One of the screening rooms I work at is located in a building that dates back
to 1914. The elevator control system probably dates back to the early 1930's.
Big friggn'-huge motor generators, and thyratron control tubes, and more
relay racks than you'd find in an old telephone company switching office.
I recently took a friend down to the basement to see it and he was in awe.
Next time I'm there, I'll try & get some pictures!
Posted by Jeff Taylor (Member # 443) on 01-29-2015, 01:12 PM:
You should have seen the lighting control room in the basement level at RCMC. They claimed to be the largest volume purchaser of vacuum tubes in the world after NASA.
Posted by Stephan Shelley (Member # 8587) on 01-29-2015, 05:53 PM:
Those are Century MG sets at the Paramount Oakland. Two of them. One of the two is used for movie classics with Strong Excelite Carbon arc lamphouses.
Posted by Charles A. Petty (Member # 3458) on 01-29-2015, 08:04 PM:
There are two Roth Actodector motor-generators in the basement at the Oakland Paramount, not Century. See attached photo of the data plate. 
Posted by Stephan Shelley (Member # 8587) on 01-29-2015, 08:35 PM:
Check the motor side. Century 3 phase motor.
Posted by John Eickhof (Member # 323) on 01-29-2015, 09:05 PM:
Yes they are Century Electric Motors ( standard on Roth equipment ) However, CE was not affiliated with Century Projector corp. The entire motor-generator set was sold as Roth and the Actodector trademark. ( just like Transverter was the tradename for Hertner Electric ) Hobart, GE, Continental Electric, Martin, Robin Imperial, and Westinghouse also made DC arc lamp motor gennies, several used their own electric drive motors, others contracted out for their motors. Usually the two piece coupled types used various motor suppliers. The field controls, meter panels, ballast resistors, and accessories were generally made in house by the generator maker. IR international Resistor supplied most of the actual high current resistors though.
Posted by Charles A. Petty (Member # 3458) on 01-30-2015, 03:37 PM:
Speaking of high current resistors...
Posted by Stephan Shelley (Member # 8587) on 01-30-2015, 09:54 PM:
Anybody have a pic of a synchronous rotary converter used for arc power? Basically they are a mechanical rectifier. I know of some for railway power. I have heard that some theatres used them as well. A little more efficient than MG sets.
Posted by John Eickhof (Member # 323) on 02-01-2015, 11:57 AM:
The only synch converter I know of was the Ashcraft Cyclex system that used an electric motor driven AC converter that produced 96 cps 3 phase power fed to special static transformers (Ashcraft terms as control units) for each arc lamp that used a pair of 7mm ac carbons. The light pulsated at twice shutter interruption thus when in synch with the projector it produced a very smooth, intense flickerless light. The transformers changed they the arc, changes 3 phase to two phase so one phase feeds the arc in each lamp, and an adjustable air gap coil which in essence is a magnetic valve between the primary & secondary that allows the arc feed motor accurate control of the arc length. Basically if the gap is set correctly, the feed motor would automatically keep the arc at the correct gap. I have never operated these lamps but have talked with projectionists and technicians in the past who have and they said the original set up was tedious but once completed the arcs were very stable and needed no attention from the projectionist after they were struck.
Posted by Robert Koch (Member # 3728) on 02-03-2015, 03:15 PM:
John
I dont know who the old timers you talked to concerning the Cyclex;
but Im older than dirt,and I ran Cyclex for non other than Ray Syufy and his parents, Bill and Pauline at the Rita in Vallejo before I went overseas. My experience was different than your other old timers. You couldnt turn your back on the damn thing cause it was always blowing out.
Posted by John Eickhof (Member # 323) on 02-03-2015, 09:49 PM:
Hi Bob, What was usually failing? Or the weak points? I had never operated nor worked on one but Jim Gillespie in southern cal had operated the lamps and there were a few set ups in the LA area he said the biggest problem he remembered was adjusting the variable speed pulley on the drive motor to match the actual shutter speed of the projector mechanisms. (they had to average it because there were differences in sped of both projectors typically) It definitely was an interesting principal! By the way, do you have a wiring diagram for a hertner M40-80 1kw motor generator in your RCA service bulletins?
Posted by Robert Koch (Member # 3728) on 02-04-2015, 02:31 PM:
Sorry John; all of my RCA stuff is gone including my ERPI BIBLE, which I should have held onto and profited from, but foolishly didnt.
Posted by Stephan Shelley (Member # 8587) on 02-04-2015, 04:01 PM:
I think you are talking about a different type of converter than I was referring to. I am talking about a rotary converter. Has multiple phase slip-rings on one side of the armature and a a commutator on the other. One end of the windings on the armature is on the one of the slip rings and the other on a commutator bar. The armature spins in sync with the AC frequency so that when the AC peak hits the commutator bar is under the positive brush and when the negative dip hits it is under the negative brush. You rectify existing AC current. I know of some railway 600 V DC machines in working condition and are used at time in operating museums.
Posted by John Eickhof (Member # 323) on 02-04-2015, 07:37 PM:
Thanks Bob, As for the converter, I can't say I've ever seen anything like it in a theatre setting. Interesting idea, so by multiplying the phases it puts out direct current? I wonder how smooth the DC is? Amount of ripple, etc?
Posted by Stephan Shelley (Member # 8587) on 02-04-2015, 08:02 PM:
The railway one has 2400 volts 3 phase going into a transformer that has combination delta and star connections to give phase shifts and puts out 6 phase 440 v AC. The rotary has six sliprings and multiple poles so there are more than two sets of dc brushes. At least 6 sets. This unit was built as a portable booster unit. It would detect the drop in voltage cycle itself on and turn itself off later. 1920s relay tech. GE made it for the Sacrament Norther RR.
I have heard of smaller units for theatres. I heard one problem was if it is left to start on its own you never knew the polarity it would come up as. The railway automated one starts as a repulsion motor at half voltage. As part of the start-up it pluses the field so that it locks in the same polarity when it locks in as a sync motor. I have heard projection booths that used them had polarity reversing switches.
They should be as smooth DC as a generator. Generators are really stationary field alternators. It is the Commutator that makes it DC. The ripple has a lot to do with the number of field poles and brush sets. Same with the rotary converter and also in the case of the rotary converter the number of phases going in.
Posted by System Notices (Member # 2357) on 05-07-2016, 12:34 AM:
It has been 457 days since the last post.
Posted by Steve Kraus (Member # 476) on 05-07-2016, 12:34 AM:
Bringing up this thread to ask if, before silicon rectifiers, were arc lamp supplies always M-G sets (AC motor spinning DC generator) or were they ever rotary converters like Stephan Shelley was discussing.
Like this:
https://en.wikipedia.org/wiki/Rotary_converter
I'll summarize in case the link ever fails that it was like a motor and generator merged into one but some of the energy can go directly (via brushes, slip rings, and commutator) while some moves mechanically (compared to an M-G where all the power goes through mechanically). They were common for electric railways.
I'm wondering if maybe the power output wasn't smooth enough for projection arc use where non smooth power would cause flicker as it interacted with the shutter. Or maybe they were only practical in very large sizes and for lamps an M-G was more cost effective.
Posted by Jim Cassedy (Member # 4115) on 05-07-2016, 01:32 AM:
![[Smile]](smile.gif)
