Roland mc-202....................Help me!

squidfanny · March 14, 2008, 10:35:15 AM

Hi y'all. . . I nee some help regarding my awesome sounding roland mc-202' analogue synth, circa 1983.......

Baiscally I brought it 2nd hand from ebay, with the intention of doing some serious mods on it. The problem is, I open it up to find that there has already been a load of 'mystery' mods done on the machine. Strangest of all - there seems to be an EXTRA component bolted onto the board.
It is a shiney brown circuit board with a chip, and 7 wires which are patched onto the main mc-202 circuit board at various locations. The numbers on the chip read - OC4 4 / HD14015BP.

What the hell is this thing? If it's a midi retrofit, then where's the midi input socket? (I've tried the din-sync and there is no reaction from midi data). I would be really greatful if some one could take a look at the photo and explain to me what this mystery component is........... I really want to get modding on my mc-202, but I really need to make some sense of the previous mods first. Thanks you all very much,,,, photo links below -

http://img136.imageshack.us/img136/5686/whatisthisgn9.jpg

Signal:Noise · March 16, 2008, 01:26:46 PM

contact the previous owner, chances are he might know.

Circuitbenders · March 16, 2008, 09:16:30 PM

Has anyone else got an MC202 on this forum? It looks to me like that board is meant to be there, at least it seems to fit a little conviently if its not.

I'm told that one of the main problems with the MC202 is that incoming CV and Gate signals don't go straight to the synth circuitry, but instead are stored in the sequencer and then sent onto the synth giving a sluggish external CV response. There are a few mods out there on the net that solve this issue, the simplest being just injecting the external CV straigt into the synth circuit, but this could be one of those mods.

computer at sea · March 16, 2008, 09:51:55 PM

Along the same lines, does anyone happen to know if the TR-505 comes standard with 8 sub-mini outputs? The one that I bent had a small extra board devoted, as far as I could tell, to sending triggers from each drum voice, and the workmanship looked neither pro nor amateur.

Circuitbenders · March 16, 2008, 10:01:55 PM

Quote from: computer at sea on March 16, 2008, 09:51:55 PM
Along the same lines, does anyone happen to know if the TR-505 comes standard with 8 sub-mini outputs? The one that I bent had a small extra board devoted, as far as I could tell, to sending triggers from each drum voice, and the workmanship looked neither pro nor amateur.

That was never standard or even optional but i've heard that trigger outputs are a possible mod, unless that was a dream i had $:-\$

gmeredith · March 16, 2008, 11:46:35 PM

The chip is a dual 4-bit static shift register, if that helps. The datasheet is attached below.

P.S. You nearly spilt your coffee all over it, Squidfanny!!

Cheers, Graham

computer at sea · March 17, 2008, 01:19:56 AM

QuoteThat was never standard or even optional but i've heard that trigger outputs are a possible mod, unless that was a dream i had

They have a tutorial for it over at Burnkit's site. That and a zillion other nice mods.

squidfanny · March 19, 2008, 12:16:59 PM

Quote from: gmeredith on March 16, 2008, 11:46:35 PM
The chip is a dual 4-bit static shift register, if that helps. The datasheet is attached below.

P.S. You nearly spilt your coffee all over it, Squidfanny!!

Cheers, Graham

Thanks for your help man, do you have any idea what 'dual 4-bit static shift register' does? It sounds like a Borg component from the shield section of a space craft. . . . . . I reckon it might be a later revision on the original mc-202 design. It was a pretty major flaw regarding the sequencer delay when using the cv/gate inputs, so maybe the extra component fixes this???
I've been using '202 hack' software to sequence the unit, as the inbuilt sequencer is pretty much useless for everything other than random acid sounds (which is also good). I don't have any cv/gate technology to test it with yet, but I might get myself a 'novation bass station' with cv/gate outputs and test it. Anyone used the cv/gate outputs from the bass station?

Now I just need to figure out why the unit doesn't sound how it should. . I'm guessing that it has something to do with the various (not original design) components which are soldered to the reverse of the board! I can see about 8 resistors and 5 capacitors and a couple of places where the circuit track has been cut............ Looks like I'm gonna be a very busy bee for a couple of days

LOL spilt coffee......... you don't know how true that nearly was!