEORY OF OPERATION A. INTRODUCTION A general description of the camera and the The battery has adequate capacity to expose sequence of its functions is contained in all 10 film frames with at least six months of Section I. In that section, detailed analysis of expected shelf life. individual assemblies and electrical circuits was minimized so that emphasis could be placed on C. LENS the intenelation-ship of various functions. In the following paragraphs, the individual groups of The
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Figure 2-2 Viewfinder optics (exposing) the subject passes through the camera lens and 1. Fresnel (Figures 2-3 A and 2-3 B) is reflected by the viewing mirror (on the inside The special Fresnel (pronouced Freh-nell) screen is employed to enhance the viewing surface of the mirror cover) to the Fresnel viewing screen. image by increasing the brightness and defintion. If a matte white surface were substituted for the The entire subject image is now reproduced Fresnel screen, an image would
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The screen itself is a sheet of plastic upon which increases the brilliance of the image within teh are impressed series of concentric rings much like viewing aera. the grooves pressed into a phonograph record (Figure 2-3) instead of having a vee shaping; In summary, the Fresnel satisfies three conditons: however, the grooves in the Fresnel screen form 1 - it enhances focusing by distributing light rays a saw-tooth with a tooth angle increasing slightly evenly across the entire viewing aera.
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2. Viewfinder mirror, the 6-edges viewing mirror is used in the The viewfinder optics consist of an eye lens, a optical path twice. First, the light rays entering concave mirror and a wafer lens (Figure 2-4). As the camera from the taking lens are reflected in all simple optical system, a certain amount of onto the Fresnel screen by the viewing mirror. distortion is inherent in this design. A small wafer Secondly, the operator views the image on the lens is introduced into the viewfinder
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The entire ECM (rather tna its individual b- Switch S2 places the circuitry into the flash integrated circuits) is used as a remplacement mode. Switch S2 si closed when the flash bar item. For that reason, the theory of operation and is inserted into the FFA on the top of the shutter analysis techniques presented in this manual housing. It commands the integrated circuit have prepared in such a way that the repairman in the FFA to select the first unused flashbulb can relate a specific came
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c- Switch S3, normally closed at the begining NOTE : Whenever the SX-70 shutter is discussed, of the exposure cycle is opened by the recock it must be noted that, since the camera is a single ram located in the gear train assembly. See lens reflex and focusing is accomplished through Figure 2-7. As the exposure sequence begins, the taking lens, the shutter’s normal state si open, S3 opens and actuates a delay circuit (Y delay) not closed as in other Polaroid cameras. in the EMC which retards
