Elecraft AF1 Audio Filter User Manual
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Assembly Procedure
The finished audio filter is shown in Figure 1. The knobs were left off to better show the components on the board. We
recommend you follow the assembly procedure below, and refer to this figure as needed.
Figure 1. Assembled Audio Filter.
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Use adequate ventilation when soldering; avoid inhaling smoke or fumes. Always wash your hands after
handling solder, as lead residue is highly toxic.
When applying solder, use the minimum amount required to surround the component lead and make good contact with its
printed-circuit pad. You don't need a "fillet" (build-up) of solder. This will avoid unwanted solder bridges and any need to
clean the PC boards.
The solder must flow onto both the component lead and its PC board pad. To ensure that both will be heated at the same time,
the tip of the iron should contact both the component lead and the PC board pad before solder is applied.
Solder joints should be clean and shiny. If a joint appears dull or has fine cracks, it is probably cold. Cold solder joints should
be cleaned and re-soldered. First, use solder wick (desoldering braid) to remove the old solder. Then apply fresh solder. If
you have many cold solder joints, it probably indicates that your soldering iron temperature is too low, or that the tip or
solder itself is defective.
Install the fixed resistors listed below. Position each resistor within the outline on the PC board, solder and trim the leads
flush on the bottom. If you position the board so the legends are right side up, you can work from left to right across the
board following the order given below. Save one of the clipped leads. You will use it to make a ground test point later.
__ R18, 22k (red-red-org)
__ R2, 1K (brn-blk-red)
__ R7, 1K (brn-blk-red)
__ R4, 1K (brn-blk-red)
__ R1, 1.5k (brn-grn-blk-brn)
__ R6, 10k (brn-blk-org)
__ R17, 360k (org-blu-yel)
__ R14, 1.0k (brn-blk-red)
__ R3, 15k (brn-grn-org)
__ R13, 360k (org-blu-yel)
__ R8, 180k (brn-gry-yel)
__ R9, 680Ω ((blu-gry-brn)
__ R12, 680Ω ((blu-gry-brn)
__ R11, 180k (brn-gry-yel)
__ R16, 10Ω (brn-blk-blk)