Technical Support Document 024 - 1/97

TEST ENCODERS DIAGNOSTIC FOR AUTOFOCUS SYSTEM

INTRODUCTION

The autofocus system in the Sentinel enlarger and Satellite Universal Scanner utilizes two optical encoder modules for determining the exact positions of the lens and neg stages. One encoder, located to the right of the lens mounting area, reads the distance between the negative or scanning plane, and the lens. The other encoder, located within the neg stage, reads the position of that stage relative to the baseboard.

The encoder modules measure these distances to within 1/1000 inch. Each module utilizes a thin steel cable to make it's measurements. These cables are visible within the bellows, and running along the right side of the front of the column above the neg stage.

Testing the encoder modules entails a diagnostic routine where each cable is pulled by hand from its module, the verifying that the numeric readout from each module changes appropriately. The procedure follows:

PROCEDURE

1. Move the lens and negative stages all the way to the bottom of the column, either using the jog arrow keys on the keypad, or by gently pushing them with the power off.
2. Separate the bellows by about 12 inches, to gain easy access to the space between.
3. At the keypad go into the TEST ENCODERS diagnostic that is found in the SENTINEL (or SATELLIITE) DIAGNOSTICS menu.
4. Lift the bellows from the bottom, separating the velcro. The top of the lens turret will now be visible, as well as a thin stainless steel cable the runs from a hole to the right of the lens turret area, up into the bottom of the neg stage, then back down near the front, right-hand corner of the lens turret area.
   

5. The screen will show something like what is shown below. (Please note that the numbers shown below are only examples; yours will most likely be different. This is normal.)
   
   

6. Grasp the steel cable under the bellows, where it comes down at the left front corner of the lens turret area. Be extremely careful not to bend or kink the cable in any way. Pull down, drawing the cable slowly downward.
7. While you do this, the top number on the display ("LENS POS") should decrease. If it does not, please contact ZBE for further information on replacing the lens encoder module.
8. After satisfied that the number decreased, slowly move the cable back to it's original position. Do not let the cable "snap" back into position. This may destroy the encoder module.
9. Verify that the number goes back to it's original value, plus or minus 2 counts. If it does not, the encoder may have trouble reading in one direction.
10. If this encoder performs as indicated, test the column encoder in a similar manner. First, grasp its cable and pull upwards while viewing the keypad. This cable can be found running along the right-hand rail mounted to the front of the column.
11. Pull the cable only a few inches at most. As you pull the cable upwards, both numbers on the display should decrease.
12. Once you verify that the numbers do decrease, slowly move the cable back to it's original position. The numbers should return to their original readings, plus or minus 2 counts.
13. If this is correct, the encoders are operating properly. Press CANCEL on the keypad to return to normal operation.