Film-Tech Forum ARCHIVE: Reverse Scan on Automation

This is topic Reverse Scan on Automation in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005355

Posted by Paul G. Thompson (Member # 655) on 09-21-2003, 02:43 AM:

Seems as though two of our houses were converted to CE Engineering reverse scans do not like our automation interface. Orginally, the non-sync constant closure required by the older Ultra-Stereos was released on motor start. The exciter lamp was brought up on Change-over open.

To do a little re-configuration, probably the easiest way to do this is to put the power supply on exciter on relay in the automation. I am very reluctant to do that in the feed to the reverse scan because the output of that thing is regulated.

I feel more comfortable doing the switching on the primary power to the reverse scan power supply.

However, I am not sure how well those power supplies will handle the "hammering" it will be subjected to in this enviroment. Most electronic equipment does not like to be switched off and on excessively.

What has been your experience in this area, and what would you do? Will the power supplies be able to handle switching on and off 4 times a day without going BLOOY in about 6 months or so?

I don't know - and I don't want to really take a chance until I hear form some of you pros who were confronted with this problem.

Thanks in advance.

Posted by John Westlund (Member # 913) on 09-21-2003, 03:36 AM:

I am also curious about how to interface the power supply to the automation. We are installing a CE reverse scan on Friday. We have our exciter hooked up to the Utility relay in our TA10 at the moment.

Posted by Paul G. Thompson (Member # 655) on 09-21-2003, 03:55 AM:

John, it is fairly straight forward. If you have a processer that will accept a pluse instead of a constant closure for non-sync, I don't think you will have any problem.

However, if you have a processer that needs a constant closure to lock it in non-sync (or whatever) I would think your best bet is probably the same thing I will probably do. Use a latch relay pulsed by the COO and COC relays in the TA-10.

Posted by Jean-Michel Grin (Member # 1360) on 09-21-2003, 04:25 AM:

Hello Paul,

In our houses, we converted past year four Simplexes heads for CE reverse scan.

The primary side of the power supply has to be controled by exciter relay (In a Strong CPA-10 Automation). Component Engineering don't recommend to switch the Led's power line, because the CE power supply ensure a "slow start" current rating to the Led.

I believe that the input of the power supply is protected by a varistor too, but I'm not sure.

The first thing that coul be blow up after six month could be the relay in Your automation if is under sized to handle the primary current of Your CE power supply (the current at the primary side is less than 2 amperes)

I like the idea to put a "bi-stable" or "toogle" relay on the change-over. But i will to add an three-position switch labeled ON-OFF-AUTOMATIC, to allow to switch the exciter manually. This can be verry usefull somedays...

Bye, and apologyses for my weak English [Smile]

Posted by Scott Norwood (Member # 30) on 09-21-2003, 10:13 AM:

I'm confused. Why does the LED need to be switched on and off at all? With a modern Dolby processor, the exciter/LED should be able to stay on at all times during the day. The only time I've seen switched exciter lamps is with older changeover setups where both projector inputs were active at all times. Since Dolby processors (and, I assume, others) have electronic switching for changeover and format selection, there's no reason not to leave the exciter/LED on all day. Or am I missing something? [Confused]

Posted by Richard Fowler (Member # 893) on 09-21-2003, 11:07 AM:

Leaving it on all day = cost and maintinance. Odessey products has a circuit board available to turn on and off the analog LED from commands from CP500 and 650 units. The older style CE power supplies are built like tanks and the low cost ASR type has soft ramp switching so this should not be a concern about powering up or down.

Posted by Jack Ondracek (Member # 1466) on 09-21-2003, 11:12 AM:

quote:
Since Dolby processors (and, I assume, others) have electronic switching for changeover and format selection, there's no reason not to leave the exciter/LED on all day. Or am I missing something?

Sounds like if he uses the same logic, the processor will switch from music to film audio when the motor starts. If the LED is on, everyone hears the leader.

Paul, I had that problem in Port Townsend when we automated that place. The theatre uses a Co-Operator, so an abundance of programmable outputs wan not available.

Vern talked this over with CE, and said the power supply is current-limited enough that switching the LED wouldn't be a problem. What IS a problem is that the LED is so fast it puts quite a click in the audio when it's switched. I put a little resistance & a small cap in the line to smooth that out & it's worked fine... about 6 years or so now. This would allow you to use an extra contact from your slide relay (if you're using one) to switch the Ultra Stereo over, and you can use the dry contacts from the exciter switch to run the LED.

Posted by Paul G. Thompson (Member # 655) on 09-21-2003, 01:27 PM:

Scott, you didn't misss anything. It is just some of the older equipment has maintained contacts for format switching and the newer ones have pulsed inputs to switch the format.

The problem is that some of the older automation units don't have enough contacts to set aside for special applications. The ones that did - well, those have been hogged up by other functions.

Jean-Michel, I agree. It is possible for the system to jump sync. A simple toggle to disconnect the switching logic would be the answer. In this manner the processer can be manually operated by the format card.

