Film-Tech Forum ARCHIVE: manual change over setup question

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Posted by Bradley Johnson (Member # 5154) on 04-01-2009, 12:43 AM:

I am about to change the old readers in our Simplex SH1000s. This is a dual projector set up. The new readers will be RSTR-2000s. The current change over system is a AC wall switch that actuates the projectors changeover shutter (sorry I don't know the actual name of the part)and in addition trips a relay that switches DC power to the existing reader/exciter lamp set up... In other words, when one projector is selected via the wall switch, the power to the other reader and preamp is switched off. My question is should I duplicate this action with the new readers or should they both be powered during the film? The cinema processor is going to be a CP-65 and it was my plan to just trip a relay to switch between projector inputs on said unit. (as per the instructions for the CP-65) Keep in mind that the original sound system had no cinema processor at all, just the two readers feeding a mono amp. The only way to switch from reader to reader was by turning the power to them on and off........I guess my real question is,,,,is there any reason to turn the power on and off on the new led readers, and is this actual a harmful to them?

Thanks!!!!

Posted by Brad Miller (Member # 2) on 04-01-2009, 01:27 AM:

Leave the power on both readers during the show. If you don't, you won't be pleased with the changeovers. [Wink]

Posted by Louis Bornwasser (Member # 3063) on 04-01-2009, 06:01 AM:

Wire the readers to feed from the respective motor, so they are OFF when the motor is off (LOnger life for LEDs.)

Make changeover using the CP65 changeover circuit. (You can use a latch relay or use the existing switches (maintained contacts) to ground the changeover point on the CP.) Louis

Posted by Dave Macaulay (Member # 813) on 04-01-2009, 02:12 PM:

What kind of picture changeover do you have?
The usual American type uses a powerful solenoid that moves the changeover shutter up or down and it's powered by a momentary switch or pulsed relay. This coil is not made to be powered all the time, and will melt pretty quickly if you do that.
Ballantyne is different (whew, very different!) as are the European projectors and oddball studio stuff like Magnatech and such.
Anyway, you may have a momentary switch to operate the changeovers, with the wires crossed so opening one machine's changeover shutter closes the other. This usually means another switch for sound, or the picture changeovers might have a built-in switch for sound changeover - USA ones are a microswitch crudely grafted onto the changeover coil unit, European ones are hidden inside somewhere.
As far as I recall the CP65 needs a maintained contact closure to do a sound changeover. If you have a separate sound changeover switch you can use this for the CP65 changeover. If you have a double pole toggle switch that does both picture and sound changeover you can use it but you might run into a noise problem with the CP65, it doesn't like a lot of electrical noise on the changeover lines and sharing a switch and/or conduit with the picture changeover wires might not be good.
With momentary switch picture changeovers if you want to eliminate the separate sound changeover switch... you can use a picture changeover auxilliary switch (if you have them!) or a memory (latch/unlatch) relay. The relay cost about $100.00 the last time I got one but they last pretty much forever.
The LED reverse scan power issue is easiest if you do as Louis suggests - this saves the LED and the power-up "POP!" transient will happen at motor start and all will be ready at sound changeover.
This wiring approach alone doubles the "real" life of each LED compared to just powering both during show times, and most working cinemas also leave the systems powered several hours a day with no show running if you consider the time between powerup and the first show, time between shows, and time after the last show before powerdown. I've even seen them on 24/7...

Posted by Bradley Johnson (Member # 5154) on 04-02-2009, 11:32 AM:

quote: Dave Macaulay
The usual American type uses a powerful solenoid that moves the changeover shutter up or down and it's powered by a momentary switch or pulsed relay.

Yes this is our current changeover setup. However, instead of having some kind of switch for audio on the changeover solenoid there is a relay that is also connected to the momentary switch that is switching the DC voltage for the current readers.

quote: Dave Macaulay
The LED reverse scan power issue is easiest if you do as Louis suggests - this saves the LED and the power-up "POP!" transient will happen at motor start and all will be ready at sound changeover.

I am going to go this route and use the existing relay (without the DC current of course) to switch the CP. I like the idea of coming off the motor power as yes, the projectionist leaves the power on for extended periods.

Thank you for all the help,,,,
I will post with the results!

Posted by Jim Cassedy (Member # 4115) on 04-03-2009, 09:53 AM:

When upgrading a very old change-over theater with mono
amps and no processor of any kind to cyan-readers several
years ago I was faced with a similar problem.

I wound up keeping the "electroncs" portion of the
RSTR-2000's powered up at all times, but used a relay
that was previously was used to switch exiter lamp
current to switch the LED's on each reader on and off.

But this produced an annoying "pop" at the changevover.

Putting a 10,000uF cap across the LED and a 1.5k resistor
in series with the LED DC input solved the problem nicely
by preventing the inrush of current to the LED.

(and a big thanks to Sam Chavez, who gave me this tip
and saved me a whole lot of re-wiring!)

Posted by Bradley Johnson (Member # 5154) on 04-18-2009, 12:21 PM:

Ended up using 120 volts from the projector motor switches to power the new readers and the original relay that switched DC power to the old readers (DC power supply is now gone, just using the relay) to trigger the CP65 projector change over circuit. Works great, no pops. Wouldn't mind a little automation, or at least a remote for the CP-65. Manually dimming the house lights, opening and closing the curtain, turning off the advertising projector, and finally switching the processor from non sync to film is a bit of a tap dance,,,,fun to watch but hard to perform,,,,, [uhoh]