Adjusting Shutter and Pulldown Timing on Bolex REX 5

[Alexander Boyd]

I'm looking for some guidance/tips on how to adjust the shutter and pulldown timing on a Bolex REX 5. 

Running it via the motor, once I let go of the run-/start-button the shutter stops in an open position (fully retracted), leaving the negative exposed. 

I did the test often mentioned here, marking the film and moving it manually. Film does not move, hence shutter and pulldown seem to be in synch relatively to each other. But would be nice to learn how to adjust the pulldown timing too, just in case.

Thank you in advance for your help!

[Simon Wyss]

There’s a little more to the timing of an H than only the claw-shutter cooperation. But I take that you won’t or haven’t disassemble/d the whole mechanism down to the mainspring, so you have just shutter and claw to adjust. If I may keep it simple, see that the mechanism is halted by the derailleur under force from the mainspring. Then lift the Nylon gear and set the claw gear so that the excentric post is in the lowest position. Put on the plastic gear while aligning it with its two bores parallel/perpendicular to the square lug of the 1-1 shaft. Put on drive cup to sit on the square and secure with screw.

Next you put on the front section with the shutter in a position where both blades cover the aperture. Make sure both claws are turned back against their rests. Slowly lower the front and observe shutter, turret swivelled 180 degrees, reflex double prism swung out. Shutter should not turn far. Once in place, hold it there while pushing the side release knob to P(ICTURE), the single-frame functions switch set at T(IME). Shutter should stop with leading edge just above aperture, Paillard specified 1,5 mm. If not, repeat sequence until you’re near. If unsatisfactory, loosen the three set screws of the helical gear on shutter shaft, turn about 20 degrees, retighten.

When like described turn in the front attaching screws, one may be the clamp with a nut on the inside. Before tightening the screws observe shutter while holding side release pushed to P and wiggling the front in the little room the screws allow. If still satisfactory, tighten all screws.

To check set camera up, turn spring clutch lever to 0, at the same time lock side release at M(OTOR). Put rewind crank on 8-1 shaft (the one in axis with the frame counter’s singles knob) or on 1-1 shaft in case you have a straight pin in it. A RX-5 usually has the asymmetric hammer pin there for the synch motors. Pressure unit removed from camera and turret free observe cooperation between claw and shutter. That’s all.

Edited October 17, 2024 by Simon Wyss

[Alexander Boyd]

This is amazing, thank you so much Simon. I was actually considering sending the camera to you, but it looks like you no longer take in cameras for this year anymore?

[Don H Marks]

Last time I had my square-bottom H8-Rex apart was 2003, and I did not have a digital camera for documentation. So I also need a refresher on this before I do the next CLA. 

Correct me if I'm wrong. From what I recall, if the conditions of the gears for the claws are met per the service manual (and as you described above), then it is just a matter of trial and error to re-fit the helical gear back in place to mesh in the correct position (assuming it was timed correctly in the first place and the pinion has not been removed and replaced). 

 

Edited October 17, 2024 by Don H Marks