bolex mst motor wiring?

[milesandjules]

Hi Guys
I Just got a bolex mst motor for my h8. Now i dont have a battery for it...... is it possible to wire up a nhmi /nicad to it? I did come with a 5/6pin cord that I can hack if required I just don't know about the pin layout ect? There looks like another 2 pin plug on the back to.

Thanks
Miles

[carllooper]

I've got a Bolex MST battery here, but no documentation on it. What I could do is charge it up and see which pins are supplying what. Might take a few days. I have to get an adapter for the power supply. What I can see on the battery panel is that the output is 12 V DC. So once the pins are sorted you can use any 12V battery. The fuse on the battery is labelled: 50mA.

The two pin thing is probably for supply to a torque motor on any magazine you might be using. I assume you are not using a magazine.

Carl

[milesandjules]

Hi Carl
That would be great!

I found this page that has a pin listing.
Down the bottom of the page it shows the layout.

http://www.marriottcameras.co.uk/instru ... ctures.htm

Do they look right to you?


Ah that makes sense. those two pins at the bottom would be for the mag on the 16mm cam.

[carllooper]

Hi Carl
That would be great!

I found this page that has a pin listing.
Down the bottom of the page it shows the layout.

http://www.marriottcameras.co.uk/instru ... ctures.htm

Do they look right to you?


Ah that makes sense. those two pins at the bottom would be for the mag on the 16mm cam.

Yep, that's the battery I've got. But the power supply jack in the manual differs from that on the battery I have here. The battery here has only a four female jack rather than six, however it fits the Bolex MST motor I have here. Other than that, the battery pictured in the manual is exactly the same as the one I have here. Now your motor differs from mine. It has six pins - which is consistent with the battery manual you found. So no good me testing my pins (as assistance to you).

But on the positive side, the manual appears to have all the info you'll need. Or at least I think it does. I think the manual is saying pins 3 and 6 are a sync signal, and pin 1 is used for power plus and 4 or 5 for power minus (ground). The dedicated separate sync plug, has it's pins labelled 3 and 6, ie. the labels 3 and 6 apply to both the sync plug and power plug - which in both cases are sync signal pins.

You can try supply one way or the other on pins 1 (+) and 4 or 5(-) to see which way the motor shaft spins. Following the designated polarity should give you the right results. When facing the camera control panel, the shaft should be turning clockwise for running film forward, or when facing the motor, (as you would be for testing motor) the shaft should be, of course, turning the other way: anti-clockwise. Or at least that is the way it rotates (for forward) on a Bolex 16mm, but am not sure about 8mm. I assume it must be the same. I guess you can just try turning camera shaft by hand to see which way it should turn - look inside camera to see which way the sprocket wheel is feeding the film.

According to the manual you'll need a 12V 5A power supply. The 4A (or 5A with mag) is only at start up, after which it's either 1.4A (100ft) or 1.8A (mag).

C

[milesandjules]

Hi Carl
That all sounds like good advice. I will test it out tomorrow. I've got a hobbyking 12v 2600ma lipo battery..do ya reckon that will be ok to test it with?
thanks
miles

[carllooper]

Hi Carl
That all sounds like good advice. I will test it out tomorrow. I've got a hobbyking 12v 2600ma lipo battery..do ya reckon that will be ok to test it with?
thanks
miles

The specified battery won't have enough current: 2600 mA = 2.6A.

However you could certainly use it to test the pins on the motor. It might be enough to turn just the motor. Once the motor is turning it only needs, at most, 1.4A. If the battery is not enough to start the motor you can give the motor shaft a bit of a nudge (turn) to kickstart it (but be careful you don't hurt yourself - don't use your finger to nudge it - use a pencil or something, otherwise when it starts turning the shaft teeth can bite your finger).

Now when the motor is connected to the camera, the battery won't provide enough power to start the wheels of a loaded camera turning. Or to put it another way, the motor plus camera plus film load will provide too much resistance. There may be enough power to start the wheels of an unloaded camera turning, but probably not. According to the manual, the system (motor+camera+film load) will want to pull 4A before it starts turning, or 5A if using a magazine, which suggests the motor + camera provides a lot more resistance than the film load (as one would imagine). However, once the motor + camera + film load is turning it only needs to pull 1.4A (or 1.8A with mag) to keep it turning. It's just the initial resistance of the motor + camera + film load that will resist what the battery supplies. So in similar fashion to testing the motor on it's own you could also test the specified battery on the motor attached to an unloaded camera: just give the camera sprocket wheels a bit of a nudge (with a pencil or something) to get it started, and the motor will (should) take over.

The only remaining thing to do after that is to get a battery or power supply that provides 12V, 5A (or 12V, 4A if only using 100 ft film loads).

