Roland MC-202 Mods7 - Rackmounting

As I've said before, I intended to rackmount this MC-202 right from the start, so a lot of planning has gone into it. In fact this has become one huge project - it is much harder than i thought, as it involves a lot (I mean LOTS) of wiring / re-wiring.

Since it already has the Modular Upgrade there, it's even harder working on the PCB with all those flat cable wires attached. It's very easy to make a little mistake and things would go wrong. Although i did shorten and re-wired most of the "modular" wires, I actually did these 1st before even removing any sliders or pots.
The sliders/pots are there and easy to re-solder wires to, but the mod wires are not.

1. CASE

I could have done this in a 2u case, or a large / deep 1u case. But I just don't feel like drilling metal - still after doing the Korg 800DV and MS-20, maybe i still got that drilling phobia, or maybe it's because i got complaints from upstairs while i was drilling the Jen Rack panel....

So i chose the 1u ABS PLASTIC case again, the same one I did the PAiA Fatman in.

PCB and Flat-cable Cutting up

The actual PCB with the Switchboard and the Sync-board won't fit inside the short 1u i'm using.... so i need to remove them somehow....

The 1st thing i actually tried, was cutting the internal flat cables that link the main PCB to the Switchboard. Then test the 202 with external CV/Gate to see if it works. As I've expected, the analogue/synth section works without the switchboard.

Then, looking at the schematics, i find that the Sync-board is probably not needed, although it does have a CAL switch... but it seems that the CAL switch only affects CV that goes thru the internal sequencer. Since the CV IN is already modded to bypass that, so the CAL trimmer is not needed as well, which means the whole Sync-board can be removed.

Well, so after that I have an Empty 202 case, Switchboard PCB + Rubber Keys, LCD, and also the Sync-board as spares. I actually sold these on eBay...

2. Power Supply

Although the MC-202 can be powered by 6x 1.5V batteries or a 9V DC adapter, I read somewhere that the actual power input can take up to 17V - 18V. Running it above 15V not only reduces NOISE and also it will use only around 100mA - 150mA.

I also planned to add an internal Midi-CV converter, so i'd need a +/-15V anyway.

A small chassis transformer was used,
this is actually a 3VA 12V + 3VA 12V transformer.

PSU Circuit

I have the schematics of the Korg MS-02 which has a very simple PSU circuit, using 7815 and 7915.

So i built a PSU board around this.

Funny that when i searched on the web, I found that the ASM-1 PSU board is very similar to this...

Click to Enlarge

Disclaimer: I'm not responsible for anything if you try this out and it blows up anything. The circuit / stripboard might contain errors. Also, this is to deal with high voltage electricity, don't bloody electrify yourself!!

I don't do custom PCBs, so I do everything in stripboards/veroboards.

This is the same PSU circuit on a 10x30 stripboard.

(Click image to enlarge
or do a Save As...)

Mounting

If i have the 202 PCB on the right, I have enough space on the left for the transformer and the PSU board and the midi interface...

3. IEC Mains Socket & Fuse

Well, now that we have the internal PSU, we don't need to an external power adapter.
An IEC Mains Socket is fitted, along with a Fuse holder and Fuse (I use quick-blow 1A fuses, 500mA should also be suitable).

Note:
To make the IEC Mains Inlet hole, I use a screwing hand tool, which is an M10 Radius Hand Hole Cutter, 28x21mm (RS Cat.#543-614 or or 541-501), with matching 10A Snap In PCB Mount IEC 320 Plug Socket (311-8031 or 488-191).

4. Front Panel Pots and Wiring

It took me many nights to do this, taking off all the sliders on the 202 PCB and then re-wiring to the pots on the front panel.

