DISCLAIMER: Follow these instructions at your own risk, and be careful. I'm not responsible for your handiwork or lack of soldering skills! And if I've made a mistake (I don't think I have, but those are famous last words), then I'm very sorry but have you heard? The story of the Golden Ninja Warrior?
This thread is a guide to setting up Python 2-based DDR games (SuperNOVA, SuperNOVA 2) on a classic DDR doubles cabinet. Note: you can't get it working on anything except for a legit DDR doubles cab. Comments, corrections and questions are encouraged. If you want to redistribute it elsewhere for whatever reason, do iiiiit.
Before anyone asks, I am not aware of any pirated or bootlegged arcade versions of SuperNOVA or SuperNOVA 2 - I imported my motherboard (and marquee and control panel) from Yahoo Auctions Japan just under a year ago (when all the JP arcades upgraded to DDR X). It's legit (albeit Japanese, not European so I wouldn't be able to put it out on location. It never officially came out in Europe anyway due to the lovely RoHS regulations).
Big shout out and thanks to my main man Zash (for acting as middleman in my quest to get an Ext I/O, and for various conversations over email and PM, for testing that the MC_PWR connection isn't needed, and for actually putting all this into practice by getting his SN2 up-and-running first [and posting pics]

). Also thanks to zorahk for clarifying info about the white security plug.
Some of the images are clickable and will take you to my flickr account, where you can get biiiiiig resolution versions. Some are not. The full set is here:
http://www.flickr.com/photos/chi-ryu/ta ... a2upgrade/"
Basic Overview:
You need the following items:
1) Python 2 unit (A.K.A. PS2-in-a-box) with DDR installed and a BLACK security plug[1].
2) Extended I/O unit (EXTIO).
3) Cabling to convert the lights and other I/O plugs into the correct format (see section III), and to provide power to the Python 2 and Ext I/O units.
4) A 100VAC power source - most likely you already have this inside your cabinet[2] (every Japanese and Asian cab I've seen has a 110/120V internal power source off the transformer, but I make no guarantees that every cab in existence does). In particular, I have no idea about EU-distributed Dancing Stage/EuroMIX/EM2 cabinets.
I) Python 2 unit:
The Python 2 unit is the main part for SuperNOVA and SuperNOVA 2.
Lol, it's literally a PS2-in-a-box:
II) Extended I/O unit:
Konami Part number: GKE33-PWB

This converts the lights and pad I/O into the serial format needed for Python 2-based DDR. Without this, the game will throw an I/O error and refuse to boot into game mode (have fun with the service menu if you like, though). Hardware-wise, it looks to be quite simplistic (2 ICs and a bunch of other smaller components), so it's probably possible to reverse engineer it quite easily if someone has the time.
SOURCING THE EXT I/O UNIT
Sadly, the only way to get this at the moment is through Konami's distributors (Betson in the US, Electrocoin in EU), and it's not cheap. The list price in the US is $585, and in the UK/EU it is £659+VAT.
Betson have proved to be a bit flaky with regards to communications - they've outright refused to sell to someone in the US in the past on the grounds that he didn't have a valid US serial number (since he was using a Japanese SuperNOVA 2 main board), and it took me 8 months (and several unanswered emails) to finally get in touch with someone at Betson who actually was competent at his job and replied to emails!
III) Cabling:
There's a bunch of cables required to get this all up and running. The official Konami part numbers are:
[*]GKFDHUA00012 - Neon -> Ext-I/O PCB
[*]GKFDHUA00010 - 1P Lamp -> Ext-I/O PCB
[*]GKFDHUA00011 - 2P Lamp -> Ext-I/O PCB
[*]GKFDHUA00014 - 12V power
[*]GKFDHUA00003 - SCI -> Ext-I/O PCB)
[*]GKFDHUA00013 - Ext-I/O in -> Ext-I/O PCB
[*]GKFDHUA00004 - Lamp PCB -> Python 2 motherboard
...Unless you like soldering cables yourself, you might also like to get a quote for a replacement SN JAMMA loom and these two power cables:
[*] GKFDHUA00007 - JAMMA Loom
[*] GKFDHUA00005 - MC_PWR and 12V power cables
...And if you want to be a completist:
[*] GKFDHUA00061 and GKFDHUA00062 - 120V-100V Transformer and cable
My local distributor wanted GBP£395+taxes for these, so I made my own.
MAKING YOUR OWN CABLES
If you are rolling your own, you'll need to make the following cables:
1) EXTIO power (12V) [Connector: VHR-3N to your DC power supply]
2) Python 2 power (100V) [Connector: VLP-03V, other end to your AC power supply]
3) 1P lights -> EXTIO [Connectors: XMR-10V to XHP-10]
4) 2P lights -> EXTIO [Connectors: XMR-10V to XHP-12]
5) Bass Neon -> EXTIO [Connectors: XMR-06V to XHP-6]
6) Python 2 -> EXTIO [Connectors: EHR-5 to XHP-3]
7) EXTIO -> Jamma loom [Connector: XHP-5, other end soldered onto the JAMMA loom]
8) Cab lights -> Python 2 [Connectors: XMR-10V to XMP-11V]
9) (OPTIONAL and not needed) Python 2 MC_PWR (5V) [Connector: VHR-4N, other end to your DC power supply]
You'll need the following JST edge connectors:
3 x XMR-10V : Socket for 1P,2P and cab lights from cabinet (I scavenged these from a broken System 573 to save effort)
1 x XMR-06V : Socket for Neon from cabinet (I scavenged these from a broken System 573 to save effort)
1 x VHR-3N : +12V Power for Ext I/O
1 x XHP-3 : Ext I/O to P2 COM1, Ext I/O end
1 x XHP-5 : From JAMMA to Ext I/O
1 x XHP-6 : Neon connector to Ext I/O
1 x XHP-10 : Ext I/O 1P Lights
1 x XHP-12 : Ext I/O 2P Lights
1 x EHR-5 : Ext I/O to P2 COM1, Python 2 end
1 x XMP-11V : To Python 2 (Lamp)
1 x VLP-03V : Python 2 100V power
1 x VHR-4N : MC_PWR +5V (NOT NEEDED, BUT ON THE SCHEMATICS)
You'll need a bunch of pins for these connectors, too:
3 x SEH-001T-P0.6 : EHR contacts
23 x SXA-001T-P0.6: XMR contacts
8 x SXM-001T-P0.6 : XMP contacts
24 x SXH-001T-P0.6 : XHP contacts
4 x SVH-21T-P1.1 : VHR contacts
2 x SVF-42T-P2.0 : VLP contacts
The XMR-connectors I scavenged off a broken System 573 board to save time and effort - they are simply the 4 lights sockets on a 573 motherboard, and can be entirely detatched from the Analogue or Digital I/O board, and then popped out from the face plate.
1) EXTIO power:

