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The PB-503A may be checked out for proper operation by making a few simple measurements
and connections. Begin by connecting the AC line cord to a suitable receptacle. The AC power
indicator should light when the power switch is turned on. Using a DC voltmeter, check for +5 V
between the ground terminal and the +5 volt terminal. Repeat the measurement for the positive
(+) variable supply terminal and the negative (-) variable supply terminal. Check the variability
of each supply by turning the appropriate adjustment knob.
To test the logic indicators, switch the +5/+V operating voltage switch to the +5 position. The
TTL/CMOS threshold switch can be in either position. With no input to the logic indicators, all
LEDs should be turned off. Connect one end of a jumper wire to the + 5 V terminal and the
other end to logic indicator 1; the red LED of logic indicator 1 should light. Repeat this test for
logic indicators 2 through 8. Disconnect the jumper from the +5 volt terminal and connect it to
the ground terminal. Connect the other end to logic indicator 1; the green LED of logic indicator
1 should light. Repeat this test for logic indicators 2 through 8.
Be cautious when using components which have been removed from a tape reel used in
automatic insertion equipment. Suppliers of surplus components often sell components which
are taped together in small batches. Removing the components from the tape does not always
remove the adhesive from the leads of the components. Placing a formerly taped component
into a socket connector may result in a poor electrical connection and, worse still, leave tape
adhesive in the socket. Avoid this problem by either carefully cleaning taped component leads,
clipping the taped portion of the lead off, or avoiding the use of taped components altogether.
The digital function generator may be tested by connecting its output to one of the speaker
inputs. Connect the other speaker input to the ground terminal (or one of the connectors on the
ground bus strip). Set the frequency to 60 Hz and select the square wave. Move the amplitude
control upward until you hear a tone coming from the speaker. Step through any range of
frequencies up to 20 kHz (this upper limit may vary as it depends on the user’s own hearing)
and the pitch should change. Push the waveform buttons to select sine, square, and triangle.
A changing but clearly audible tone should be heard in each position.
If an oscilloscope is available, you may check the digital function generator for proper
waveform and frequency using standard measurement techniques.
The debounced pushbuttons can be checked by connecting one side of a resistor (20Ω to
100 kΩ) to +5 volts and the other side to PB1-1, the NC point. Then connect PB1-1 to LED-1
with the Logic Ind5/+V switch in the +5 position, the red LED should light when PB1 is
pressed and the green LED should light when PB1 is released.
Checking out the PB-503A
