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Further adding to their life is the fact that Dolby has learned a lot more about the care and feeding of these rascals. Dolby is now testing all of them and they have had at least one batch with a 90% reject rate. They have found that most of the LEDs have an initial drop-off in output during the first 30 or so hours of use. Therefore, Dolby cooks them first to get past this period so that when you put them in service they will be stable. This also weeds out the potential trouble makers.

How long should they last?? We still don't really know because of all the factors just mentioned. We recently had a call from a technician asking this question because he was concerned that he had some that had lasted only two years. Further conversation revealed that in this theatre the LEDs had NEVER been turned off.

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First off. Before raising your LED level (via the power supply), I hope you maxed out your pre-amp gain (CP-55, if memory serves). As others have stated, the key is running the LED at the lowest level possible. We normally start the LED supply at the minimum setting.

One thing to check on your readers are the links on the reader preamp...one is located above the IC and one is located below (they are wire links)...yours may still be in place. If they are, cut them and you will get yet more gain.

Also, I have found that using the factory lens holder does not have optimal lens placement resulting in the need for increased amplification/LED intensity. That is, if you put in the ASR series of readers (Component Engineering systems designation) vs the STR or STRD series, your level out of the ASR system will be lower in level.

In any event, I would find it odd if your LEDs need changing. We have LEDs older than yours still working in analog. We are finding that digital leds are getting about 7500 hours and analog leds are getting 15,000 hours and more. There is some variation with some failing much sooner and some marathon ones that never seem to age past a certain point. Your theatre doesn't run that many hours as compared to a typical grind house so again, I find it odd that your LEDs are at the end of their life unless you have been boosting the LED level.

Back when you units were put in, we follow recommened practice of having them on all the time to avoid shocking the LED and to avoid the thumps and squeels on power up. However, with LEDs (particularly the digital ones) not going the distance we would like...we now switch the LED power supply (not the LED) with the motor. the CE LSR-30 supply will soft star the LED on power up. By having the power supply follow the motor, the thumps and other offensive noise will not be an issue since it will stabilize prior to changeover and will stay on until after changeover.

Steve

Steve, I don't understand why you can't have the same results with an original lens mount. We have folks doing it all the time. You are using the same light source and the same reader. The only thing different would be the in-and-out location of the lens holder, and you should be able to adjust the LED into position. If you can't get it in far enough without bumping into the sound drum, just shim up the lens holder about one thickness of film. Am I missing something else?

On the matter of the relative life of the digital vs the analog, this is changing. Dolby is now shipping a new digital camera circuit board, the Cat. No. 954R, which replaces the older Cat. No. 654R. This unit not only has more gain, but uses a new CCD which is twice as sensitive. When we add to this the faster lenses we are now using, we now ship the digital power supplies set for around 110 mA whereas we used to ship them at 450 mA (for 4 volts of video).

One further note on milking the most out of the LEDs, the light beam out of these things is quite narrow vertically. Therefore it is necessary to be sure that they are aligned optimally. Just a little up or down adjustment can make a big difference in how much light is getting into the reader which means how much current they need etc., etc., etc...........

Actually, the problem seems to be height not lateral position...that is, if the LED is pointing level and straight back and the reader is level and pointing forward, the two heights will not be the same (I think the lens will be slightly higher)...sure you can rotate the LED so it maximizes but it won't be as good as your lens mounts....this has been pretty consistant in my findings.

Steve

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"Old projectionists never die, they just changeover!"

To be honest, I haven't installed that many ASR systems...most of our customers are thinking digitally.

Steve