Help with finding obsolete Motorola 43121 transistor

I need to replace this transistor since it has tested bad...
I cannot find a single thing about it anywhere. It has the Motorola insignia and says 43121, then on the back it has 3 color bars, red, silver, and yellow.
Here is some pics of it and also in circuit.. (Q6 on schematic)

I couldn't find it using Google.

Please post the entire schematic.

How do you know it's bust, have you tersted it?

The chances are any small transistor will do.

Yes - I'm hoping someone can recommend a modern version...
Here are the somewhat cryptic schematics - it's a electronic musical instrument device...
Tested EBC as diodes- multimeter diode tester style..

It's a low current 35V odd regulator - what to use really depends what voltage is been fed to the collector.

I'd try a BC107 for a start, but any general purpose NPN will probably do.