Anyone with any sense would just buy Tubbutec’s apparently excellent Juno-66 mod and be happy, but just for the freaks I’ve finally fixed my Juno-6 DCB interface layout so it’s now ready for sharing.

Here are the Gerbers, zipped up ready for the likes of JLCPCB:

juno-6-dcb-rev-b.zip

…and here’s the BOM.

Basically it’s this bit of the Juno-60 schematic broken out into a separate board.

Now it’s the 21st century all this could probably be replaced with some sort of microcontroller rather than having to go through all this faff, but here we are anyway. And this keeps it authentically 1982, if that matters to anyone.

Here’s the layout, featuring my usual drunken wobbly routing:

Note the annoying mixed orientation of the ICs (U1 and U4 pointing downwards, U2 and U2 upwards), yeah, I know.

The connectors on the left are all labelled and they’re in the right order to connect to the pins on the right of the Juno’s main board, which are also all labelled up. DB1 is just labelled “1”, as I wasn’t able to squeeze the rest of the letters into that bit of the PCB.

It’s powered off 5V, and there’s a header on the Juno main board for the gate outputs which includes a ground and 5V line, which is where I ended up taking the power for this board.

Just for completeness, here’s my schematic as a screenshot (and here’s the strangely massive PDF):

Given all that and you’re daft enough to still want to give a go, when I bought my boards from JLCPCB in early April, they came out as £4.89 (including postage to the UK, as an example) for 5 boards on the cheapest settings.

This is probably one of those mini-projects where you have to be very confident about opening up synths and messing around. Juno-6s are now worth a fair amount, and I’d hate anyone to kill theirs as a result of trying this board out.

I would really recommend testing the PCB outside of the Juno first; check to make sure 5V and ground aren’t shorted, and power it up from an external test power supply, and check that the outputs aren’t putting out strange voltage levels.

The original connectors were Amphenol DDK types, and are obsolete as far as I can tell. As I don’t have any original Roland DCB gear to play with (and my urge to buy an MSQ-700 has faded now the prices have gone crazy), I used a DIN connector, which is a special kind of pain in itself – I’ve never liked wiring them up.

Eventually I’ll get round to writing up the CV/gate/MIDI to DCB box as well, here’s the mildly shoddy (but practical!) box for that: