SL-1176-KIT:  Connecting the Boards

All of printed circuit boards (PCBs) interconnect via the "J headers," the source and destinations are indicated on the schematics. The "male" headers are soldered into the boards. The "female" receptacles plug into the headers. Receptacles require 24-gauge wire to be punched into the slots. Normally, this is accomplished with a crimp tool, although these tools are quite expensive, so we'll take the DIY approach.

Wires can be manually punched into the receptacles with a screwdriver. It just takes a little practice and a bit more time… A small flat blade screwdriver works best, one with a blunt tip is preferable over a sharp blade for two reasons. One, the blunt tip is less likely to cut you if you slip off the receptacle. Two, a sharp tip will cut into the insulation of the wire.

Begin by holding the receptacle against your workbench or a board. Place the wire into the slot. Leave the insulation on the wire instead of stripping it. While holding the receptacle firmly, press the screwdriver tip on top of the wire so that the wire is forced into the barbs of the receptacle. You may need to press a couple of times in a few different spots to make the wire seat in the barbs. The barbs automatically cut the insulation as the wire is pressed into them. This is called "insulation displacement." The barbs then make contact with the wire inside while the insulation keeps pressure on the wire to keep a tight contact. 

PUNCH MOST
Once connectors are attached at each end, it’s a good idea to check continuity. Do this by touching your ohmmeter probes to the metal at the top of each receptacle to confirm contact. If there is no continuity, re-seat the wire with a screwdriver. You may want to buy a few extra connectors and practice first.

SOLDER ONE
There is one header that cannot have the wires punched into its receptacle. J3 on the output amp PCB connects to the output transformer leads. These wires are a smaller gauge and will not seat tightly in the receptacle barbs. You will need to strip back about 3/16" of the insulation and tin the wires. Also tin the wells of the receptacle barbs. A fine tip solder iron is needed here to get in between the plastic. A little plastic will melt or burn. Try to get the solder to flow into the wells. Then heat up the solder filled wells and solder in the stripped and tinned leads for the transformer following the pin-outs from the output amp schematics.

BEFORE cutting wires, make sure to be generous when measuring the lengths needed to reach between them, then add 3-4 inches because some length will be lost when twisting the wires together — either by hand or with a variable speed drill (more on that later). Once twisted, neatly "dress" them to their destination receptacle at the next board. 

Any vari-speed or hand-drill makes short work of twisting wires together. Simply take the wires to be twisted in a bundle, put one end in the drill chuck and snug down the collet. Run the drill in slow speed and hold the other end of the wires in your other hand. The wires will twist together neatly and quickly.

WIRING THE FRONT PANEL POTS

Some boards require connection to the front panel pots. The header connections to specific pot legs are detailed in the schematics. Click here to see how Scott positioned the PCBs in his prototype and dressed the cabling.

For help with schematic reading, look at the side-chain schematic at header J-3 as an example. Pin-1 goes to leg-3 of the attack pot, pin-2 to the wiper (center) and pin-3 to leg-1. If you look at the pots from behind (shaft points away from you), with the legs pointing down, leg-1 is left, wiper is center and leg-3 is on the right. That’s how all pot connections are labeled. It’s not a necessarily "convention," but a system Scott used to keep connections straight.
 


Wiring the front panel pots