Phew! The resistors are all soldered. The board has a few
hundred of them, so there was quite a bit of soldering.
Over the next several months I'll be building what is definitely
my most complex electronics project to date: the MFOS (Music From
Sound Lab Ultimate,
Ultimate Expander and (if Santa brings one)
Sound Lab Mini-Synth Mark II, likely all in the same home-made
wooden case, side by side. The Ultimate and Expander are together a
3 oscillator monophonic true analog synthesizer with filters,
envelopment generator, ring modulator, sample and hold and more.
You patch between the different logical modules using banana
cables, so it's a bit of a self-contained modular synthesizer. The
Mark II is smaller, newer, and has a few fewer features, but a
sound of its own. You also patch that with banana cables, and can
integrate the two. This blog post is another in the series.
Previous posts include:
Here's an image of the board with all the resistors in place. In
the oscillator section to the left, one resistor in each of the
three is not used. I marked it with a silver sharpie. In addition,
a second resistor is left empty in each oscillator if you use the
temperature compensating resistors. Since I'm going that route,
that slot is empty and marked with a brown sharpie.
Overall the resistor soldering was enjoyable but monotonous. The
only problem I ran into was a mistake I made when ordering. When I
ordered the 3M resistors, I accidentally ordered 1/8W instead of
1/4W. Looking at inventory at Mouser, I realize why: they have no
small quantities available for 1/4w 3M resistors. It's possible the
board only needs 1/8W (I haven't calculated it), but rather than
take any chances, I put two 1/8W 3M resistors in parallel in the
two spots that required 1/4W 3M resistors.
NOTE: Don't do this. I was only thinking about wattage,
but didn't realize that resistance drops when you do this. The two
3M resistors end up producing only 1.5M actual resistance. Thanks
to Michael in the comments for saving me some annoying debugging
Other than that, I forgot to swap out two replacement values for
R184 and R189 as recommended in the MFOS page. I did that after I
took the photo.
I could have just ordered some replacements, but I really didn't
feel like waiting, or wasting the money. Here's another shot of the
board with resistors in place.
Once everything is assembled, I'll set up some better lighting
and take a few wallpaper-quality shots of the board. Here are some
opinions on soldering all these resistors:
I actually found it relaxing to solder all those (well, once I
got a decent fume removing fan). Resistors are pretty immune to all
types of crappy techniques: other than making sure you have the
right values, you don't have to worry a whole lot about them.
Soldering transistors, on the other hand…
Next up will likely be capacitors or the trimmer pots.