Analogue-sequencer

> The 'R2' resistor on the mainboard should have a 510R. But I couldn't
> find one in the standard 0.6W range. Instead I've found this one of
> 0.5W (Farnell order code 544-528). I guess that's ok ?

That would be fine.
Or you could use a slightly different value.
470R should work fine, as would 560R, if you can get those.
I used to use 1k, which worked OK with many 6N139s, but not all, which was
why I switched to 510R.
The lower value pull-up resistor ensures a nice sharp rising edge.

Best regards,
Colin Fraser
Sequentix Music Systems Ltd
http://www.sequentix.com