Rob F.

<p>We shouldn't call the Elmar a Tessar. There is enough difference between them that it is better not to blur the distinction. Rather than thinking of the Elmar as being in the Tessar "family," I think it is better to say that they are both triplets--derived from the Cooke Triplet; the latter having been designed in 1893 by Dennis Taylor (who worked for Cooke). Both have four elements in three groups, the third (rear) group being a cemented doublet--two glasses cemented together to act as a single lens. The term triplet ensues from the three-group construction.</p> <p>Here's one of the differences: The Tessar's diaphragm is located between the second and third groups. The Elmar's diaphragm is right behind the first (front) element. According to one school of thought, this change was a stroke of inventive genius on the part of Max Berek, the Elmar's designer. Then again, it has also been said that that this was done to avoid infringement of the Tessar patent secured in 1902 by its designer, Paul Rudolph, of the Carl Zeiss plant. Take your pick, I don't know.</p> <p>Praise for the triplet design continues to pop up from time to time. There's been high praise for the 45mm f/2.8 Nikkor-P, and for the earlier GN Nikkor, both said to be derived from the Tessar. Whether they were or not, I don't know; but they do get special recognition for being in the venerable triplet family. </p>

I projectod about 20 slides in the usual way, when the projector died. The lamp faded to black, and none of the controls work. The fan runs normally. The manual states that this means that the electronic control system has shut down. Pressing the circuit breaker reset doesn't help. Letting time go by and pressing it again doesn't help. Removing the lamp carrier, both bulbs measure 0.2 ohms on a Simpson 260-XL. I assume that is an acceptable cold resistance for a 24 volt system, and that the lamps are not the problem. Running the projector with the lamp carrier removed doesn't cure the problem. As a former electronics technician/field engineer, I might be able to do some good, if I could get the projector apart. This means getting the top off. It would come off with four screws, except that the carousel tray won't come off until it has been unlocked. The tray blocks the top from coming off. I can't turn the lock/unlock control to the unlocked position to get the magazine off, because it has to be released first with the "Edit" button. But that is one of the controls that went dead when the electronics cut out. The magazine prevents removing the top. I've peered in from every removable panel, from underneath, behind, from the side, even through the lens opening. There must be a mechanical solenoid that can be released manually to allow the locking control to be rotated. But where is it? And after someone tells me how to get the carousel tray off, what do I do then? Will I find an internal fuse that might have blown? Is there a troubleshooting guide or schematic diagram for it?