Step 5 – Integrated Circuits Remove from anti-static packaging, and install. Pay attention to the
orientation of the ICs, which should correspond to the marking on the silkscreen.
Step 6 – Switches
The two, 3PDT switches are mounted directly to the PC board.
IMPORTANT:
Match the outline of the
switches to the silkscreen to assure proper orientation. The switch levers are to toggle up and down, not
left-to-right! The pins are a snug fit in the PC board holes, but with firm pressure they will go through. Be
sure they bottom out against the board. Remove all hardware from the switches, and temporarily place the
top board over the switches to assure proper switch spacing before soldering into place.
( ) SW1 ( )
SW2
Step 7 – LCD Meter
The LCD meter must be modified to shift the default decimal point position. On the back of the LCD
meter, there is a set of three pairs of pads, of which one pair is shorted with a solder blob. Carefully
desolder that blob, and with solder, short out the next pair of pads adjacent to this.
When installing the LCD into the front panel, be certain that it is in the correct orientation. The four
connector pins of the LCD meter should be at the left side of the display – directly over the '4SQRP'
label on the top of the board.
Place the meter face down on your work surface, and place the board face down over it. Applying
pressure on the board near the four corners of the meter opening, Push the board down over the meter
until it rests on the meter bezel.
Separate the individual strands of the ribbon cable about 1/2” on each end, and strip back about 1/4” of
insulation on each end. Solder onto the four pads at the edge of the board. You may wish to use a
permanent marker to mark on wire of the cable to be certain its polarity is correct when attaching it. Notice
the labeling on the meter connector pins matches that on the board outputs. Wrap the matching wire around
the corresponding meter pin and solder.
Step 8 – Calibration
There is one test point on the board, above the TX connector. This is labeled TP-1. Insert a fresh 9v battery
into the battery clips, and flip the bottom switch up into the ON position. With a digital voltmeter, measure
the voltage between this test point and ground. You may use one of the hardware mounting holes in the
corners of the board as a ground point. Adjust the trim pot R33 until this voltage reads 5.00v.
( )
U1
LM337L
TO-92
( )
U2
TLC274
14-pin DIP
( )
U3
TLC555
8-pin DIP
( )
U4
TLC274
14-pin DIP
