Building
the Unit
The bill of materials
(BOM) includes the part
numbers and sources for all of
the items needed to build the
unit. The Gerber files are also
provided for the printed circuit
board (PCB). I built my unit
using a RadioShack 276-147
general-purpose PCB.
The Gerber file check
print (Figure 2) was used to
place the components and
wire-wrap wire was used to
connect any parts that were
too far apart to use the leads
to make the connection.
Also, since the PCB I
designed was two-sided, the
wire wrap allowed me to cross
over wires and make
connections that wouldn’t
have been possible on the
single side of the board (see
Figure 3).
Be careful to check all
your wiring and definitely use
the 14-pin socket for the
MCP6024 so you can replace
it if needed. Check all the
ohms between pins against the
schematic before applying the
battery, and then check the plus
input of U1D (pin 12) compared
with ground. It should read about
2. 2 volts.
The voltage across C8 should
read about 5. 4 volts. If that all
checks out, turn the power off
and install the MCP6024 being
careful to observe the pin 1
placement. If you turn it around
180 degrees, you will fry it upon
applying power.
November 2013 43
■ FIGURE 4. GTR_Pre-Amp
Lbl4M.
■ FIGURE 5. GTR_Pre-Amp Lbl3.
■ FIGURE 6. Label applied to
enclosure.
