How to Remove the TL-DTL Top Plate
The service procedure described here for basic top- and bottom-plate disassembly is equally applicable to all Mamiya 500- and 1000-TL and DTL cameras. Please read carefully in its entirety before proceeding to disassemble your camera. We cannot be responsible for damages you might incur by working on your own equipment.



Begin Disassembly by unscrewing the left-hand thread (clockwise is off) rewind button on the bottom of the camera. Next, take out the four bottom cover-retaining screws and lift off the bottom cover. If the S-76 battery is still in place, remove it from the camera.

Figure 1 - BOTTOM OF CAMERA

Figure 1 shows the bottom of the camera body with the bottom plate removed. Note the wind lever axis and the wind lever return spring, which hooks to the left side of the lug on the wind lever shaft, and to the right side of the diaphragm-meter switch link. The meter shutoff button shaft and lever pass through the middle of the wind lever shaft. One end of the meter shutoff button shaft lever rests against the diaphragm-meter switch link, and the other end hooks to a flat, tension-type spring, which itself hooks to a stud screw in the camera body.

Pull the wind lever away from the camera body, and watch the shutoff-button lever fall between the wind lever shaft lug and the diaphragm-meter switch link. Push the wind lever back against the camera body, and note that the diaphragm-meter switch link is pushed across the camera body, closing the contact on the battery-holder for the exposure meter. At the same time, the diaphragm striker plate is pushed forward inside of the mirror cage to stop-down the diaphragm of the lens.

A common problem with this camera series is the exposure meter switch. Always check the battery and then the switch in the bottom of the camera when you have a meter problem. Many times the tab on the battery holder will break off, preventing the switch link from making contact. Some of the newer models of the series (later in the production cycle) have a spring tab on the end of the switch link, to ease the pressure on the battery holder itself. Models after 1973 have a switch near the wind shaft, which was meant to eliminate the meter switch problems.

The Mamiya-Sekor TL-series provides both X and FP synch via twin contacts. The FP contact is closed via the opening curtain latch, which is tripped by a linkage on the mirror cage approximately 7- to 15-milliseconds before the curtain clears the opening side of the film plane. The X contact is closed via a cam and insulated stud on the bottom of the opening curtain drum. The contact is closed only as soon as the opening curtain complets its travel across the film plane.

Note that the FP contact is closed only as long as the mirror is in the "up" position. The X contact is closed when the shutter is tripped. Thus, the FP contact acts as a safety switch, allowing continuity in the sync circuit only while the shutter and mirror are in operation during an exposure. Failure of the FP contact will also render the x sync circuit inoperative. So handle with care, as the sync contacts bend easily.

    Figure 1a - FLAT TENSION SPRING

To continue disassembly, remove the flat tension spring (Figure 1a) from the bottom of the meter shutoff button shaft and lever. This spring provides the upward pressure on the shutoff button shaft, and allows the shutoff button lever to drop between the wind lever lug and the diaphragm-meter switch link when the wind lever is pulled away from the camera body.

Figure 2 - TOP OF CAMERA BODY

Carefully pull the meter shut-off button shaft and lever out of the camera body approximately 1/4-inch. This will allow the meter shutoff button to drop free from the top of the wind lever. Push the meter shutoff button shaft back into the camera body, and reconnect its spring (if it becomes disconnected during this procedure).

On the under side of the meter shutoff button you will find an access hole. There are repair descriptions (and even repair facilities) that will try to short-cut this step, but they inevitably damage the top of the wind lever, the meter shutoff button, and the camera's top plate, all because they are too lazy to remove the bottom cover and do this right! Loosen the set-screw in the wind lever cap and unscrew the left-hand threaded (right is off) wind cap.


Set the shutter speed dial to 1/4 second, and the ASA (ISO) to 80. Loosen the set screws now visible on the rear of the shutter speed dial. Reset the ASA to the highest setting, and speed dial to Bulb (B). Lift off the shutter speed dial. Removing the dial in this position allows most of the tension to be released from the exposure meter spring, and prevents meter backlash when the dial is removed.

Wedge the rewind fork with a small screwdriver, and unscrew the rewind knob. Remove the three screws from the top cover plate -- one at each end and one under the speed dial. Lift off the top cover and the washers from the top of the counter and shutter release button. Using a pair of delicate pliers, carefully unhook the prism hold-down spring. Lift off the plastic cover, prism and prism seat shim (this shim is not found on all Mamiya TL- and DTL-series cameras). Remove the two screws in the lens mount apron and lift it off.

You have now completed the basic disassembly of the top and bottom plates. Figure 2 shows how the top of the camera body looks at this point (a better picture will be provided soon).

When re-installing the speed dial after your work is done, simply set the shutter speed to Bulb (B), and rotate the chain coupler all the way counter-clockwise. Set the speed dial to ASA 800 (or the highest ASA), and set the dial back on the camera body with the Bulb position to the rear of the body. Rotate the speed dial counter-clockwise, and pick up the chain coupler. Finally, seat the speed dial in the Bulb position. Make certain the set-screw is very tight, or the speed dial will come off as soon as you try to reset the ASA!

This procedure applies to all TL- and DTL-series Mamiya cameras.