[grawlinson]

> The optocoupler also works like a cheap (although somewhat hard to replace) fuse which is probably a good thing if you want to connect you Roland Jupiter-8 / Fairlight CMI to some dodgy equipment.

In this case, the older synths are more likely to have failing/dodgy components. I have a DX-7 that I'm going to have to replace a lot of components in, and this sort of knowledge/understanding really should be more common along synth enthusiasts.