Preparing the Mixer PCB (3 GHz U/D Converter) for Assembly
When the boards were made, the "resist" material accidentally was left
over the pads and traces
in some locations. This will have to be removed before you can solder the surface-mounted
components or external connections to the board.
Refer to the photo of the board and the schematic as you do this removal. You
will need an
X-acto knife to do the job, and take care to not scrape too deeply. The blade with the rounded
end works well for this. You need to expose the bare metal of the traces, and some of the
groundplane material on the board where the mixer component goes.
View the board with the mixer component at the top.
Remove resist from the following locations on the board:
1. The three mixer component terminals:
Left side - above and to the right of the "LO" label, inside the mixer outline.
Bottom - above and to the right of the "IF" label, inside the mixer outline.
Right side- below and to the left of the "RF" label, inside the mixer outline.
2. Some of the ground plane inside the mixer outline. Hold the mixer in position,
its three terminal pads on the board. Observe where the mixer body covers the board and scrape
enough resist from the board groundplane so that you can (later) solder the mixer edges to the
3. Left side of board: The "LO" input trace at board edge just below the "LO" label.
4. Left side of board: The "12RT" terminal just to the right of the "12RT" label.
5. Left side of board: The "IF I/O terminal at board edge just below the "IF I/O" label.
6. Bottom left of board: The "12TV" terminal just to right of "12TV" label.
7. Bottom of board at edge: The "TX IF" trace just left of the "TX IF" label.
8. Right side of board: The "12T" terminal just below the "12T" label.
9. Right side of board: The "12R" terminal just above the "12R" label.
10. Right side of board at edge: The "RX IF" trace below and to right of the "RX IF" label.
When you are finished, use an ohmmeter to check that continuity exists between
following locations, and does not exist to ground:
1."LO IN" trace and left pad of R11 location
2."12RT" terminal and bottom pad of C18 location
3."IF I/O" trace and top pad of C6 location
4."12TV" terminal and bottom pad of R8 location
5."TX IF" trace and bottom pad of C11 location
6."12T" terminal and top pad of C17 location
7."12R" terminal and right pad of R7 location
8."RX IF" trace and right pad of C8 location