BOM and Build Guide for ACCESS (v1.3F):
Click for BOM
| Qty | Value | Parts |
|---|---|---|
| 1 | 10-Pin Box Header | CONN7 |
| 1 | TL072 op amp | IC6 |
| 1 | TL431 reference | IC7 |
| 2 | 1N4001 diode | D1, D2 |
| 2 | 68R ferrite | FB1, FB2 |
| 2 | 4.99K resistor | R49, RS1 |
| 4 | 10u/25v capacitor | C2, C3, C4, C5 |
| 5 | LM6172 op amp | IC1, IC2, IC3, IC4, IC5 |
| 6 | Befaco Nuts (RGB) | (2x Red, 2x Green, 2x Blue) |
| 6 | Befaco Pot Nuts | - |
| 6 | Thonk Micro Knobs T18 shaft (RGB) | (2x Red, 2x Green, 2x Blue) |
| 6 | PJ302M jacks | CONN1 – CONN6 |
| 6 | 100K resistor | R1, R2, R3, R5, R7, R9 |
| 6 | B10K right angle pot | VR1, VR2, VR3, VR4, VR5, VR6 |
| 14 | 100n capacitor | C1, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18 |
| 15 | 499ohm resistor | R4, R6, R8, R10, R11, R12, R14, R15, R16, R31, R33, R35, R46, R47, R48 |
| 16 | 1K resistor | R13, R19, R20, R21, R22, R23, R24, R32, R34, R36, R37, R38, R39, R52, R53, RF1 |
| 1 | Pcb set | - |
| 1 | 10-16 power ribbon | - |
SPECIAL NOTES for BOM:
- All resistors are 1/4Watt, 1% metal film resistors.
- Typical “Davies” knobs are too thick for comfort. Please use knobs linked above.
- Potentiometers must be Linear-taper (B), 10Kohm, T18 shaft.
Click for Build Guide
Part 1: ACCESS (PCB 1/3)
Step 0.
Locate the board labelled (PCB 1/3) from the bunch. This board also lists the BOM for the whole module.
Step 1.
Here we will place the first nine 499ohm resistors, all labelled 499R. I will personally place all resistors before soldering them all at once.
Step 2.
Now populate six 1K resistors.
Step 3.
And now you will populate six 100K resistors. It is at this point I will solder and clip all of the resistors.
Step 4.
Populate six 100nF (0.1uF) capacitors.
Step 5.
Two electrolytic caps now. Both are 10uF rated at 50V, although you can get away with 25V if you have them. Be sure to take care to place them correctly because they are polarized. You will find a stripe on your caps which identifies the negative lead.
Step 6.
Six pots and six jacks. Each pot is a right angle, 10Kohm, T18 shaft with a linear taper.
Step 7.
Finally, we will solder in three LM6172 op amps. Pin one of each chip is marked with a circle or divot. Make sure to place these pins in the square vias on the board. Afterward, we may move on to (PCB 2/3).
Part 2: ACCESS (PCB 2/3)
Step 0.
Locate (PCB 2/3).
Step 1.
Populate six 499R resistors.
Step 2.
Now populate eight 1K resistors. Ignore “RF1” and RS1" as we will come back the these below.
Step 3.
Next place the 4.99K resistor.
Step 4.
Now we will populate RS1 and RF1 which are printed on the board. These set the biasing reference.
Place a 1K resistor into RF1 and a 4.99K into RS1.
Step 5.
Now we can solder eight 100nF caps, both ferrite beads and both diodes.
The diodes are polarized, so we must line up the stripe on your diode with the stripe on your PCB.
Step 6.
Again, the next parts are polarized. Both 10uF caps must be lined up properly. Place the positive lead into the via marked with e “+.”
Step 7.
Now solder the power connector. This part has a notch which faces out from the board’s edge. It is also clearly marked in the board’s print.
Step 8.
Place your pots and jacks into the board but don’t solder them just yet. Carefully install the faceplate and hand tighten a nut onto each jack and pot. Now make sure each part is properly lined up and then solder each of the pots and jacks. Remove the faceplate again.
Step 9.
Now we can populate the active parts. Here we will solder the TL431 and TL072.
Step 10.
And finally, solder in both remaining LM6172’s.
Part 3: ACCESS (PCB 3/3)
Step 1.
For the final part of the build, install both PCBs into the faceplate. Only finger-tighten a few nuts since we will want to clean the PCBs once soldering is finished.
PCB 2 will go above PCB 1. Notice how the power connector is accessible.
Also, pull out one 6-pin stackable header and clip off a 6-pin section from your collection of male pin headers.
Step 2.
Put the stackable header and male pin header together. Carefully insert the long-side into PCB 1 and let it fall into place.
Next turn the module over and the pin header will fall to the other side. Adjust it’s placement so that both sides are through both PCBs as seen below:
Step 3.
Go ahead and solder all 12 pins; that is, 2 sides of the 6-pin header. Make sure you don’t miss any.
At this point, I will take the PCBs back out of the faceplate and clean them up with alcohol.
After you’ve done that and inspected your solder for any visible errors, we can finish this up.
Step 4.
At long last we can put the PCBs back into the faceplate and screw it all together.
Both top jacks will get a red befaco bananut.
Both middle jacks will get a green benenut.
And both bottom jacks will get a blue bananut.
All six pots will be tightened down with a black pot-nut, also from befaco.
All of these nuts will need to be fastened down with the special befaco-nut tool.
Lastly, we can stick the knobs on. We will be using six of Thonk’s micro-knobs.
Again: two reds on top, two green in the middle and two blue on the bottom pots.
Find a power ribbon cable and test it out! The knob positions shown below are for no attenuation and 0V bias. It is the neutral THRU setting.
Enjoy.
