Elecraft KRX3 User Manual download pdf (Page 18)

Plug the aux DSP board into the main DSP board by mating P52 and P53 on the aux DSP board (at the

narrow end) with J52 and J53 on the main DSP board. When seated, the connectors should be fully engaged

with the aux DSP board resting against the standoffs with the holes in the board aligned for the screws (See

Figure 18). Note that a two-row 10-pin connector at the top of the aux DSP board does not mate with anything

on the main DSP board. That is normal. Attach the boards with three 4-40 1/4” (6.4 mm) nylon screws or the

nylon screws you trimmed to length earlier (see Figure 13). Place a split lock washer under each screw head. Do

not place washers between the standoff and the pc board. Be careful tightening the nylon screws. Their threads

strip easily!

Figure 18. Mating the Main and Auxiliary DSP Boards.

Mount the DSP board assembly on the front panel board as follows.

ESD SENSITIVE: Wear a grounded wrist strap or touch an unpainted metal ground

before touching the DSP or front panel boards.

Place the front panel assembly face down on a soft, clean surface to protect the finish. The back

side of the front panel board should be facing upward.

Position the large flat washer on the inside of the front panel over the PHONES jack hole (see

Figure 10 on page 14). This is easily done by sliding the washer into place from the end of the

front panel.

Gently position the DSP board assembly on the front panel board so that the large jack fits

through the cutout in the front panel board with the threaded section passing through the large

flat washer and the circular opening in the front panel. Adjust the position of the board as

needed so you can see the standoffs on the front panel board lined up with the screw holes in the

main DSP board. The nylon standoff next to J51 rests against the front panel board, but is not

attached to it.

Pick up the assembly while holding the DSP assembly board in place and inspect the position of

the two male plugs on the DSP board. They should mate with J31 and J32 on the front panel

board. J31 is near the encoder for VFO A and J32 is between the two dual potentiometers.

Adjust the DSP board’s position as needed so the pins enter the corresponding holes in the

sockets on the front panel board.

Squeeze the boards together while ensuring the pins are mating with the connectors until the

DSP board is resting against the three standoffs on the back of the front panel board that you

installed earlier. The two connectors will not mate completely. About 1/4” (6.4mm) of the pins

may be visible when the DSP board is positioned against the standoffs.

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Elecraft KRX3 User Manual Page 18