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Author Topic: What would cause a dowser to slowly slip down? Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 12-22-2005 01:23 PM                        This happened for the first time last night: I was watching the film and suddenly I noticed the picture getting dim towards the bottom. At first I thought it was part of the movie (as it was a dark scene), but then it became evident after a scene change that something was amiss. I glanced around and couldn't find anything. It kept getting worse and finally I saw that the dowser was slipping down and cutting off the light. I manually closed it and opened it back up... problem solved. What would cause a dowser to slowly creep down like that? It's controlled by a Simplex electric changeover which has worked like a champ. After reopening the shutter, I kept an eye on the changeover to see if I could notice any movement in the operating rod that would indicate a problem... nothing. The problem didn't reoccur, but this happened towards the end of our final movie, so I haven't had a lot of time to test it. Any suggestions on what may have caused this? Should I tighten the speed adjustment screw to be safe?  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 12-22-2005 02:06 PM                     A little more information would be helpful. Is it a Simplex C/O or another brand such as Weaver or Zipper? Are you working with automation or doing changeovers? What type head are you using? The guys here are pretty darn good at nailing a trouble but the more they have to work with the better. My first impression though is see if it happens again. After all, "if it ain't broke, don't fix it".  |  IP: Logged Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 12-22-2005 02:14 PM                        quote: Dan Chilton It's controlled by a Simplex electric changeover No automation... manual changeover. Simplex XL projector.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 12-22-2005 02:37 PM                        What type of changeover--Kelmar, Essanay (zipper), or Weaver? I've seen Essanays that said "Simplex" on them, but I've never heard of a Simplex-brand changeover (maybe someone else has).  |  IP: Logged Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 12-22-2005 03:01 PM                        Scott, you're right: it's an Essanny SA5 (117 A.C.) UPDATE: Yep, it's definitely a problem. Upon opening the dowser, it starts to slide down a fairly good clip. I'd say, if left unattended, it would go from being fully open to fully closed in a little less than 3 minutes. I have a trusty rubber band and pair of vice grips holding it open right now. Any suggestions? [ 12-22-2005, 04:50 PM: Message edited by: Dan Chilton ]  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 12-22-2005 04:45 PM                     If I remember correctly, Zippers don't remain powered after the change-over is activated; e.g., there is no holding current. Therefore, I'd check to be sure the couplings are secure on the dowser itself. If allowed to vibrate, it might just cause the dowser creep you describe.  |  IP: Logged Sean Goodrich Film Handler Posts: 22 From: Dallas, TX, USA Registered: May 2000 posted 12-22-2005 04:50 PM                     Is there a screw on the top of the dowser? Try tightening that. Sometimes if it's too loose the shaft bounces back when it opens.  |  IP: Logged Andrew McCrea Jedi Master Film Handler Posts: 645 From: Winnipeg, Manitoba, Canada Registered: Nov 2000 posted 12-22-2005 04:56 PM                        Just out of curiousity, what is a changeover? I always thought that it was the same thing as a douser...  |  IP: Logged Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 12-22-2005 05:02 PM                        I was under the impression that a changeover was the mechanism that automatically dropped the dowser of one projector and lifted it on another during a "changeover." I could be wrong, but that's what it's referred to as in the Simplex parts catalog. As for my malfunctioning changeover, I'll tighten the speed adjusting nut and see if that fixes anything. Wish me luck! UPDATE: I tightened it a bit, but the dowser is still slipping. I didn't get a chance to tighten the lock, just the adjusting nut. I'm going to wait until the movie ends to fiddle around with it.  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 12-22-2005 06:07 PM                     quote: Dan Chilton I was under the impression that a changeover was the mechanism that automatically dropped the dowser of one projector and lifted it on another during a "changeover." You are correct. The mechanism is a 2-winding push-pull type solenoid where winding # 1 is used to open the dowser and winding # 2 to close it. When you press the changeover pedal at the incoming projector a current pulse is sent to winding #1 of the incoming machine and also to winding #2 of the outgoing machine. The incoming machine opens and outgoing machine closes.  |  IP: Logged Steve Scott Phenomenal Film Handler Posts: 1300 From: Minneapolis, MN Registered: Sep 2000 posted 12-22-2005 06:45 PM                     A dowser is anything that hides the light source. Many old-timers will refer to changeover devices, such as zippers or Kelmar units, as dowsers. In my vernacular, the only dowser is the hand dowser in the lamphouse.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 12-22-2005 06:54 PM                        When we move, overhaul or install a projector we always change the changeover to one made by Kelmar. There are internal "stops" within the changeover to eliminate this kind of slippage problem. The older (1940) designs are prone to burn out and misadjustment; the Kelmar is recent and is much less prone to trouble. (Strong makes a seemingly identical changeover; BUT internally certain adjustment are not made and certain clevis pins are not durable enough. Avoid.) Louis  |  IP: Logged Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 12-22-2005 07:25 PM                        Looks like I may need a new changeover altogether. I tightened the speed adjusting screw, followed by the locknut, and... snap. The locknut sheered in half! I don't know if I should replace the screw and locknut ($10.00 + shipping) or just get a Kelmar. What will a Kelmar set me back?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 12-22-2005 08:17 PM                     Get the Kelmar far less grief in the long run  |  IP: Logged Aaron Sisemore Flaming Ribs beat Reeses Peanut Butter Cups any day! Posts: 3061 From: Rockwall TX USA Registered: Sep 1999 posted 12-22-2005 09:01 PM                     quote: Andrew McCrea Just out of curiousity, what is a changeover? I always thought that it was the same thing as a douser... FWIW, changeover=electric dowser. One and the same. There is also the 'hand dowser' that is the lever that cuts the light at the lanphouse snood. -Aaron  |  IP: Logged

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