Film-Tech Forum ARCHIVE: What is the most versatile Zipper ?

This is topic What is the most versatile Zipper ? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jean-Michel Grin (Member # 1360) on 10-04-2003, 02:40 PM:

Past week a projectionist called me because the two changeover devices on Monee projectors was burned out.
You can see on the pic that the problem was real [Eek!]

These changeover devices, powered in 230 volts, had received a sustained voltage from a defective push-switch. You can easy guessin what hapened...

We asked to the local dealer,but no units was allvaible...
The idea came to use Kelmar changeover devices like used on Strong and Century projectors. By luck we had three units on stock an it was a relative easy job to make an adapter plate to mount the zipper onn the top of the projector, and cut a new douser plate.
You can see the result on the next pic:

I'm a bit proud of the result, for the reason I'm not a mechanical technician, But I'm wondering if exist on the market a brand of change over unit that can be fitted on most projectors, as a spare part. Kelmar change overs units seems to me the most versatile, but can someone tell me if another kind of unit are indicated ?

Thanks for Your replies, and sorry for my weak english [beer]

Posted by Mark Gulbrandsen (Member # 72) on 10-04-2003, 11:53 PM:

Actually the "MOST VERSITLE" zipper happens to be on the front of the pants you are wearing [Eek!]

! Hopefully its zipped up!

I'd vote for the Kelmar units though for all other zipper applications.
Mark @ CLACO

Posted by Paul G. Thompson (Member # 655) on 10-05-2003, 06:15 PM:

I have no use for Zipper Dousers. I hate them. They are sometimes slow and that speedometer cable they use is a joke as far as I am concerned.

The Thyde(sp), Kelmar, Weaver and the very rare dousers that Brenkert had mounted on top the BX-80's (not the Zipper) were my favorites.

Posted by Phil Hill (Member # 371) on 10-05-2003, 06:48 PM:

I agree Mark...with BOTH your statements even though I wear button-fly jeans. I have used many zippers. Ummm…changeover ones that is. [Big Grin]

The absolute worse is the Ballantyne "rotary solenoid" type.

>>> Phil

Posted by Richard Fowler (Member # 893) on 10-05-2003, 08:46 PM:

The rotary solenoid was popular in other machinery of the era when the Pro-35 was designed...I replaced many of them with a square case constant on solenoid and some converted bracketry for much less hassle and cost.

Posted by Phil Hill (Member # 371) on 10-05-2003, 09:10 PM:

That may very well be true. The bottom line is the Ballantyne implementation was a POS.

I finally designed a simple mod to their Douser PS to stop the douser from dropping in the middle of a show… IF it would even open at all without bouncing closed when activated.

It was a pain in the ass to mechanically adjust so it would work properly.

>>> Phil

Posted by Richard Fowler (Member # 893) on 10-05-2003, 09:35 PM:

I have removed many a coat hanger wire douser blade support, installed by the projectionist, from many PRO-35's [Wink]

The rotary unit looks so professional with the military grade identification sticker for such a POS. I encountered the same unit, both dampen and not, in tape transports, station loggers, telecine units I had to service where they where more at home.

Posted by Paul G. Thompson (Member # 655) on 10-05-2003, 09:55 PM:

Hmmmm...that's odd. I never had a problem with the Pro-35 douser if it was wired for constant "on" by using a maintained closure to terminal 7 & 8 of the change-over power supply. That worked just absolutely great in a single-projector system.

But yes...Phil is correct about the those things bouncing all over the place if they were pulsed. In a two projector system, they were extremely unreliable. Much of the time it'll do just as Phil said.

Posted by Robert D. LaValley (Member # 1867) on 10-05-2003, 10:11 PM:

Two projectors with cardboard, alittle duct tape, some fishing line and well placed eye hooks could work with a reel to reel theatre ...

Curtains on the port glass could work too....

Just a thought for a 5 dollar solution to change overs..

Posted by Rick Long (Member # 213) on 10-05-2003, 11:34 PM:

I have used that very solution in a few underfunded 16MM cinemas, Robert.

Biggest problem I had with the Ballantyne rotary solenoids, was either dirty contacts on the relay or a worn charging capacitor. (You really didn't need that spring in the solenoid you know, it closed just fine under gravity - with single projector systems).

Jean-Michel, great job of mechanical retrofitting there!

Posted by Phil Hill (Member # 371) on 10-06-2003, 04:39 AM:

Paul, those dousers can not be pulsed. They require current applied all the time to hold them open.

Also, as Rick mentioned, remove the rotary solenoid spring...it's useless and only serves to help the douser fail by taking and wasting valuable "holding" power.

The trick in adjusting the douser is to make sure the magnetic gap of the solenoid is full closed when the douser blade hits the mechanical stop. (That is when the solenoid is fully rotated to the closed position)

>>> Phil

Posted by Manny Knowles (Member # 1171) on 10-06-2003, 07:58 AM:

I've thought about installing curtains when we put in the larger booth windows. If there's ever a technical problem I wouldn't want folks glaring at me while I worked to get the show back on-screen.

As for the electric changeover douser, I've been very happy with the Kelmar shown in the picture above. Once in a while I've had them become a little stubborn and not want to open up but a little well-placed lube solved that. [Wink]

Posted by Paul G. Thompson (Member # 655) on 10-06-2003, 11:40 AM:

Phil, I have worked with some that were pulsed when used with the Eprad Sword equipped with the Eprad automation. (The one that had the non-sync potentiometer driven by a rack and pinion gear setup driven off the camshaft in a two-projector system.) That was 20 years ago, so I don't remember all the details.

If that was not the normal, it may have been modified by Don Jones of the Marcus Corporation. I think he may have used the pulsed relay 21-45050 to make it work. That was the problem. That pulsed relay. When they got old and flakey, they didn't work that well and the "hit" was not that positive at times because of dirty contacts in the relay.

Whatever it was, it was a total nightmare and a coat hanger was a normal piece of booth equipment to hold the damn things open.

Did you ever have the dis-pleasure of working on those things? I did not like them at all.

Posted by Gordon McLeod (Member # 33) on 10-06-2003, 03:07 PM:

I ended up building my own powersupply
I used a circuit much like the old zies autoignitor
I provided 110vdc via a large capactitor to the solinoid and a current sensing relay dropped the the 110 off to a 24vdc source once the solinoid drew current as it lifted and the big cap supplied enough to lift it the rest of the way

Posted by Phil Hill (Member # 371) on 10-06-2003, 05:46 PM:

Paul, we were discussing the stock solenoid, thus my response.

Gordon, a much simpler way is to take the stock power supply and sub a bridge rectifier to double the initial charging voltage. Then supply the coil thru a dropping resistor to supply the correct hold voltage. When you initially close the DC activation relay, about 160vdc hits the solenoid to open the douser, then the voltage drops to the hold 24-30vdc thru the series dropping resistor.

Got several hundred of these mods in operation and they work fine...many for over 15years.

>>> Phil