Trivial: Pin 1 goes to a +12V source (e.g. JAMMA pin 6 or from your cab's DC power supply), and pin 2 to ground (e.g. JAMMA pin 1)
2) Python 2 power:
Wire pin 1 and pin 2 into an AC 100V supply. The Python 2 unit does not use or require an earth wire. From a functional point of view, it doesn't matter which way round you do this (strictly speaking pin 1 should be AC neutral and pin 2 AC live/hot, but since it's a PS2 in a plastic case inside a sealed unit, it shouldn't be a safety issue if you get it the wrong way round, though as a general principal you should get this the right way round on mains AC stuff).
3) 1P lights -> EXTIO
4) 2P lights -> EXTIO
5) Bass Neon -> EXTIO

These are all straight pin-to-pin wirings. The 1P connector (white) goes to the 10-pin XHP housing, the 2P connector (orange) goes to the 12-pin one. The bass neon is the 6-pin white connector.
When finished they'll look like this (2P only shown):
6) Python 2 -> EXTIO [Connectors: EHR-5 to XHP-3]

This is a serial data crossover cable. If you get this wrong, SuperNOVA will give an error when booting and drop out into the operator menu.
Wiring:
EHR pin 1 to XHP pin 2
EHR pin 2 to XHP pin 1
EHR pin 5 to XHP pin 3
7) EXTIO -> Jamma loom [Connector: XHP-5, other end soldered onto the JAMMA loom]

Wiring:
Pin 1 soldered onto JAMMA 1P UP (pin 18)
Pin 2 soldered onto JAMMA 1P RIGHT (pin 21)
Pin 3 soldered onto JAMMA 2P UP (pin V)
Pin 4 soldered onto JAMMA 2P RIGHT (pin Y)
Pin 5 soldered onto JAMMA ground (e.g. pin 1)
8) Cab lights -> Python 2 [Connectors: XMR-10V to XMP-11V]

Wiring:
XMR Pin 1 to XMP pins 1 and 6 (grounds)
XMR Pin 4 to XMP pin 2
XMR Pin 5 to XMP pin 3
XMR Pin 6 to XMP pin 7
XMR Pin 7 to XMP pin 8
XMR Pin 8 to XMP pin 9
XMR Pin 9 to XMP pin 10
XMR Pin 10 (earth) not required.
When finished it'll look like this:
9) (OPTIONAL and not needed) Python 2 MC_PWR (5V)
As with cable #1, this is trivial. Pin 1 goes to +5V (e.g. JAMMA pin 3 or from your cab's DC power supply), pin 2 to ground (e.g. JAMMA pin 1). It's also not needed - this is used to power the memory card sub-board on the Python 2, which ultimately was not used in SuperNOVA/SN2.
When it's all finished and cabled up, it sohuld look a bit like this:
On a Korean cab, there's space to store the old System 573 unit on top of the Python 2 unit for quick changes (you might not be able to do this with a Japanese cab as they store the units vertically instead of horizontally):
Appendix A) Schematics:
Annotated SuperNOVA schematics (showing the differences from ye olde cabs) can be found here:
http://www.flickr.com/photos/chi-ryu/tags/snvsoldddr/"
Appendix B) JAMMA Pinouts
A breakdown of the JAMMA pinouts can be found e.g. here:
http://www.coin.demon.co.uk/jamma.htm"
[1] Often these units are seen with two security plugs (one black one white) - you only need the black one. The white one is a hardware identifier plug - used to identify the machine on e-Amusement, amongst other things.
[2] Usually there is an internal 120VAC source for cabinets used outside of Japan, but it doesn't really make a difference in practical terms. If you want to be a completest, get a 120V-100V stepdown for the Python 2 (you can find them in airports in Japan, or mail ordered for silly money), but I didn't bother. If you are happy enough to run a Japanese Playstation 2 from US mains/120V stepdown, this is literally no different.