Elenco Digital / Analog Trainer - Manual (Page 6)

-5-
TESTING THE XK-150 DIGITAL ANALOG TRAINER
The following paragraphs give detailed instructions on testing the digital / analog trainer.
Note that in the XK-150 trainer there are five major functions, (1) Power Supply (2) Logic Indicators (3) Function
Generator (4) Logic Switches and (5) Data Switches. We shall proceed in testing out each section.
POWER SUPPLY TESTING
Plug the trainer into 120VAC outlet and set the power switch to the “ON” position. The red LED will light when
the unit is on. Set the the knobs for the +15 and --15 volts fully counter clock wise. Obtain a digital voltmeter
and measure the voltage at POS (+15V) binding post. The voltage should be approximately 1.25 volts. Measure
the voltage at the NEG (--15V) binding post. The voltage should be approximately --1.25 volts. Then turn both
knobs fully clockwise and measure the outputs again. The outputs voltage should be between 14.5 to 16 volts.
Short the POS binding post or the NEG binding post to the GND binding post. DO NOT short the positive and
negative posts together. The voltage regulators will turn off and the voltage drops to zero. Remove the shorts
and voltage should recover.
Set the +15 volt supply to 15 volt. If you have a 60 ohm 4 watt resistor, place it across the POS and GND binding
posts. The output of the 15V supply should not change more than .15 volts. In making this test, the voltmeter
leads should be clipped to the terminal directly and not to the load leads. This is to prevent errors in voltage drop
due to contact resistance of the load. Do the same for the -15V output, connecting the resistor between the NEG
and GND binding posts. The output should not change more than .15 volts.
Measure the voltage at the +5V output. The voltage should read between 4.75 and 5.25 volts. Short the output
to the GND binding post. The voltage regulators will turn off and the voltage drops to zero. Remove the short
and voltage should recover. Place a 20
Ω
, 2 watt resistor from the output to the GND binding post and measure
the voltage. Again, the output should not change more than .15 volts.
Set you meter to measure AC volts. Measure the AC voltage across the 1 and 3 terminal of the ac output. The
voltage should be about 30VAC. Move one of the leads to the 2 terminal the the voltage should be about 15VAC.
WARNING!! DO NOT SHORT THE AC OUTPUT TO GND.
TESTING THE FUNCTION GENERATOR
To test the function generator, you will need an oscilloscope. Connect the scope to the SINE wave binding post
and the ground clip to the GND binding post. Set the switch the to 1X position. Your scope should show a sine
wave with an output of about 4Vpp. Turn the frequency control, the frequency should vary between 200 and
2000 hertz. Turn the switch to 10X and vary the frequency control. The frequency should vary between 2,000
and 20,000 hertz. Check the square wave output in the same manner. The amplitude of should be 12Vpp.
TESTING THE CLOCK
If your scope is a dual trace, connect one probe to the +CLOCK terminal and the other to the --CLOCK terminal.
Set the switch the 1kHz. You will note the two frequencies are 180 degrees out of phase. Check the 1kHz and
100kHz settings. Check the 60Hz terminal a for 60Hz square wave signal.
If no scope is available, connect a wire from the +CLOCK terminal to the “7” LED logic indicator terminal.
Connect another wire from the --CLOCK terminal to the “6” LED logic indicator. Set the clock frequency switch
to 1 hertz. The two LEDs should blink alternately. In the 1kHz and 100kHz position, both LEDs will be on.
Remove the wire from the +CLOCK terminal and connect it to the 60Hz terminal. The LED should be on.