I set up an old Ultra-Stereo sometime ago. The format selecting was done with toggle switches. The Maxi-8 automation I was using didn't have enough "Holes" to put the processor on automation without adding some more relays. All switches on the format card were dis-engaged and the toggles were active. This system ran perfectly for 18 years until the theatre was closed.

Posted by Ken McFall (Member # 845) on 09-21-2003, 02:51 PM:

Paul,

I set up my readers on the projectors shutter open relay, I could have used the Show Run relay in the TA10, as using the motor relay had the led's going on and off more often as you laced up and ran down leaders etc. Using the Shutter open / Show run configurationreduced running hours of the led's considerably. I switched the primary side with no problems in three years or so. The pre amp cards were powered at all times to eliminate the slight 'thump' when the power switched on. We used Cinemeccanica basement readers.

Scott,

the reason for turning off the led's when not in use is to extend their life. In the early days stories were going round about their short life span, that and the fact that changing them normally requires an engineer it made sense to treat them gently. From my experience most engineers now set the signal gain high on the actual scan cards to allow the led current to be run as low as possible, extending the led's life considerably.

Posted by Gordon McLeod (Member # 33) on 09-21-2003, 04:08 PM:

I wire the Reader supply in parrallell with the projector motor and then I usually wire the output to the proj. 2 input of the processor and have the automation do a changeover and that usually prevents most of the rixk of pops and bumps
You could wire the changeover and the maintained format to the same relay with a set of diodes

Posted by Jean-Michel Grin (Member # 1360) on 09-22-2003, 12:35 PM:

I'm agree with gordon to wire the exciter supply in parrallell with the motor start; I've read that is better to ensure a "pre-reading" of the SRD soundtrack.
But in some case this is a bad idea. Why ?
In one of ours theaters, I equiped two Simplex projectors with a A/D combined reverse scan and red Led. The common power supply for the both readers was powered in parrallell with the motor start. And here began the troubles. At the least cue foil, at the end of the end credits, the automation (A Strong CPA-10 in this case) dosen't switch immediately the sound in non-sync, and then the noise of the tail was heard in the auditorium speakers [Big Grin]

For that I re-routed the wires of the exciter power supply trought the originals exciters control relay. It take a little delay to the SRD to decode the signal, but it stay acceptable [thumbsup]

Bye,

Posted by Paul G. Thompson (Member # 655) on 09-22-2003, 01:52 PM:

I have standard reverse scan analog readers. No digital in those houses. Along with that, the processors are old Ultra-Stereos that require a constant closure.

The option I have is to use a latching relay from the change-over open/close circuit to either switch the LED power supply like some of you have done or switch the Ultra Stereo format.

Posted by Jim Alexander (Member # 226) on 09-22-2003, 02:42 PM:

Although we don't have automation, we do have a CE reverse scan reader. As Gordon stated, wiring it to the motor start works quite well for us. The only difference is the power to the LED/Reader power supply is there on main power to the booth. On the power supply is two lugs used to provide soft power on to the LED and reader. When shorted, the power supply if "Off", when open it is "On". By integrating a relay to the motor start switch that energises and open these contacts, our reader and LED come on when they are needed.

Although this is not an automation system, I'm sure the same principle applies to the automation system. If your system has constant contact, no problem, if momentaty contact, then a simple latch relay, inline, would solve this.

Just a thought

[ 09-22-2003, 04:35 PM: Message edited by: Jim Alexander ]

Posted by Paul G. Thompson (Member # 655) on 09-22-2003, 09:51 PM:

Gentlemen, maybe I did a poor job in explaining this.

Once again:

1. The LED power supply is on at all times.
2. The Ultra Stereo gets a "holding closure" for non-sync via a relay that is on the motor circuit.
3. When the motor is started, the non-sync "holding closure" is immediately deactivated and the Ultra Stereo switches into the stereo format.
4. As the motor ramps up, all the crap the scanner sees is going out into the auditorium speakers.
5. When the movie is over, the change-over closes but all the tail-out crap still goes into the auditoruim.
6. When the motor finally shuts down, THEN the Ultra Stereo will go into the non-sync mode because the motor relay will send a closure to the Ultra Stereo.

This is not cool to allow it to continue. It is very hard on speakers, drivers, amplifiers, and the ears of the customers sitting in the auditorium and it makes us look like shit.

When the incandescent exciter lamp was being used before the conversion, the exciter lamp was switched on by the exciter relay at the same time the change-over relay opens the change-over douser. At the end of the movie, the exciter lamp was extinguished by teh exciter relay contacts at the same time the change-over douser closed.

What I was asking is whether or not the LED power supply would remain happy with 4 cycles per day over a period of time. By the answers some have posted, it sounds like it would stay happy as long as I didn't put a switching relay in the output side of the power supply.

If the power supply protested that, I would have made another approach....by using latching relays for the non-sync and stereo formats in this old processer in such a manner as to where the sound window would remain closed from the time the motor starts to the time the change-over douser opens and conversely, closing the sound window from the time the change-over douser closes and the motor shuts down on tail-out.

In short, I only want the sound window open when ther is a picture on the screen. Not before and not after. [Smile]

By reading your replies, I am convinced I did a shitty job of explaining what I wanted to do and how. [Smile]

Sorry for the confusion I caused.