Pots:
This is a summary of Pots that are needed:

LFO Rate	100K A
LFO Delay	500K B
VCO MOD	100K A
VCO PW	10K B
Source Mixer	100K B x2
VCF Freq	100K B
VCF Res	100K B
VCF ENV	100K B
VCF LFO MOD	100K A
VCF KYBD	100K B
ENV A	250K A
ENV D	1M B
ENV S	100K B
ENV R	1M A
Tune	10K B
Volume	100K A
Accent	100K B
Portamento	1M A
Audio In, VCO TRI	100K B x2
Overdrive Mod	100K B x2

Switches:
1 Toggle Switch for the VCA ENV/GATE, 1 Rotary for the VCO Range Select.
Since the 1u is very cramp/tight in space, putting more rotary switches is not a good idea.
From the Oakley Moog Rogue Rack, I've learnt one thing - use 2 switches for any 3 position slider switch.
So, we can actually use 2 small toggle switches for say the Pulse Width Select, or the Sub-Osc Octave.

Further switches are needed for toggle between internal and "Midi Add CV" for the LFO MOD, VCF Cutoff and the Feedback Mod.

Front Panel Layout

The front panel layout is similar to the original MC-202 panel...

POWER, Midi Indicator, Midi Learn Sw, VOLUME, Tune, Accent, Acc Sw, Portamento

Note:
To make the square-ish hole for these illuminating Power Switch, another one of these Hand Hole Cutter is needed. This one is the M10 rectangular hole cutter,22x19.6mm, RS Code: 600-161.
The Power Switch is one of those DPST green (or red) illuminated rocker switch, 10A/4A.
RS Codes are Green: 318-070, Red: 318-064

LFO: LED, LFO Rate, LFO Delay, VCO Range, MOD, PW, PW Select

VCO: VCO Range, MOD, PW, PW Select

MIXER: Sqr/Pulse, Saw, Sub-Osc, Sub-Osc Oct, Ext Audio, Tri, Feedback Sw.

VCF: Freq, Reso, Midi Sw, VCF MOD, Env, Kybd

VCA: ENV/GATE Sw, Overdrive1, Overdrive2; ENV: A, D, S, R

I actually planned this with Schaeffer's Front Panel Designer. My template is here (fpd file).

What I've actually done is not exactly as what's on the fpd file, but it's near enough.

IMPORTANT Wiring NOTE

I actually had a common EARTH wiring between the pots, so to save me wiring 10 - 20 ground wires from the PCB to the front panel pots....
However, after that when i power up the 202, it all went funny... it is then i realized one thing.... The GROUNDs on the 202 PCB are not common. They're interlinked via the ground pins of the pots and also the mounting brackets of the pots and the switches!
SO: MAKE SURE ALL THE GROUND ON THE PCB ARE ACTUALLY LINKED UP AND CONDUCTING!

5. Rear Panel Sockets

Basically, Audio Out and Audio In are 1/4" Jack sockets. I didn't do a VCA Audio In.
The rest, are straight from the modular sockets...

Audio Out / Audio In / Modular Output Sockets

CV Outputs and the various CV Inputs

Note: For some of the switching sockets, since I don't have the internal sequencer anymore, there's no need for me to wire the CV from the internal to the socket. Instead, I wired the CV Outs / gate Outs from the Midi-CV Interface, so, any thing external that plugs into these socket will still work (and disable the internal midi cv).

CV/Gate IN, Midi In and the Fuse and IEC Mains Socket

OVERALL RACKMOUNTING COMMENTS:

	i must have wired/re-wired over 120+ wires....
	Full credits to Roland, cramping so much stuff into such a small PCB - not until i started this project, i never knew the MC-202 is this complex in design....
	How i wish there could be a small Midi-2-CV that can handle all those CV In's...
	This 1u is still neat, at least i don't have to worry about the modular socket box (or accidentally pull out any of the flat cables)

	Synths
	*Last Updated:*
Roland MC-202 Rack *(Midi-fied)*

MODS 7 - Rackmounting
\| Synth Index \| MC-202 \| \| MC-202 Mods1 \| MC-202 Mods2 \| MC-202 Mods3 \| MC-202 Mods4 \| MC-202 Mods5 \| \| MC-202 Mods6 \| MC-202 Rack \| MC-202 Midi \| MC-202 Soundz \|


\| Case \| PSU \| IEC \| Front \| Rear \|