QSC MP-M40 Schematic request or part ID

[the3secondrule]

Hi all,

Attempting a repair of a QSC MP-M40 that's lost a couple of channels of Audio I/O, and need to identify Q56. Appears to be either an voltage reg or transistor/FET etc.
Unfortunately (per the attached photo) it's failed violently so the only markings I can make out are "LL". It's shorted on all pins, so I can't even try and determine a pinout.

I've identified a few other issues (mostly bulging electrolytic caps), but without an ID on Q56 I'm pretty stuck.

Anyone able to assist?

TIA

[tedmich]

Once registered with QSC they give you access to much of their tech documents. While I've done this and got plenty of docs online from them (Im nothing official!) there is no service repair or schematic listed for these music systems (that I can find).

If you register and enter a specific case inquiry you may be able to get the info you need, good luck!

[The Dude]

Is there perhaps a working channel with the same part that you can get the part number from?

[the3secondrule]

Is there perhaps a working channel with the same part that you can get the part number from?

Unfortunately, no. That was the first thing I'd checked.

[the3secondrule]

Once registered with QSC they give you access to much of their tech documents. While I've done this and got plenty of docs online from them (Im nothing official!) there is no service repair or schematic listed for these music systems (that I can find).

If you register and enter a specific case inquiry you may be able to get the info you need, good luck!

That's a good call - I'll give that go

[Jazz P Bass]

U48 appears to be a controller.
Q56: a mosfet.
A secondary power supply, maybe.

[the3secondrule]

Our best guess at this stage is that it's a voltage regulator for the USB board. Unfortunately it sounds like the unit received a power surge through the audio inputs, so I suspect there's significant damage through out.

[dmeek]

U48 is LT3757 so Q56 is probably a mosfet

LT3757-3757a.pdf