Pentax MX Mirror Box Mechanism Disassembly

Remove the lever cap. The cap is reverse threaded.

Lift off the advance lever.

Remove the collar beneath the lever.

Set the ISO to 100 and the shutter speed to 1000.

Remove one pin head screw.

Lift off shutter speed dial.

Remove the collar beneath the dial.

Installation Notes: Make sure that the tab on the shutter speed resistor mates properly with this slot on the shutter speed dial.

Place a tool in the fork of the rewind shaft. Turn the rewind knob counterclockwise to loosen it.

Remove the lock ring underneath the rewind knob.

Remove the cover plate.

Remove two M1.7 x 3.2 mm screws.

Remove two M1.7 x 2 mm countersunk screws.

Lift off top cover.

The release cable pin in the shutter button is loose and may fall out.

Apply isopropyl alcohol to soften the leatherette adhesive.

Turn the self-timer lever to the charged position.

Peel the leatherette off the camera body, carefully working it over the self-timer lever.

Remove one loose cover panel.

Repeat for the opposite panel.

Unsolder two yellow wires for the aperture resistor.

Remove four M1.9 x 3.9 mm screws.

Lift off front board.

Look for shim washers at the screw locations and note their positions.

Remove three M1.7 x 2.0 mm countersunk screws.

Lift off bottom cover.

Remove loose plastic housing for motor drive contacts.

Remove four M1.9 x 3.8 mm screws.

Lift off lens mount baffle.

Use isopropyl alcohol to soften adhesive and detach wires from the backside of the baffle.

Unsolder two brown wires for the shutter speed resistor.

Unsolder one gray for the x-sync.

Unsolder one white wire for the FP sync.

Unsolder one green wire for the motor drive connection.

Unsolder one blue wire for the LED switch.

Unsolder one red wire and one black wire.

Open up wire routing guides and remove all wires from them.

Pull the black and red wires out of the hole in the bottom of the chassis.

Make sure the gray wire is free and can pull away with the mirror box.

Remove one M1.4 x 2.8 mm screw and washer.

Remove one M1.7 x 2.8 mm screw.

Pull the LED PCB out of the side of the mirror box.

Loosen the slotted post but do not remove.

Slide the idler gear back so that it no longer engages with the speed indicator disc.

Remove two M1.7 x 4.6 mm screws.

Remove two slotted posts.

Lift the mirror box up and tilt the top forward to remove it.

Temporarily install the wind lever and the shutter speed dial.

Wind the camera.

Press the shutter release button.

Release the opening curtain latch. This is usually done by the mirror box but has to be done manually in this case.

The mirror release latch should move freely and snap back to its home position.

Push up on the post to activate the depth of field preview function.

To charge the mirror, push the post on the bottom of the mirror box forward.

Push the mirror release latch down to flip up the mirror.

Push the mirror return latch rearward to flip the mirror down.

LED Switch (blue wire) and FP flash sync (white wire) should be open when the mirror is down and close when the mirror is up.

See Pentax MX Viewfinder Disassembly for instructions.

Remove two screws.

Look for shim washer under the mounting plate.

Remove one M2 circlip and shim washer.

Note the position of the bias spring for reassembly.

Remove mirror release latch.

Remove shim washer.

Remove two M1.4 x 3.4mm screws.

Remove upper mirror actuation lever.

Remove loose plastic bushing. This may stick to the actuation lever.

Installation Notes: Make sure that the actuation levers are properly coupled with the charge levers on the bottom of the mirror box.

Remove the lower mirror actuation lever.

Remove shim washer.

Installation Notes: Make sure the bias spring is properly placed.

Remove one M2 circlip.

Remove shim washer.

Remove mirror lifting lever.

Remove two M1.7 x 2.4mm screws.

Remove LED switch contact.

Remove two M1.7 x 2.4mm screws.

Remove FP sync contact.

Remove one M1.4 x 3.3 mm screw.

Remove mirror return latch.

Remove bias spring and shim washer.

Remove two M1.7 circlips.

Lift off air damper.

Detach and remove mirror lifting spring.

Detach mirror return spring.

Remove lever screw using a spanner wrench. The return spring may still have some tension in it.

Lift off mirror return lever.

Remove shim washers.

This piece of foam is used to silence the coil spring. It can be replaced or removed. If removed, a small piece of heat shrink placed around the coil spring can act as a silencer.

Remove mirror lifting lever.

Clean all shafts on the mirror box with isopropyl alcohol. Remove any other visible grease.

Clean all levers and mechanism parts especially the pivots.

Lubrication for the mirror box mechanism is minimal. No oil is recommended.

A heavy molybdenum grease should be used on high friction latching points to reduce wear.

This is also a good time to replace the mirror bumper foam.