Star Tech Journal

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Stern Joystick PCB T
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I
ng Procedure
34567
Stern has introduced a new type of joy stick board, called a photo reflective unit. It
operates by the use of infra-red light that is transmitted from, and reflected back into
the lens by a polished washer. There are 4 photo reflectors (up, down, left, and right).
When trouble-shooting a reflector, there should be +5V between Pin 1, which is
designated by a white dot, and ground, (pin 1 on connector J-1 ). By covering the
reflector, the voltage should drop to 1 ½ to 2 volts if the reflector is good.
After determining that the photo reflector is good check the outputs of the LM339
(location U-1 on the PRU-1000 Bd.). Still using pin #1 for ground, check the following
pins on connector J-1 for individual outputs. Pin 7 for left, pin 4 for right, pin 3 for down
and pin 6 for up. Again +5 Volts should be measured. By covering the reflector for the
direction that is not working, the voltage should go to 0 volts. If it stays at +5 volts, the
LM339 is bad. If the volts drop to 0 and the player still won't move, check the
connector and the cable for bad connections.
+5\1
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