It'll be a Kelmar C/O box on top of a Simplex XL (PR-1003) Operated by the Comp. Eng. TA-10 automation.
I have virtually no concern about the mechanical hookup. It's the electrical that I have a question on:

Which set of terminals do I tap into in order to bring the power over to the relay? There is the 120v line for the automation power and another one for the projector motor power.

I was thinking that if I hooked it to the automation power feed the inductance from the solenoid coils would cause voltage drops/spikes that might cause the automation to crap-out.

Someone said that instead of 120vac, I should try DC solenoids. Makes sense. Then he said that I should just use the old exciter power supply to power them with 12vdc @10-15amps. That makes NO sense. Could a coil designed to pull in at 120vac work equally as well on 12vdc? I am assuming there must be some change-over units that are made specifically for DC voltage. Or, could I just put a bridge rectifier on the coils and feed them 120vDC?

What type of projectors do you have? I've seen a bunch of Century JJs that do not have ALL of their shields. The most important being the "tongue shield" below the head, then there is the one that is around the head and lastly, there is the one mounted with the changeover to stop it's EM at the source. I believe the Mu-Metal shield for the changeover for the JJ was called the SM-1556. Strong still lists it for $46.00 list.

If you wish to go the DC coil route...Essaney did offer DC coils Wolk, the current manufacturer of Essaney c/os may still offer them. Essaney used 120V changeovers.

The quality of the DC doesn't have to be high for them to work. You can simply rectify the AC line and filter it...however, your voltage will be substantially higher than 120 volts (closer to 170 no-load). By using some high power resistors, you can taylor the force of the changeover and not over drive it.

For the Kelmar style of changeover, you can merely replace the coils with DC units and obtain a suitable off-the-shelf supply for them based on what voltage you chose.

Remember that dealing with DC is not the same as AC. Relays and switches often have a MUCH lower DC rating and the contacts will pit and arc more. Make sure you use components rated for the kind of voltage/current you are using in DC. Even better protect the contacts with diodes.

Steve

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I have a quick comment on using DC. One good way to do this is by charging up large capacitors through some resistance and then when you call for the changeover the coils get a major pulse which makes them operate rapidly but because of the resistor there is not much sustanined current through the coils and therefore they are protected. I've never tried it, but I don't see why some young Tom Edison can't work out a way to do this using the existing AC coils.

Calling Josh Jones!!!

Are we talking about those things that look like an oversized mylar capacitor but really contain a cap and a resistor... Making it, in reality, a "Resist-O-Pacitor"?

I'm going to need two of these, right? Hook them in parallel with the coil?

What's a good source and a ballpark price?

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And Bernie, I will take you up on that for sure! I can't get back to the Loews Jersey soon enough. BTW, anyone who is anywhere near Jersey City NJ and hasn't stopped in to see the work Bernie and Bob are doing on this magnificent theatre and the AWESOME booth, are missing a real treat.

And Gordon, now you've got to explain to me what a snubbing diode is -- how do I get one and how do I get it to go into snub mode?

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