Kodak Ektapro Slide Projector 4020 - Manual (Page 44)

Tray Motion
The STEPPER MOTOR is responsible for the slide tray movement. To move the tray one slide forward or reverse
47 steps are necessary in case a tray for 80 slides is used and 27 steps in case a tray for 140 slides is used.
The tray movement is controlled by the TRAY MOTION CONTROL PCB. This PCB contains two optical sensors,
one for the code wheel and one for the Zero Position Gear.
This PCB is sending following feedback signals to the MICROCONTROLLER:
- Tray motion direction (forward or reverse)
- One pulse for each step of the STEPPER MOTOR
- Tray zero-position signal in case the tray is in the zero position
If the STEPPER MOTOR moves one step, a pulse will be send back from the TRY MOTION PCB to the
MICROCONTROLLER after the step is done
.
If these pulses are missing, the MICROCONTROLLER assumes that the tray is not able move. The transport
stops immediately. A failure code is written into memory, the projector do not operate, the power LED is blinking
The projector must be deenergized. The jam must be cleared. As soon as the problem is solved, the projector
should operate after switching on again.
The DIRECTION + STEP SENSOR is a special optical device which generates two independent output signals:
- step pulses (count signal for the MICROCONTROLLER to calculate the tray position)
- direction signal (low signal for forward steps and high signal for reverse steps)
Tray Control PCB
Direction
+ Step
Sensor
Zero-Pos.
Sensor
Tray Zero
Direction
Tray Step
Slide
Tray
figure 3-6
Service Manual SM 2547-1
03/98 3-8 Kodak AG, Stuttgart