12
installing the bulk of through hole components on the main PCB. You will also want a roll of
masking or painter’s tape on h
and to use the backer board.
8.
Build the 4027-1 VCO cores. Start with the 0805 SMD capacitors on the bottom side of the boards.
This can be done with a standard soldering iron, but be sure to dial the temperature down to
600f/315c for the caps. SMD caps can be cracked or damaged from excessive heat
–
work fast.
Apply liquid flux or flux pen (not included in kit) to the pads, place the part, and bring the iron to
it with a small bead of solder on the tip. You will need to hold the capacitor in place using tweezers
while doing this. When done, inspect under magnification. If you have a capacitance meter, you
can now measure between the pads on the 3-position header location (this is the power inlet).
You should see 100n between 0V (center) and the rails. Now, test for shorts between the pads
on the power header footprint.
The 2N3904 and 2N3906, and the 1k87 tempco are to be thermally coupled using paste.
Author’s
preference is to bring the NPN and PNP into contact with some paste between them, and then
shroud them in heat shrink. Later, bring the tempco over and with a dab of paste, lean it into the
side of the pair. It’s probably better that the two transistors are in direct contact, rather t
han
having the tempco in between them.
Do not install the pin headers at this stage.
4027-1
Resistors
Sockets
220r
3
DIP14 socket
3
1k
9
1k37
3
Capacitors
1k5
3
5p (C0G)
3
1k65
3
680p (Styrene)
3
1k87 (tempco)
3
10n (C0G)
6
3k9
3
100n (0805 X7R)
6
8k87
3
12k
6
Capacitors (electrolytic)
15k
3
10u
6
30k1
3
33k2
3
Active Components
45k3
3
CA3046
3
47k
3
2N3904
3
61k9
6
2N3906
3
68k
3
2N4125
3
100k
3
2N5459
6
121k
3
475k
3
3M3
3
Table 2 - 4027-1 VCO Cores BOM
9.
Build the PSU sub-board, starting with the SMD LDO Regulator chips. The heavy tab at the top of
them needs to be soldered to the large pad footprint. First, solder one or two of the smaller pins.
The apply a generous amount of flux to the tab, turn up your iron to 630f / 325c and heat the
tab+pad for a bit before introducing solder. Having a bit of solder on the tip of the iron will
