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CAUTION:
Do not connect the alligator clips to any AC power source or to DC power source greater than
35VDC. Failure to comply to this warning may result in damage to this instrument.
TESTING YOUR DIGITAL PROBE
Checking out your Logic Probe for proper operation is
fairly easy. All that is needed is a 9V battery or other DC
power source (5-10V). Connect the red alligator clip to
the positive terminal of the battery and the black clip to
the negative terminal. Set the PULSE-MEM switch to the
PULSE position and the TTL-CMOS switch to the TTL
position. Touch the probe tip to the positive side of the
battery, the PULSE LED should blink once and the HIGH
LED should light up. Place the probe tip to the negative
terminal and the LOW LED should light up. To check the
operation of the memory switch, set the PULSE-MEM
switch to the MEM position and set the TTL-CMOS
switch to the TTL position. Now touch the probe tip to the
positive side of the battery. The PULSE LED should
Condition
No LED's light up.
HIGH LED or LOW LED never lights.
HIGH or LOW LED always on.
Pulse LED always on.
PULSE LED never flashes.
All LED's flash.
FOIL SIDE OF PC BOARD
TROUBLESHOOTING CHART
Possible Cause
Power cord
Check U1, C7, or D6.
Check U1.
Test LED by shorting pins 1, 2, or 14 to negative supply.
Check U1, R9 to R15.
Check Q3 - Q5, U1.
Check LED 3, Q1 - Q4, D3, D4.
Noise on power line.
-9-
come on and stay on until the switch is flipped back to the
pulse position. No LED's should light up when the tip is
not touching anything (open circuit).
The logic probe should operate at the following logic
levels when the power supply voltage is precisely set to
5VDC.
DTL/TTL Position
CMOS Position
Logic 0 - under 0.8V + 0.1V
Logic 1 - above 2.3V + 0.25V
Logic 0 - under 1.5V + 0.2V
Logic 1 - above 3.5V + 0.35V
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