How to disassemble a SX-70 Camera

This article is work in progress.
I am going to describe the sections in more detail in the future.
Don't blame me if you damage your camera following my instructions.
The pictures were done on heavily outdated (+2years) SX-70 film, so their quality is not as you could expect it from a SX-70 with new film.
Thanks to Chris Czopek for providing some cameras for research.

Tools

Get a service-manual.
There are PDFs of the SX-70 service manual and the Sonar supplement for it floating around on the internet.
Some people sell them but if you look around you will find them for free.

You will need a Torx T4 or 1mm square (Robertson) screwdriver.
Some cameras also require Torx T5 or square section screw drivers, but I didn't encounter any of these yet.
Don't even think of opening the screws with a blade or a hex screwdriver, you will ruin the screws and eventually the tool.
Good tool dealers will sell you a T4.
Others will tell you that the smallest Torx size that exists is T5 (!). A paper clip bent to L-shape is useful to push the pins out.
Pliers to hold the Paper clip.

Most of the screws and pins in different places are slightly different in shape /size.
It is recommended to note the position of each screw so you can put them back in the right places. I stuck them with adhesive tape on a sheet of paper and wrote the place of origin next to each.

The SX-70 and its sections:


A: Main Body
B: Roller assembly
C: Shutter assembly
D: View finder
E: Bellows

A: The Main Body

Carefully peel the leather off the big bottom piece.
If it is real leather, there is a sheet of aluminium foil under it that you should peel of together with the leather.
The glue is strong, be careful not to stretch/wrinkle/dent the aluminium foil.
If the camera is covered with plastic "Porvair" then it is likely that you will tear the cover.
Under the cover there are four screws that hold the bottom shell in place.
Two holes give you access to the battery contacts.
Remove the screws and take the bottom shell off.

B: The Roller Assembly


The roller assembly is the part that folds down when you load a film pack.
It contains the two rollers that develop the film, the sheet metal spring at the bottom where the photos are ejected and a light shield (The flap with the name of the camera on it).
Dirty rollers will lead to spots repetitive patterns on the pictures. A bent output spring will let some light in that ruins the pictures.
Never peel off the leather from the roller Assembly. It is glued to the output spring and the spring will bend before the leather comes loose. To remove the roller assembly simply push the hinges inward to release them from their bolts and unhook the whole assembly.

C: The Shutter housing (regular as well as Sonar models)

This section was written by Marty Kuhn

The printed circuit board on the rear of the shutter assembly is the "brains" of the camera.

To remove it, carefully unsolder the flex cable and the connections to the flash- and solenoid units.
My guess is that the resistor and capacitor on the pc board are the key elements of the integrator that collects the photo current during exposure.
If this is true the value of the capacitor should be proportional to 1/film speed. Changing the value of C to 150 pF should set the camera to 600 ASA for 600 film. (I haven't tried this yet).

D: The viewfinder Assembly

The viewfinder and the part of the shell where it is mounted are fastened with pins that act as hinges to the cameras folding mechanism.
To unmount the Viewfinder unfold the camera and take the shutter cover off. (see above)

Push the two pins outward with a paper clip bent to L-shape. Note that the two pins have different lengths, but it is obvious which goes where.

Flip the whole assembly up and

push the two pins out that connect the assembly with the shutter assembly.

E: removing the Bellows

remove the two screws that connect the bellows to the shutter-base two that attach the bellows to the front plate where the shutter sits (remove shutter first)

unhook the two latches on the rear on either side that hold the bellows down
(You may have to unscrew the gear (3 screws)to access the right hand latch, but I am not sure of that.)


To remove the bellows-assembly, push out two pins in the rear unhook the strut.

Gear

If the Gear is jammed, you can partially inspect it without disassembling the camera.
Pry off the plastic gear cover, start at both sides of the release-button for the film- door.

The Gear contains electrical contacts.

Miscellaneous

I still have not found a way to unsolder the camera's flexible printed circuit board without having it separate in three layers.

Here is a picture uf a SX-70 with its clothes off:

The chassis with the swinging mirror

The fresnel-side of the swinging mirror.

More shots of the naked SX-70: