102 almost

System 100 102 clone in my kitchen

Eight years later! And still not quite finished.

OK, so buying an actual 102 took the wind out of my sails a bit, and then there were all the diversions into silly projects like “let’s make a System 700” and “let’s do a Jupiter-4 clone in a rack” which both dragged on forever and are somewhat dead at the moment, but it feels like this is… almost… nearly… there.

The wires poking out of the side hint at the genuine nightmare behind the panel. No, we’re not going to look round the back. At this point Roland were wiring straight to potentiometers, and I’ve done mostly the same. Here’s a view inside the original.

original System 100 102 wiring inside front panel

I did make small boards for each set of slide pots so that I could keep the screw fixing to the panel as unobtrusive as possible.

30mm slide potentiometer mounting circuit boards

I just about managed to scrape together slide potentiometers of the right (or near enough) values to make this. And the stalks are different lengths and materials. And they don’t even feel that nice – the big one below felt the best but I couldn’t use it in the end, I think the slide cap I was using didn’t fit.

my wonderful collection of different 30mm slide potentiometers

I actually considered going into the 30mm slide potentiometer business – or at least buying whatever minimum amount the manufacturers would sell of each value (seemingly 1000) and flogging the surplus. Thankfully they never got back to me, it would’ve been too far down the rabbit hole.

Anyway, enough complaining about wiring – these are the things I added

  • external CV input for the VCA
  • white/pink noise (straight from the model 101)
  • multiples! 
  • one-octave down SH-101-style sub-oscillator normalled to the external input socket
  • optional gate boost (the envelope is finicky about the voltage it needs to trigger)
  • switch for boosting the otherwise fairly quiet envelope output
  • plus/minus one octave switch
  • fast/medium/slow LFO ranges
  • LFO reset (already there on the model 101 version of the board)
  • switch on the S&H clock to the envelope
  • envelope fast/normal speed
  • extra cv/gate inputs on the far left

There’s probably more I could’ve bunged on it, but I was trying to keep to the look of the 102 as far as I could. Here’s the whole thing propped up a fruit bowl on our kitchen worktop.

front view of System 100 model 102 clone

I wimped out on the design slightly because I had my doubts that the printing process would be able to reproduce the (grey? green?) original colour scheme. Given that this panel cost £150 back in Nov 2019 from Schaeffer, it was strictly going to be a one-shot thing. I’d hate to think how much it’d cost now.

Now I look at it again, the absence of the block colour gives it a moody sort-of Sys100/SH-09 crossover look.

The only thing that doesn’t work yet is the phones output because I’m missing the Sansui ST-31 transformer, which seems to be hard to get hold of these days, although I’ve seen photos of boxes full of them on the internet, just to taunt me.

Here’s the usual out-of-tune bonky MC-4-driven demo that doesn’t really demo anything, mostly just showing the pulse-width mod/suboscillator and envelope fast/normal switch.

I’ve got a power supply board made up, a clone of the one in the 104, which I actually intended to make but never got round to because of the strange Sanyo TV channel selector switches which it uses. (Also it turns out that the 100M 182 is more fun)

I was going to run the whole thing off a Yamaha PA-20 and keep the transformer outside the box, just to keep it as compact as possible.

And it needs a box making up, and then it’ll be ta-daaa. Hopefully this side of 2030.

Bonus photos ‘cos I was asked: here’s the panel as it arrived, just opened up the package from Schaeffer:

System 100 102 clone panel from Schaeffer

Slightly grim photo of my panel (taken in near darkness, for some reason) balanced on top of my 101, just to show a comparison against the original 102. My version is a bit too wide, I think I must’ve take the full inside width of the original as the graphics edge-to-edge measurement.

Comparing my panel with an original 102

I need to try and shift things about to fit things in, maybe on the left of the 102 like in Jack Dangers’ studio; still need that 103 though… (and I’m working on the 100M).

I tried to keep all the slightly idiosyncratic typographical decisions like, for example WAVE(tiny space)FORM and picking out the abbreviations in PULSE WIDTH MOD and VOLTAGE CONTROLLED OSCILLATOR.

Last one; you get the idea.

102 testing

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Juno-6 DCB retrofit

Onwards with the questionable Juno-6 modification – what I thought would be some Christmas fun turned into January work, and then February annoyance.

It works now, although cleverly I’d swapped the +V and ground on the 74LS14, so it needed a bit of a bodge with a track cut and some dodgy wiring.

I couldn’t get the 4MHz clock to start with the substitute I’d perhaps naïvely used, a 7402. In the end I wimped out and bought a Toshiba TC40H002 (with a date code of 1988!) and it started up.

Once I’d got the board populated and the clock running , the next thing was to see if I got any output on the connector to the Juno. I used a program from this thread on the Arduino forums as a starter-for-ten – and it seemed like I was getting some activity on the socket, and it was within safe limits, so I felt like it was safe to connect it to the Juno connector, which is direct into the Juno’s CPU.

In the meantime, I’d heard a thing about there being a hole for a connector in the back of the Juno behind the serial number plate – and so there was:

Warning! Risk of electric chocolate

It’s a rectangular hole, looks like it was meant for a DCB-shaped connector – maybe a never-released upgrade? If you look to the left of the warning plate, you can see a couple of holes that are exactly sized for the serial number plate to move to. It all seems planned by Roland, but I’ve never seen any mention of an upgrade in literature of the time.

The DCB connector is an Amphenol DDK (D-shaped) connector, and would likely have been a pain to buy and fit. Also I found out that Kenton’s pre-made one-way DCB connector wire is £44, which put me off the whole thing. I was interested to see if a DIN socket would fit, let’s try it…

Checking that a DIN socket will fit in the DCB cutout in the Juno back panel

…success – so some cutting up metal in the garage led to this, which I’m strangely proud of:

DIN socket fitted to the back of the Juno-6 in a metal plate

It’s a little bit wonky but it’s probably the best bit of metalwork I’ve ever done. (You should see my previous crimes). The edges could’ve done with a bit more filing, but it’s near enough.

Here’s my forest-of-wires test set-up, with an old spare Arduino Duemilanove as the controller at top left – the intention is that this will live in an external box. I wanted to leave the connector on the outside of the Juno as (electrically) DCB in case I ever come across a non-stupidly-expensive MSQ-700, although chances seems slim now.

Juno-6 MIDI-to-DCB test set-up

The code from the Arduino forum sort-of worked, but I was getting some weird triggering, where the next key actually played the last note pressed. Eventually I realised that the end code (&FF) did need to be sent, and then everything fell into place.

Well, almost. I found that when the DCB board was powered off the Arduino board, everything was fine, but then when run off the 5V connector on the Juno board it wouldn’t respond to MIDI input.

I did some head-scratching, and didn’t get very far until I had a look at the DCB out on the MSQ-700:

MSQ-700 schematic DCB out

…and it turns out they’ve used a bunch of 4.5nF capacitors to ground on each output line, so I replicated this on the lines from the Arduino to my DCB connector on my breadboard, and then everything was alright.

Initially I had it going with MIDI from my MPC1000, but really I want to use it from the MC-4, so I altered the code to run off CV/gate.

Here’s a demo of it playing a fairly random tune. The first couple of bars are just one voice of the Juno, and then when the bassline comes in (on the 100M clone) there are additional wonky harmony notes played from CV2, triggered when MPX goes high.

Anyway, you get the idea.

I need to put the Arduino and supporting circuit in a box, with a switch for MIDI or CV/gate operation, and possibly a switch for mono operation to let it go as fast as possible, and also perhaps for passing CV2 through to the filter CV input.

I could do with cleaning up the code so I can bung it on here, it seems fairly reliable, but I’d like to check. I realised when playing the Juno through the MC-4 from the System 100 keyboard (which was a bit weird), that if you play legato it doesn’t pick up the change in pitch, so that needs tweaking as well.

In terms of timing, from looking at audio output only (alright, not very scientific) I’ve managed to get it down to triggering between a half and one millisecond later than a note from the 100M clone, which seems acceptable enough.

I was thinking of how that might compare to the OP-8, but I can’t find any specs or service manual for it. There’s some suggestion it uses the same Intel 8048 microprocessor as the CSQ-100 and 600, which runs at a terrifying 365kHz, give or take 10kHz. Not sure it’ll be too sharp, in that case.

Actually, thinking about it I’ve got a couple of CSQ-100s, although only one (sort of) works, and the other is dead, and bit me severely once when I tried to poke about inside with the power on.

It’ll be nice to be able to make a bit more use of the Juno – over the years I’ve mostly used it for drones, triggered it off the arpeggiator clock input, or – horror of horrors, actually had to physically play it. Shudder.

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made a cake

Fairly successful Yorkshire tea loaf, made by me

Something like a Yorkshire tea loaf – about half a kilogram of fruit soaked over-night in tea, one egg, brown sugar, some bicarb, a bit of butter, plain flour, and some brandy that I randomly threw in ‘cos it’s Christmas.

And it turned out alright! Usually everything I make turns out flat, but this one wasn’t too bad. I suspect because it has a vast amount of fruit propping it up.

Apart from that, mostly I’ve been frenziedly drawing circuit boards to order from China to try and beat the UK customs changes come January 1st.

To explain a bit – at the moment there’s an arrangement called Low Value Consignment Relief, which means that any goods imported under the value of £15 don’t attract any VAT charges, which most of my PCB orders squeeze into.

Come January 1st, HMRC are binning this arrangement and have stated that the seller will be responsible for collecting the VAT, so that makes things less fun.

There were loads of things I was going to make (a Kobol clone with 3310s subbing in for the rare SSM2050s! an MS10! the DAC/gate output board for my imagined future MC-4 ripoff that I’ve been going on about for years) but mostly I’ve been churning out boring old clones of 100m boards. Yep, even the overly-complicated looking portamento module.

Other than that, the silliest is probably this board intended for my lovely Juno-6, which is basically a copy of the DCB interface in the Juno-60. Yeah! DCB!

DIY Juno-6 DCB circuit board

At this point you’re understandably wondering why would anyone do this in this day and age, and I’d say, fair enough, it’s a bit daft.

Mostly it’s because I was too cheap to invest in a MIDI interface for this thing, but also because it’s more fun trying to work out how to get it going, even though it’ll be a bit more convoluted.

I’ve long missed the boat on buying an MSQ-700 for super-cheap, and OP-8/OP-8m are super-rare, so I guess I’ll end up writing a MIDI-to-DCB and CV/gate-to-DCB thing for an Arduino.

I’m sure it’d do-able to go from the Arduino to the Juno-6 direct, but I’m slightly nervy about knackering the MPU inside the Juno.

I opened the Juno up before I ordered the board just to see how much room I’ve got. Turns out I could easily fit some sandwiches and a banana in there as well as the board.

Inside my Juno-6, showing that there's plenty of space for an additional circuit board

Loads of room. Probably not going to do the sandwich-box mod this time round.

Also there’s a suspiciously DCB-port-shaped hole covered by a plate at the back that will hopefully mean I can avoid any drilling, because you know that’s a bad idea. Potential Christmas fun to be had anyway.

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