The ‘Hilltopper-20’ Transceiver K1SWL rev. 15 October 2018
9
• Install power diode D1 (1N5818) and bias diodes D6 and
D7 (BAT85)
. Be sure to match the
banded end of the diode to that shown on the illustration.
D7 must be installed before the
Si5351 board is installed.
• Install electrolytic cap C43 (100 µF). This part is polarity sensitive. Install so the white band on
the case faces the rear of the board.
This also corresponds to the shorter wire lead.
• Install U4 (78M05) This part is polarity sensitive. Install so that its heat-sink tab faces the rear
of the board as illustrated.
• Install capacitors C40 and C41 (marked ‘220’ or “22J”) and X6 (16.00 MHz).
I use a narrow
(0.1”) strip of paper under the crystal can to stand the crystal slightly above the board. Once at
least one of the leads is soldered, the paper is removed.
• Install resistor R18 (10K ohm, brown-black-orange-gold)
• Prepare the Si5351 board. Cut one pin off the 8-pin
header supplied with the Si5351 and mate the 7-pin
strip to the board.
Save the cut-off pin.
Make sure
the insulated portion of the header is on the
underside of the Si5351 board. Solder just one pin on
the header strip. Check your work to ensure the
header strip is firmly and squarely seated on the small
board. Once it’s OK, solder the remaining pins.
• Install resistors R14 and R15 (470 ohm, yellow-
violet-brown-gold).
• Install the Si5351 on the main circuit board. Place
the cut-off header pin) under the edge of the Si5351
board to ensure that the board is level. Tape down the
Si5351 board and the header pin using transparent
tape. Flip the board over and solder one pin of the 7-
pin strip to the main board. As before, check your work
and then solder the remaining pins. Remove and
discard the tape and single header-pin. (Cut off excess
lead length on the underside of the board.)
• Install the 28-pin IC socket at U5. The notch at one end of the socket faces the rear of the
board as shown. If you install it backwards- leave it! The socket itself is not polarity-sensitive.
• Install capacitor C24 - 470 pF (marked ‘471’)
• Install 28-pin IC U5 (ATmega328P). This device is
polarity-sensitive. The dot and or/ notch at one end of
the device must face the back of the board. You will
need to bend the IC pins gently inward to mate with the
socket. The best approach is push the IC down on a hard
surface to bend one 14-pin row at a time evenly. Once