While I too deplore the practice of "bumping" the film down, most of those who do it do so with the manual motor switch whereas the LED supply can be switched by the automation's motor relay. I recognize that this isn't all neat and tidy (how do you turn the LEDs on for servicing?), but you can definitely improve the life of those rascals.

The other way to look at it is that if you take the cost of your entire sound system and derive the percentage for the cost of a replacement LED, it will probably turn out to be a most infinitesimal number. But, remembering that it is the source of all that sonic magnificance without which the rest of the system is meaningless, just replace the thing every couple of years....but watch it regularly.

 |  IP: Logged

Of course, we could use one of the unused switches on the rear of the automation apron for this, but it means one more switch for the new trainees to remember.

The biggest problem with inching the motor on and off with the motor switch is that motors draw much more current to get from a stopped position to a running position than it does to keep it running. This practice is particularly hard on the motor and the switch (not to mention the projector's gear train which gets to "slap" against both surfaces of every gear tooth).

 |  IP: Logged

The answer to your JJ question is in two parts. If one is thinking in terms of analog conversion only, there is no problem. You remove the original exciter lamp bracket, the slit lens and the photo cell bracket. The new lens/pre-amp assembly slips into the original slit lens mount and the new LED assembly fits right where the old cell bracket was. If you are doing the complete conversion including SRD, however, then things change. It has always been a basic concept that our readers can be installed without drilling or tapping any holes or otherwise cutting any metal. In order to avoid having to cut into the bulkhead isolating the exciter lamp housing, we had to drop the digital reader down farther and so were trying to read the digital track too close to where the film was leaving the sound drum. More wrap was needed around the drum. Well, as long as we are going to make this change lets go ahead a make a few more improvements to what has always been the weak part of the Century head. This meant that we had to sacrifice the 70mm bypass skid and roller. We felt the trade-off was worth it as Ballantyne was already cutting a hole in the front of the picture heads and bypassing the whole sound head, and while we didn't like it, this could easily be done in the field. Most people, however, have decided to just abandon 70mm. In any event, our new pieces sure improve on Century's original design. These pieces plus a good VKF sprocket and a change in bearing loading render this a really good sound head.