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Sunil Sharpe revealed to me this week (on the 3rd of the 3rd - aka 303 day) he once owned a Roland MC303. After i stopped laughing, i got to the questioning about what it did well & badly.. From what i remember, it was a cash-in from the late 90's, branded a GROOVEBOX.. Basically, it was a rompler, loaded with harmonic partial samples (as seen in the K2000 series & the Quasimidi dance range) and pcm waveforms and full samples, prepared on the Roland S7x0 series, aimed at 'dj producers'. The annoying thing was it wasn't a 'workstation' with a good control surface as such, but more like a bunch of preset 'grooves' - ie: pre-prepared sequence loops you could apply to the banks of sounds. It was 8-part multi-timbral, kind of, and had 20-somethng voices. or something. it was soon joined in the range by the mc505, which added some stuff, but kept the same fenced-in idea lit.
So, prompted by our chat, Sunil dug out his mc303 from the garage it had sat in for a decade, and we got to work modding it after using some foam-cleaner on it to remove the cat-piss, and building a power supply for it - it's non-standard, with + 9 to +12v on the RING of the power jack. nice one roland.
The first thing You need is the diagram in the Roland mc303 service manual I found a copy here but it is all over the place, so go ahead and grab it, and get the back panel off your mc303.
You can see that there are some lovely socketed eproms to the left, these are on a daughterboard for later models - these are NOT FOR BENDING, as they contain all the useless patterns and grooves and the live OS. Bend these and you will lock up the machine.
I spent a fair whack of time trying to scramble the contents to make random patterns - not going to happen without building a harness and a diode matrix.
You need to head for IC 3 to the right as you look from the front & underside of the device. It's a small looking innocent chip, 44 pins, and is the sound rom. We need to attack the address lines. You can see from the diagram there are a shitload of these, but due to the nature of the package, the results are not as pleasing as you would expect. The good news is, the rom is quite robust, and you can cross bend and short almost any of the A-lines with each other with a fast return to normality when you stop. So, Pins 2 thru' 11, and 34 thru' 44 are all game for a poke.
These are the bends i hard wired into Sunil's unit:
44 - 10/11 (3-way toggle, 44 to 10, 44 to nothing and 44 to 11)
43 - 10/11 (see above)
4 - 5 (simple switch)
44 - 42/43 (see above)
32 - 44/43/36/34/33 (3-way toggle & 3-way rotary switch giving 1 x 6 routing)
If You look at IC3 you can see some legs have copper pads next to them on the board. These are of limited use, as they lead to pins we want to avoid, but they help. You have to face up to the fact you will have to solder onto the legs of the chip directly. this is hard work. the method i use was to melt a small blob of solder onto the nib of my soldering iron, then i slowly tap this onto the pin i want and the solder flows onto it, making it appear 'thicker' to the eye. then i tin the wire with solder, press it in place against the leg, or tape it down with masking tape in place, and then heat both - when it flows they are joined and i pull away blowing cold air on the area. You need to be very steady and quick. too much heat and you will lift the IC from the board, too much solder and you will short legs together.
Look half-way up the left side of IC3 - there are 2 pins in the middle that are shorted to ground - these are good pins to use to short any of the address lines to, should you feel nervous about shorting address lines to other address lines. Just sayin.
So, thats it. nothing too crazy, just another rom bend. The results are less impressive then with 8-bit PCM, more distortion then you would find useful for music, but there are some lovely address-shifting scrambles to be had that are excellent - you can make the drum sounds warp into harmonics which is great etc.
All the fx and filters and so on work still - remember you are only scrambling the address table with the bends, so you can still rely on the general function of the device.
Given the mc303 is a pile of crap, and changing hands for 100euro now, this is a great shortcut to circuit bending minerva.
For the future: I would like to put IC3 in a harness and instead of shorting and crossing lines, SWAP them. so swap 4 & 5, instead of shorting them if you get me. i think in the 16-bit (compressed?) world the mc303 lives in, this will yield more interesting results then the usual method that delivers so well with 8-bit roms.
So, prompted by our chat, Sunil dug out his mc303 from the garage it had sat in for a decade, and we got to work modding it after using some foam-cleaner on it to remove the cat-piss, and building a power supply for it - it's non-standard, with + 9 to +12v on the RING of the power jack. nice one roland.
The first thing You need is the diagram in the Roland mc303 service manual I found a copy here but it is all over the place, so go ahead and grab it, and get the back panel off your mc303.
You can see that there are some lovely socketed eproms to the left, these are on a daughterboard for later models - these are NOT FOR BENDING, as they contain all the useless patterns and grooves and the live OS. Bend these and you will lock up the machine.
I spent a fair whack of time trying to scramble the contents to make random patterns - not going to happen without building a harness and a diode matrix.
You need to head for IC 3 to the right as you look from the front & underside of the device. It's a small looking innocent chip, 44 pins, and is the sound rom. We need to attack the address lines. You can see from the diagram there are a shitload of these, but due to the nature of the package, the results are not as pleasing as you would expect. The good news is, the rom is quite robust, and you can cross bend and short almost any of the A-lines with each other with a fast return to normality when you stop. So, Pins 2 thru' 11, and 34 thru' 44 are all game for a poke.
These are the bends i hard wired into Sunil's unit:
44 - 10/11 (3-way toggle, 44 to 10, 44 to nothing and 44 to 11)
43 - 10/11 (see above)
4 - 5 (simple switch)
44 - 42/43 (see above)
32 - 44/43/36/34/33 (3-way toggle & 3-way rotary switch giving 1 x 6 routing)
If You look at IC3 you can see some legs have copper pads next to them on the board. These are of limited use, as they lead to pins we want to avoid, but they help. You have to face up to the fact you will have to solder onto the legs of the chip directly. this is hard work. the method i use was to melt a small blob of solder onto the nib of my soldering iron, then i slowly tap this onto the pin i want and the solder flows onto it, making it appear 'thicker' to the eye. then i tin the wire with solder, press it in place against the leg, or tape it down with masking tape in place, and then heat both - when it flows they are joined and i pull away blowing cold air on the area. You need to be very steady and quick. too much heat and you will lift the IC from the board, too much solder and you will short legs together.
Look half-way up the left side of IC3 - there are 2 pins in the middle that are shorted to ground - these are good pins to use to short any of the address lines to, should you feel nervous about shorting address lines to other address lines. Just sayin.
So, thats it. nothing too crazy, just another rom bend. The results are less impressive then with 8-bit PCM, more distortion then you would find useful for music, but there are some lovely address-shifting scrambles to be had that are excellent - you can make the drum sounds warp into harmonics which is great etc.
All the fx and filters and so on work still - remember you are only scrambling the address table with the bends, so you can still rely on the general function of the device.
Given the mc303 is a pile of crap, and changing hands for 100euro now, this is a great shortcut to circuit bending minerva.
For the future: I would like to put IC3 in a harness and instead of shorting and crossing lines, SWAP them. so swap 4 & 5, instead of shorting them if you get me. i think in the 16-bit (compressed?) world the mc303 lives in, this will yield more interesting results then the usual method that delivers so well with 8-bit roms.
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