C

[milesandjules]

Hi Carl
Thanks for the run down on the battery amps. I will track something down on ebay that has chunkier amps.

Also have you ever tested the mst for sync sound recorded separately. If so whats it like for lip-sync ?

Thanks
Miles

[carllooper]

Hi Carl
Thanks for the run down on the battery amps. I will track something down on ebay that has chunkier amps.

Also have you ever tested the mst for sync sound recorded separately. If so whats it like for lip-sync ?

Thanks
Miles

Hi Miles.

I'm not actually using the MST (or the battery) at the moment. The MST came with a camera and it was the camera I was after. There was no battery. I eventually managed to get a battery separately, to use the MST, but not before I had put a bid on a 1:1 Tobin. I ended up with two Tobins (1:1 shaft) arriving so will be using those. The two Tobins are brand new and the last two ever made! I didn't mean to get two of them but for some reason I thought I was outbid on one and decided to go for the other that was available. The first one came with two batteries, and the second with no battery (for some reason). I already had a battery (for an 8:1 Tobin I already had) so getting a Tobin without a battery wasn't going to be a big issue. But I misread the ebay info and ended up winning both Tobins and both batteries! I've since acquired a third Bolex, so that the redundant Tobin wouldn't be lonely.

I haven't tried sync sound but definitely want to do that. For the Tobins it isn't necessary to record a sync signal as they run at crystal speed. Just a clapper board will do the trick. For the MST I'm not sure how they work in terms of sync signal. I think the idea is that you would record a sync signal coming out of the motor. The simplest idea would be to take a multi-meter to the pins and see what sort of signal you are getting (if any). You could record this signal, on the same channel you are recording sound, through an appropriate circuit that adjusted signal levels.

Or perhaps the sync signal pins are for supplying a sync signal, ie. so the motor runs at the frequency of the supplied sync signal. Don't know but would be interesting to find out.

But really, wild sync is just as easy to work with these days. Easy peasy to adjust in/out points and adjust audio length. Even pitch correction is a button click away.

For traditional sync sound and film screening (on a projector) it gets a bit more difficult. Have been working on how to do sync sound with film projection. I'd love to put a sensor inside a projector to monitor frame rate and feed this signal to a computer and humungus speakers for a big sound experience (as distinct from an optical sound experience).

C

[cameratech]

Hi Miles,

if it's a 7 pin socket on the motor the pin-out looks like this:


That's looking at the front of the motor socket or the back of the cable plug.

By itself the motor should draw less than half an amp.

You're LiPo battery should be fine to test with or use, even with a camera attached and start-up draw of potentially over 4 amps. The 2600mA figure you mentioned would be 2600mAh (milliamp-hours), the capacity of the battery. It means it can supply 2.6 amps for one hour, or 1.3 amps for 2 hrs etc. But the capacity is different from the maximum current discharge rate. Batteries can often supply several times their "C" value, or one-hour capacity. Particularly LiPos, which are often used in very high current draw applications like RC helicopters. Those things can draw well over 10 amps, which is why their batteries only last a few minutes. The maximum discharge rate might be written in the battery specs as 20C meaning they can supply up to 20 times the one hour capacity. For short bursts it can be even more. Other battery types with higher internal resistance will have lower maximum current ratings, but it's rarely as low as 1xC.

[Richard Hale]

The sync signal on the mst motor was a Pilotone signal (50 or 60 cycles) output at a recordable level to a sync track on a reel-to-reel recorder such as a Nagra or Uher. This sync signal then could be used to control the speed of the recorder synced to the Mains (50 or 60 cycles) thereby compensating for any tape slippage, stretching, etc. resulting in a correct playback at the same speed the sound was recorded at. It also could slave the recorders playback to a projector equipped with a sync pulse such as the Elmo 1200 super8 projectors.

[milesandjules]

Hi Guys
Thanks for the feed back.

Awesome wiring diagram to Dom

I was thinking the mst was better for sync compared to the old school bolex motors. I guess it would be, if we were recording with a nagra, but we will be recording to something digital.

Will have a crack at it with the lipo and let you guys know how it goes.

cheers
Miles

[Richard Hale]

The mst motor is a more stable/accurate motor than the spring motors of the Bolex. I believe it was crystal based. Recording your sound digitally without recording the mst sync signal may work. Use a clapper or something to visually/aurally reference by at the beginning and even at the end of each scene. To sync then with a NLE is a cinch. Still the camera noise will be a problem as though it can be reduced in post it is difficult to entirely omit it.

[milesandjules]

Ok it works with this wiring and battery combo Next need to test with film

Carl Let us know if ya wana sell one of those Tobin crystal motors?

Cheers
Miles