McLarenblog

Arriflex motor for the S camera which uses a large power transistor on the side of the motor.

Complaint: motor would race in speed.

Repair: The motor must float electronically and therefore can not touch the case. There are four screws holding the transistor in its holder assembly. Make sure that each of the screws are not touching the transistor body. I had to place a very short piece of spaghetti along the screw shaft where it might come into contact with the transistor. I used only two spaghetti pieces on to the screws that actually reach the camera body. The other two screws only reach the base plate and can therefore touch the transistor.

Please understand that the mounting block for the transistor is composed of three plates. There is a large non conductive block on which the transistor rests. Over that transistor is a metal, conductive plate. The top plate is non conductive.

A real quick fix is to loosen the four screws and center the transistor so the two screw mounting holes that might touch the mounting screws will not touch. Loosen just enough so you can take a small tool and tap the transistor in proper place. Then tighten the four screws down snug. An ohm meter can be used to read from the screw to the transistor body. You should not read below 4ohms on the two screws that reach the main motor housing. The two screws that do not reach the main motor housing will read as a direct short which is normal.

The information here is for educational and reference use only. Decide on your own how to proceed in performing any repair you face. We do not accept any responsibility for this information being entirely accurate. We hope it is accurate. Most of the information posed here has been noted to be significant, used in the repair process, and to some extent tested for accuracy through the actual discovery and recording of performing a repair. If you decide to use any of the information here, try to keep in mind that a number of factors may change when you attempt the “same” repair. Models do change from apparently being same units. Their are definitely different methods of making a repair. The steps that you should use to achieve a successful and expedient repair might be different. The problem you face with a piece of equipment might be similar but not an exact match to what we faced. Just use common sense and always be a bit skeptical of following our methodology until you feel that you and we share the same viewpoint and tactics.