These pictures may help you bringing the Speed Graphic Focal Plane Shutter back to life again.
Unnecessary to say, but please remove lens and Graflok back including ground glass. Close the camera.
Set the selector slide next to the flash contact post on the side cover on Back position.
Make sure the focal plane shutter is in O open position.
Remove the camera back. The top screws are the little ones. 3 longer screws on the bottom side. One wood screw No. 3
To remove the side cover plate. Unscrew 1 and 2. The upper two screws are wood screws. The other 4 are metric screws. While holding the winding key straight, the plate cover can be slipped over the winding key.
The spring which pulls the focal plane down is hidden in the shaft. The shaft is hold in this position by the tension shaft retainer b. The retainer screw a holds the shaft retainer in position. Now by unscrewing a, while at the same time holding b with your left hand fingers in position, you may turn the spring loaded shaft a few turns anti clockwise.
Having done that replace screw a back in position. Now put one drop of oil on top mechanism plate. One drop on a small screw driver to get it into position on the top and bottom roller shaft and maybe one on retarder d. Check the working with the governor c. Now try the good working of the focal plane shutter by winding the key and releasing the shutter in all the exposure times. The focal plane shutter should work without hesitations. If possible check the working with the electronic tester.
Clean contacts as shown on next photos. Be very carefully as these are very fine metallic parts. Do not forget the contacts on the focal plane shutter. There are more than one.
Unscrew one of the two receptacle contacts on the backside of the plate cover. Meanwhile the other holds the washer in the correct position.
Clean the contact with Scotch Brite and replace the stud receptacle contact. Now clean the other one.
If the Spring shaft retainer jumps off.
This procedure needs a bit of feeling. Once the screw has been removed, the retainer wants to turn back to relieve the tension of the spring. If this should happen, do not panic.
The focal plane shutter is still in "O" open position. Press the build in shutter release knob on the front of the camera. Under normal condition the curtain would come down, but the spring is not loaded. By turning the retainer anti clockwise, the curtain will move slowly downwards. If the curtain arrives at the bottom, give the spring shaft some 4 more turns and replace the retainer screw a again. Turn with the winding key the focal plane shutter in "O" position and press the release button. The curtain should come down fast. Lets say at 1/15 sec. If not repeat the procedure by giving the shaft 2 more turns. Repeat this until you are satisfied about the exposure speed.
Warning: do not force the spring too much. These springs are some 50 years old.
I did this adjustment some dozen times and never broke a spring, but I know that some of my readers were not so lucky.
Now carefully try the other exposure times. If the spring asks too much power to turn the winding key in the next position, it should be taken as a warning that the spring tension is too high.