Great idea. How in the world do you do that?

My first theatre had the new Strong switchers. I loved the potentiometer for adjusting current, rather than messing with the taps. I also loved being able to change out the whole thing, rather that having to change diodes or something else if the rectifier goes bad. And I love the trouble lights!!! However, within a year, we had three go bad. I have heard similar reports from other theatres. (Someone told me he had 3 go bad in one week!) So I guess there's a little give-and-take either way you go.

As far as trying to trouble-shoot one, you're not supposed to! They are not user serviceable. I suppose that's why they're so easy to change out. Just pop in your spare and send the old one back to Strong.

I don't know of any major problems with the high reactance rectifiers.

 

I still think that my as-yet-unbuilt outdoor will have two-projectors
with hour-long reels at the ready, that way if one were to go down, at least you could keep the screen lit with minor inconvenience of a
thread-up mid-show. What would you do?
 

Shut down the fans in one and you'll change your mind! They actually get quite hot with out a fan and will shut down. In the switchers its the fan that keeps em cool. Older Strong switchers were notorious for overheating when you used them in a booth that was hot say in the summer. I've been to booths that hvae the tops removed and have a 3 foot window fan blowing on them!

In any rectifier that has diodes, the diodes are only rated for so mnay thermal cycles before they will mechanicaly fail. I have seen alot of this in older Christie rectifiers and some Irems but mainly those rectifiers that have no cooling fan. Also diodes that use that green epoxy type seal are prone to literally fall apart after a number of years. Using diodes that are glass sealed will allow much longer life and more thermal cycles. Even if a rectifier is fan cooled the diodes still go through this thermal cycling at the silicon chip. There is some thermal resistance in the diode itself so the actual silicon chip itself runs a bit hotter than the diode casing, and there is another thermal joint adding resistance between the case and heatsink. Lotys of heatsinking and or fans are the only way to reduce this failure but you will never see a rectifier that never ever fails at some time in its useful life.
Mark @ GTS

The newer Strong consoles we have been receiving in the last couple of years or so, however, have been equipped with intake fans on the non-operating side of the door. These fans seem to help greatly on cutting back on the number of failures.

In problematic booths, (those that have had 2 or more failures)(usually 7K), I have added fans to these older consoles and, touch wood (knocking on head), have not had a failure in over two years on these units.

I would like to know, for those of you who have experienced failures with switching rectifiers, did they fail at the start of a show or during a performance?

Eventually just about any peice of equipment will fail. I expect rectifiers to be no exception. But the problem, at least in my experience, is how quickly they fail. 3 in a year?? Seems rather unreasonable, if you ask me. Then again, I've heard of theatres that have had no problems.
 

Still, I have had some luck (and learned a lot) with repairing them (not without some help on finding information from some of the people here on Film-Tech). I agree with an earlier statement Paul made, in another post, about it being easier to send them back to the factory for repair.

However, with the hassles of getting them through customs (CAN. - U.S), plus the time incurred being without a spare rectifier, and no, we don't yet have 7K reactance types on hand, not to mention the logistics of getting a heavier than sin reactance type up to the booth on a Saturday afternoon to save a show for the weekend, I have no choice.

If you blow a power supply or a lamp, just simply grab your spare power supply and lamp, drag it over to the station, throw the lamphouse on the pedistal, plug it in, light-'er up, and you are back on the screen!

Consoles, well, you are basically screwed if it was a switcher or any power supply and/or lamp failure.

Funny thing is, when Regal bought our theater, they acted like I committed an unforgivable sin by having a spare lamphouse and power supply sitting on a dolly "ready to go". They threw it away! What idiots!

Word also got to me that shortly after they bought our theater, (and I was no longer part of their HS operation,) two day's worth of shows were lost because of an exciter lamp failure. Yes - a stupid exciter lamp burned out! I was told nobody was allowed to change it.

The Regal techs do not like people messing with what they don't know. Did you have actual exciter bulbs, or LED's? If the were bulbs, that seems a little ridiculous, but if they were LED's I can understand. My last tech didn't even want the operators changing diodes for fear they might screw something up. I suppose I can understand his reasoning.
 

Why the spare lamphouse? Simple. It was already interfaced with the power supply. This eliminated the need for anyone to remove covers to connect or disconnect any wires whatsoever. Just plug it in and throw the switch!!

Customers are not to interested in waiting while the projectionist fiddles around 20 minutes or more trying to find out why the lamp doesn't light.

But they will probably wait five minutes for you to throw a lamphouse on the pedistal and throw the switch.

Each projection station was equipped with a 50 amp twist lock receptical for that purpose.
 

One interesting problem we have had ONLY with the newer plug-and-pray types (3 instances), is where the rectifier suddenly shoots up to full output. You get to the theatre to find out why a rectifier has been cutting out (thermal) and note that the current to your 4000-watt bulb is 200+ amps! (The potentiometer is NOT the problem, btw).

Looking forward to investigating this phenomenon further when I get the time.

With so many switcher-rectifier equipped theatres to service, it would be rather expensive to have a unit in each theatre. Better. we find, to keep them in a central location and deliver them as needed. (Yet another reason why technicians always have one arm longer than the other).

>>> Phil

That said...I think there are two ways of looking at the situation for permanent theatrical use...

First there is no real weight advantage to the switcher since the goal is not to replace it but for it to work. A conventional rectifier is almost always serviceable with minimal time (I say almost since sometimes it is the transformer and most of us don't carry that nor the large filter capacitor though I get the capacitor quickly in a pinch). Certainly, all rectifiers will fail someday...how well your system keeps the ignition noise, power spikes and such away from the diodes will play a big factor on if the diode fails at show start...how well it is cooled will play a factor on how well they last thoughout the day. I'm sure most of the old timers know of rectifiers they have NEVER had to go into yet others that seem like constant repeat customers despite being basically identical designs.

The second way to look at things is that using switchers, even with their failures, brings the repair down to the theatre level. That is, have your switchers on plugs and have a spare at each location...at that point, the theatre can simply plug in the spare, send out the defective one and when it comes back...the spare is at the ready. Based on the size of the complex, one should have more than one spare...in fact with the larger plexes 4 spares would not be unreasonable...heck most plexes carry more $$$ in spare xenon lamps. Since no spare xenon nor rectifier means the show won't run both should be on hand.

We have one customer that uses conventional rectifiers but has them on plugs as well so when even a diode fails the rectifier can be switched out with virtually no down time. With conventional rectifiers only one per booth is all that is needed (doubtfull more than one will fail and they are servicable at the theatre).

My personal vote is to use high-reactance rectifiers whenever possible in permanent installations. Their failure rate is less, meaning less customer dissatisfaction and are repairable on site for quick repair. Switchers can also suffer from semiconductor obsolecense whereas diodes and capacitors can be sourced from several manufacturers for the forseeable future.

If you are a rental house...that is a different story...swichers win pretty easily...they are light weight and set up quickly...Strong has theirs done quite nicely with MS plugs and any reputable rental house will have spare switchers at the ready on site (most have a 1:1 ratio of spares to show units).

Steve

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"Old projectionists never die, they just changeover!"
 

I know that there are hard-wired swithcers. Out of curiosity, do other manufacturers make switchers that are as easy to replace as Strong's?
 

Does the AC ripple in the xenon light output show up on the screen as flicker, or some sort of banding pattern? I assume the higher frequency of the ripple in the switching power supply doesn't "beat" with the refresh rate of the digital image?

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion