Mark Gulbrandsen

Sorry... forgot to attach the schematic!

Here is the GSMO schematic for the curious. It is not easily possible to duplicate it because of the PEC's* used, each of which contain multiple Integrated circuits. If one did built it out of discreet parts it would have to live in a separate box outside the camera. Clive Tobin is pretty much retired now and wasn't interested in getting involved in another design. But he sold me boards and schematics to one of his motors that I felt would drive the GSMO camera. Turns out that with some modifications to read the reflective CP tach sensor it does work fine. The Tobin circuit is very compact and the next stage is designing a new PCB that will allow the Tobin circuitry to fit in the same slot as the CP board did screw for screw. In addition I'll attempt to re-use the original CP footage counter if I can. It is just a simple decade counter. Tobin also uses a similar speed selector switch to what is already in the GSMO although the speed choice's are slightly different and that will require re-labeling... The Tobin board includes an overvoltage protection device which the original CP circuitry did not. It's still a ways off but I will get it done at some point this summer. I have two GSMO's myself and only one running. The Super 16 GSMO is the dead one and that one certainly needs to be running. Mark

I have acquired most of a service manual and full schematic. If any of you GSMO owners out there would like a copy just drop me a line. I am also going to send this to Ape City camera manuals as well. Mark Gulbrandsen

Over the years I have gained quite a bit of experience with crystal camera motors and Hall effect motors. I believe the result of the flicker is because of the early hall effect drive motor. These motors generally do not have overlapping pole pieces and they tend to hunt between the poles, this "hunting" area is essentially a dead point in the rotation of the motor itself. If you notice in some of the transfers posted the flicker oscillates at a slow rate... comes and goes. I believe that this is caused by a slight back oscillation into the mechanism itself from the motor hunting. Cinema Products cured this issue. Aside from adding variable speed as part of the conversion on the MIALA they also added a small high mass flywheel to the motor shaft between the motor and the inching knob. This was enough to give some kinetic energy to the motor itself and smooth out it's rotation. You'll notice that area of their converted motors is also wider and has a different cover to accommodate that flywheel. There is little kinetic energy stored in the ACL itself to help filter out this hunting between poles that the motor does. Later ACL motors do not have this flickering problem. I just bought another ACL(French) with MIALA motor and I'm anxious to see if it flickers or not. If it does I'll machine and add a small high mass flywheel myself in place of the inching knob and then shoot another test. What made me think of this? Years ago I built a VistaVision projector because I used to do a lot of location dailies. I used a Bodine Hall effect drive motor on this projector because it was 1/4 hp and would fit in the palm of your hand. It's a very light efficient little motor that Bodine sells to this day but it caused a slight back oscillation into the projector mechanism which could be heard and which was viewable with a variable speed strobe. Adding a small flywheel to the motor shaft added enough kinetic energy to overcome the hunting the motor was doing and it fixed the problem. The projector was subsequently used on a lot of films and I had zero problems with it. Anyway, this projector oscillation is no doubt similar to whats happening in the earlier ACL's. I never heard of someone with a CP motor having any flicker issues nor with the later ACL 2. Hekki's flicker problem may also have been light leaking in through the filter holder.... Always cover that thing with gaffers tape! Just my thoughts.... Mark Gulbrandsen SLC, UT

The problem with the ACL in the above post is interesting. I owned an ACL in the early 80's and it had the exact same problem. I had bought it used from a dealer and ended up returning the camera and getting an Arri SR instead. I have since bought another French built Éclair ACL and it does not have this issue. I'd still love to know what causes it. Can someone here point me towards that discussion in the Éclair forum?

I thought I'd dredge up this old topic. Since I have a pair of Super 16 GSMO's one that still works and one that doesn't I am presently building a new motor control board based on the Tobin TXM-25. Clive Tobin is in semi-retirement and didn't want to tackle another big project so I am doing it with some input from him. Because the original Tobin board is so small the new GSMO board will fit right in place of the old board and use the same mounting holes, speed switch and most likely the original CP footage counter and mounting screws. I am a couple months away from a bolt in replacement but it is happenning, the prototype is now being assembled. Also, If Ken @ Whitehouse doesn't have any magazine or shutter drive belts left then Stock Drive Products will have them. At some point I am going to start a new thread once I have the board to a presentable stage. Mark Gulbrandsen SLC, UT

I'm looking for one or two 100' GSMO magazines. If you have one you can let go of please let me know. Thanks! Mark

Am looking for a couple of GSMO 100 foot mags. Let me know what you have available... Also looking for GSMO parts and parts cameras and any other accessories you may have excess...