Technical Support Document 016 - 6/94

SENTINEL LENS ENCODER REPLACEMENT

The Sentinel Enlarger uses two optical encoder modules to determine its position for focusing. Replacement of one or both of these modules will change the reference of the machine and cause all existing lens setups to be out of focus.

CAUTION: Take care with the encoder module's steel measurement wire. Any kinks or other damage to it will affect the autofocus operation of the Sentinel after a module is installed. Do not let the wire snap into position at any time. This could break the wire or otherwise cause it to retract into the module, which will damage it.

REMOVAL OF THE OLD MODULE

1. Separate the negative and lens stages by about 10 inches.

2. Detach the bellows from the bottom, lifting the hook-and-loop carefully.
   
3. Turn the main power OFF.
   
4. Remove the bottom cover plate from the lens stage box. This is the compartment into which the bellows encoder connector cable enters through a rectangular hole just behind the encoder module itself.
   
5. Inside this compartment, there is a circuit board screwed to the top face. Locate where the encoder module plug is connected to this board. Remove this plug, noting it's orientation: It can plug in two ways, but the correct orientation is such that pin 1 on the connector (The end with the white spot) is nearest the small "1" printed on the circuit board.
   
6. If the cable is routed under this circuit board, it may be necessary to loosen the board mounting screws in order to get the cable out.
   
7. Locate the steel measurement wire where it exits from the top of the encoder module. Place the extra wire clamp, provided with the new module, on the wire where it exits the old module through the top of the lens stage. (See Fig. A)

8. By slowly and gently pushing the lens stage up towards the negative stage, release the tension on the encoder wire. The clamp installed in the last step should hold the wire in place at the exit hole, allowing the rest of the wire to become slack.
   
9. The end of the wire is attached to the lens stage by a slit block near the front, left corner of the bellows area. With the wire slackened as a result of the previous step, loosen the two small screws that hold this block in place. This will free the end of the wire.
   
10. Carefully pull the wire back through the three pulley assemblies through which it is routed. If the wire snags in a pulley assembly, push it back in the opposite direction to free it again. Twist the wire between your thumb and forefinger to help get it through any stubborn pulleys. Carefully note how the wire was routed through the three pulleys: you will have to duplicate this routing when installing the new module.
    
11. With the wire free, make a loop in it anywhere after the clamp. Place a piece of masking tape or duct tape through the loop and stick it to itself. This will act to keep the end of the wire from retracting into the encoder module.
    
12. Pull the end of the wire up from the exit hole to move the clamp, placed in step 6, away from the surface which it was resting on. Still holding the free end of the wire, remove the clamp.
    
13. Slowly let the wire retract into the encoder module, letting it stop at the taped loop. The loop will now be holding the wire from retracting all the way into the encoder module.
    
14. Remove the encoder module by loosening the three flat head screws holding it onto the lens stage. Two of the screws may be partially covered by the hook-and-loop fastener strip for the bellows. Push the strip aside or cut it with a razor to gain access to the screws.

The old encoder module should now be completely removed from the enlarger.

INSTALLATION OF THE NEW MODULE

The new encoder module is shipped with a wire clamp, like the extra one, installed on its measurement wire. There should be about 24" (2 feet) of wire extended out of the module. This free wire length is intended to make threading it through the pulleys easier.

1. Thread the free end of the wire up through the exit hole in the lens stage, where the old one was. Temporarily secure the module, through one of its mounting holes, with the extra-long screw supplied. If you do not have this screw available, use whatever means you have on hand (tape, etc.) to temporarily hold the module in the relative position shown. This will allow the module to hang under the lens stage, yet give room for the wire clamp to remain in place on the wire until the other end is attached. (See Fig. B)

2. Feed the electrical cable from the encoder module (the rainbow-striped ribbon) through the rectangular hole and into the interior of the lens stage box. Plug its connector into the junction circuit board where the old one was, with the brown wire closest to the small "1" printed on the circuit board. Route the cable as necessary to keep it from entangling with any moving parts inside the box. For now, leave the cover plate off the box.
   
3. Thread the free end of the steel measurement wire through the three pulleys. To do this, grasp the wire about 1 or 2 inches from the end. Insert the end into the pulley, in the center of the groove, and carefully push it through. (See Fig. C) The end should come out the other side of the pulley, at a right angle from the direction of insertion. Continue for all three pulleys. Please note the WARNING at the beginning of this instruction sheet. Route the wire through the pulleys the same way the old one was routed.

4. When completely threaded through all pulleys, the wire should move freely back and forth in its travel. The free end may now be attached. Bend a short section at the end of the wire (One quarter of an inch or so) at a right angle. Insert the wire into the end of the small slot in the wire attachment block, so that the bent portion at the end of the wire will be clamped under the block when the two screws are tightened. (See Fig. D) Tighten the screws when wire is properly positioned. When tight, tug on the wire to test that the end is securely held.
   
5. Unscrew the long temporary screw holding the encoder module in place. Grasping the module, gently pull it downward, keeping the wire exit pointed upward, to put tension on the entire wire length. Remove the clamp.
   
6. The encoder module may now be secured with the three flat-head screws. Position the module and install one of the screws, this will hold the unit in place until the remaining screws are installed.
   
7. Re-attach the bellows and re-install the lens stage cover plate. This completes the installation of the new module.

Now that the new encoder module is installed, the computer does not know where the machine is mechanically. This can cause some unexpected behavior from the Sentinel if you allow the machine to go into autofocus mode with the new encoder. Please observe the following steps to get the machine back on-line in a safe manner.

1. Turn the power on while holding the CANCEL key until "MANUAL" appears in the upper right corner of the keypad display.
   
2. Once the machine is up and running, it should be in manual-focus mode. Do Not put the machine into Autofocus mode. The lens setups which were done with the old encoder can cause erratic movements with the new encoder.
   
3. With the machine in manual-focus mode, go into the Sentinel Doagnostics menu and run the "Reference Enlarger" option. (Press MENU, <8>, ENTER, <7>, ENTER.) This will cause the machine to reference normally, but, since it is in manual-focus mode, we will avoid any erratic movements immediately after the referencing finishes.
   
4. At this point, you should immediately setup all lenses used with the machine before going into autofocus mode.

Also Check Easel and Carrier setups for soft focus/incorrect sizing and re-do as necessary.

For any questions or problems about this procedure or any other matters concerning ZBE products, please contact us at the phone, fax, address or e-mail below.