ba662 tall clown

pile of clowns

Here are the Gerber files for my version of the Open Music Labs BA662 replica.

ba662-tall-clown-rev-b.zip

I’ve called it the tall clown ‘cos it uses BCM847DS and BCM857DS dual transistors, rather than the tiny PMP4201/5201 in the OML version. It’s a bit easier to hand-solder than the OML original, but not much.

I’ve tested these in my System 100M clone and they seem to work, but ymmv.

The filenames follow the iTead naming convention, and the board size is 22.0 x 12.1 mm.

If you prefer, here’s a link to the (untested) project on Oshpark – three boards will cost $2.05.

clown full frontal

Thanks to Open Music Labs for doing all the hard work on reverse engineering the circuit. This particular layout is my fault, so blame me for that.

Here’s a handy map of where things go – it’s from rev A, but the components haven’t changed position. The resistors are both 0805 sized.

ba662 tall clown map

If you can’t be arsed with soldering such tiny components, the OML versions are distributed through Synthcube, try them instead.

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System 100 VCF mystery solved

Alright, not much of a mystery, but have been drawing up some new PCBs over Christmas and wanted to check something on the System 100 (not M) VCF – the original schematic specified a dual 100KA for the resonance potentiometer, but I always suspected it suited a reverse audio pot better.

Here’s a picture from my 102, with the panel flipped down in front of me (so top here is bottom of the panel, just to make it confusing)

System 100 VCF pot orientation

Check the orientation of the embossed numbers on the back of the pots, and compare the (upside down) resonance and HPF pots against the right-way up mixer section (RM, VCO and Ext.).

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Flashing lights of the 100M


Continuing with some stuff from my ongoing silly giant-sized clone 100M – here is the flashing lights bit from the VCA and VCF circuits in action.

It’s unlikely it’ll be of any use to anyone, ‘cos it uses a (possibly unregulated) 22V power line from the 100M PSU, but, just in case – here’s the layout:

Roland System 100M level indicator stripboard

The lights on the 100M are meant to be useful, telling you when signal is coming out of the output, and if you’re pushing the level too hard. In practice, the overdriving seems to kick in slightly before the red light comes on.

It’s lot of effort for some pretty lights, but the whole thing has been a ridiculous endeavour so far anyway; so in for a penny, in for a pound.

The 100M level detector works more reliably than I’ve so far managed with the System 700 equivalent, which seemed to need very specific transistors, and even then occasionally gets stuck.

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