Synthrotek M/DIV

M/DIV is a 4hp CV-controlled dual clock multiplier/divider with tap tempo. The M/DIV has three clock outputs: a master clock and two multiplied or divided clocks. Each channel can do either multiplication or division with the flip of a switch. Here’s what comes in the kit.

All the parts coming with the M/DIV kit
M/DIV Visual BOM
M/DIV Quick Start Guide

And that is it. No construction steps are give, though there are demo and build videos.

Construction

The orientation of the 20-pin right-angle header that connects the two boards was a bit confusing. The demo and build videos were essential to getting it correct. A couple of photos of the finished module would have helped a lot. The first step was building the main component board. The first thing you notice is that the 1/4 watt resistor leads have to be bent right at the body to fit the board. The use of 1/8 watters would have made it easier. The only parts I substituted were the 0.1uf bypass caps and the electrolytic caps. I’m sure the originals would work fine, but I had some that I thought were better quality.

I could solder the main board with organic flux for a very clean build. Notice the spot for J4, a jumper header that is not installed. And notice that the two IC sockets have opposite orientations. Use no-clean solder on the pot board.

M/DIV Pot Board back side
M/DIV pot board assembled to panel
Another view of the assembled pot board and panel

To fit the sockets, first affix the standoff to the PC board using the 2.5mm screw. I added a lockwasher under the screw head. Insert all the sockets and put nuts on a few of them. Hold the bottom sockets flush to the board when soldering. Now the rest can be soldered. Then remove the nuts and separate the panel, so that you can install the push button switch, the header, and the slide pots. Insert the LED (long lead to +) before assembling the panel again.

The trickiest part of the build is fitting the right-angle header. Why? Because one of the slide pots mounts on the other side, right over the solder points for the header. I made a mistake by soldering the header pins and then cutting them off. This didn’t leave clearance for the slide pot! I had to remove solder from all of the header pins and cut them flush and resolder. Much better if the pins are first cut flush and then soldered.

Assembled module

Now notice how the 20-pin header is spaced out about 1mm from the pot board. The distance isn’t critical, but there needs to be a bit of space to avoid having the protruding socket leads hitting the edge of the main board.

Finished front panel

The panel is made of PC board material and the markings look crappy. I used knurled jack nuts, rather than the hex nuts that came with the kit. The switches do not fasten to the panel; they are just soldered into the PC board.

The M/DIV works as described and provides a lot of clock functionality in only 4hp. I don’t mind too much that it’s not pretty.

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