Technical Support Document 017 - 5/97

SENTINEL LENS TURRET LENS DETECTOR SWITCH CHECK AND ADJUSTMENT

When you turn the lens turret on the Sentinel Enlarger, that change is detected by two small switches located underneath the lens turret light-trap cover, at the rear edge of the round lens turret. The diagram below shows the area related to the switches:

When the turret it turned to any of the three lenses, the notch that goes with that lens will trigger either one or both of these switches. The combination of switches triggered (the top only, the bottom only, or both) tells the computer which lens is being used. If the signals from these switches are not reaching the computer properly, the computer will not know when the lens is being changed. Thus, when you program a lens, then move the turret to another lens, the computer will think you are still on the first lens. This means that, when you think you are programming the new lens, the information is actually being written over that of the first lens.

The easiest way to test if these switches are functioning properly, is to simply move the turret from lens to lens. With the computer at the main operating screen (where color filtration and size are displayed), there should be a small double beep from the keypad, telling you that the computer has registered that you have changed the lens. This double-beep will occur within one second after the new lens is moved into place. If it does not, then there is a problem with the switch signals getting into the computer. There are a couple of reasons that could cause this, as follows:

The switch levers are not engaging properly into the notches in the lens turret. When the turret is moved to a new lens, it will lock into place. In this position, the switch levers should be resting in one of the three notches cut into the edge of the turret disk. Depending on which position the turret is in, either the top, the bottom, or both levers will be in the notch. If the levers are not in the center of the notch, they may still be pressed against the disk body, and not be fully activated.

To make full sure that the levers are engaged in the notches, move the lever using a small, pointed object (a pencil will do nicely). Press the lever towards the switch body and listen for a very small "click" as the switch activates. When in the notches, the switch levers are actually "off." This is what is sensed by the computer. Moving the levers with a pencil will determine if the levers can be pushed "on" while in the notches. If pushing the lever does not make a click sound, then the lever is already "on," which means that the notch is not being sensed properly by the computer. If this is the case, the levers can be carefully bent as shown below:

This engagement problem with the switch levers in the notches can be created when the turret disk is removed to install a lens. All three notches should be checked.

A fault in the wiring to the switches could also cause such a problem. This, however, is highly unlikely, since this wiring is all internal to the machine, and therefore not subject to becoming disconnected or broken easily. It is worth checking this wiring only if the above suggestion (checking the levers) does not reveal the problem.