I am repairing a Roland GI-10 Guitar MIDI Interface which does not turn on.
The unit is supplied with a 9V adapter and my guess is someone put in a too high a voltage.
I encountered a blown up C across the barrel socket input (which I removed) and the SMD part in question that did not output any voltage.
The SMD (D20) part says: 'SC 5B'
I first thought it would be a voltage regulator but the D20 designator does not make sense. A zener perhaps?
Possibly the other regulators (?) Q3, Q4 and Q5 are shot also.
Unfortunately I do not have a schematic.