3340 VCO DIY GUIDE
Best you check the iBOMs for collecting parts! I´m not using any exotic parts, mostly common stuff 😉
All pots are linear “B”
iBOM
Step 1 – Resistors (Mainboard)
Follow the BOM and its designator “R”. You see, i´m using vertical allignment to save some space. Orientation doesn´t matter.
Step 2 – Capacitors
You got metal film, electrolytic and a polystrene one. Make sure you flatten down the electrolytic ones, else you will have a bad time with attaching the panel! The poly cap can be a metal film as i´ve already seen. This guy is meant to keep tuning stability with changing outer temperature. I think if you don´t travel from the sahara to the north pole constantly, a metal film will be fine.
Step 3 – IC Sockets
You can mount ICs directly to the PCB, but i´m highly not advicing to! You will find a mark on the PCB to place the right orientation. Make sure they sit plane and tight where they should. First solder two outer legs and check the fitting. SOCKETS CAN SAVE YOUR LIVE(time)
Step 4 – Pin Connectors & Power Header
The 2×8 headers must be mounted in between the PCBs. Which one is female or male doesn´t matter, but make sure you attach them plain and straight.
The 2×5 power header MUST be soldered on the other side! If you use a shrouded one check the orientation!
Step 5 – Trim Pots
The footprints are for 3296X, if you use 3296W flip the orientation. Else the trim pots will work inverted!
Step 6 – Pin Connectors (Component Board)
Before soldering squeeze the two boards together to make sure the headers correspond together! AND put them on the correct layer!
Step 7 – LED and Resistor
Ok, that´s easy … if you put the long leg of the LED into the round hole … :p
Step 8 – Potentiometers
Finally some fun parts 🙂
Due to my chosen design the fine tune pot is a T18 shaft. For the course pot i´m using a 19mm knob. Make sure they´re all placed clean. First solder one leg of each to see if they sit well.
Step 9 – Thonkiconns
I´m placing the thonkiconns as final step with attached panel. This way there is no glitch that issues the smoothnes of the Song Huei pots and the panel fits softly.
Step 10 – Final Assembly and checking (unpowered!)
So, here we are. If everything went fine this unit should already do its oscillator thang. If you have placed the ICs 😀
BUT, before powering check the power pins if there is any short!
After powering the LED should glow and nothing should smell like fried banana!
Step 11 – Tuning (the painful process, not …)
Don´t worry! But you want your oscillator to act in a musical manner, don´t you …!? 🙂
The tuning process of this circuit is “always” the same. Before explaining this for the 1.000.000 time, i´m giving you some content on the hand. Once you got it becomes simple.
All you need is a source that gives CV notes, something like a beatstep or any other sequencer that gives quantized CV. And a tool to measure the frequency of the outputs, something like an OT1 or a Mordax Data or a guitar tuner with audio input. (Euroack Level 🔥!!!)
The clue is to get it stable over 6 octaves at least. This unit should give 7 octaves minimum 😉
Additionally you got two trim pots. One for the initial center position of the course knob. One for the range of the course knob.
With the “octave trimmmer” you can set individual octave sweeps when fully turned up or down 😉
