Identification of SMD part, possibly a voltage regulator

[obiwanjacobi]

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.

[Microcheap]

I'm not sure, but I made a quick search at: http://www.smdcode.com/en/smd/code/search/?q=sc and got a result for a dc/dc convert from a japanese company called Torex
https://www.torexsemi.com/file/xc6371/XC6371-XC6372.pdf

Apparently this midi interface is made in japan, so it might make sense.

I hope this will be of some help.

[obiwanjacobi]

Thank you, that does look plausible.

However, in an attempt te reverse engineer the schematic from the PCB, I noticed that pin 3 (right most) on D20 is not connected.
It does not seem to go anywhere. I have tried to beep-out all nearby traces - nothing. It is not a via either.

So perhaps D20 is just a diode (to protect against reverse polarity)?

[PA0PBZ]

So perhaps D20 is just a diode (to protect against reverse polarity)?

I guess it is, and 5B points to a double diode. Just connect pins 1 and 3 and see if it works?

[JFJ]

The SMD (D20) part says: 'SC 5B'

As the pin 3 pad isn't connected to anything else, it may just be a low forward voltage diode, e.g:
http://www.mouser.com/ds/2/308/EN2985-D-462854.pdf

[obiwanjacobi]

Because I already desoldered the SMD device, I measured with the DMM (diode mode) between all pins in both polarities.
Non of the pins are connected at the moment, which leads me to conclude that indeed there is probably only a single diode in this package.
If it were a double diode, I would expect the other one to remain intact.

Thanks for all the suggestions.

EDIT: Yep, that worked 

[obiwanjacobi]

I got part of the schematic and it IS an SB20!