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Global Specialties
Checking out the PB-503A
Next, move the connections from PB1-1 to PB1-2, the NO point. Now the red LED should be lit
when PB1 is not pressed, and the green LED should be lit when PB1 is pressed. Repeat these
steps to test PB2.
The logic switches can be tested by connecting the output of logic switches 1 through 8 to the
input of logic indicators 1 through 8. Switch the logic 5V/+V high level switch to +5,
and switch the logic ind5/+V operating voltage switch to +5. Select the CMOS position
on the logic indicator TTL/CMOS threshold select switch. Now the logic indicators should
reflect the conditions of the logic switches, that is, red LEDs will indicate switches in the high
(logic “1”) position and green LEDs will indicate switches in the low (logic “0”) position. Move
each switch between its high and low position to verify proper functioning. Switch the logic
5/+V high level switch to +V and the logic ind5/+V operating voltage switch to
+V; the relationship between the switch positions and the logic indicator display should remain
the same, regardless of the setting of the 1.3 - 15 volts +V supply.
By using an ohmmeter, you can check the potentiometers. To do so, select an appropriate
range for measuring 10 kΩ and connect the ohmmeter leads to R1-1 and R1-2. With R1
rotated fully counterclockwise a reading of 0 Ω ohms should be observed. As the potentiometer
is rotated clockwise, the resistance reading will be seen to increase linearly up to 10 kΩ ± 20%.
Now move the ohmmeter lead from R1-1 to R1-3; with R1 fully clockwise the ohmmeter will
read zero ohms, and the resistance will increase linearly to the full value noted previously as
the potentiometer is rotated counterclockwise. Select an ohmmeter range appropriate for 1 kΩ
and repeat these steps on R2 to verify its function.
To test SPDT switch S9, put S9 in the up position and connect an ohmmeter to S9-1 and S9-
2. The ohmmeter should read 0 Ω. When the switch is brought to the down position, an open
circuit should be indicated. Move the ohmmeter lead from S9-1 to S9-3 and observe a short
circuit with S9 down, and an open with S9 up. These steps can be repeated on S10 to test its
functions.
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