Schematic diagram for Mordaunt-Short MS309-W

OXAUDIO · 12th January 2012, 10:43 AM

Can anyone supply, or tell me where I can get, a schematic diagram or Service manual for the above, please. A U.K. source for spares would also be helpful.
The 1.6AT fuse in the mains input blows in one I'm trying to repair, and none of the usual suspects(Rectifier, Filter Capacitors, etc.,)are faulty. Prior to the fuse blowing, the amp. would cut out if the volume was advanced more than about 60%, with only a 'signal' from my finger on the line level i/p present
Could the mains transformer have shorted turns??

jaycee · 12th January 2012, 12:00 PM

More likely output transistors failed. The back of the sub mentions "digital" so its possibly a class D amp.

OXAUDIO · 12th January 2012, 06:17 PM

Didn't think of that possibility, jaycee. Thanks for the tip. I'll check them ASAP. The O/P
Transistors are mounted on a Heatsink/PCB assembly attached to the main board so not too difficult to get to. Not sure what type they are, though. Hope they're easily sourced.

12th January 2012, 10:43 AM	#1
OXAUDIO diyAudio Member Join Date: Sep 2006	Schematic diagram for Mordaunt-Short MS309-W Can anyone supply, or tell me where I can get, a schematic diagram or Service manual for the above, please. A U.K. source for spares would also be helpful. The 1.6AT fuse in the mains input blows in one I'm trying to repair, and none of the usual suspects(Rectifier, Filter Capacitors, etc.,)are faulty. Prior to the fuse blowing, the amp. would cut out if the volume was advanced more than about 60%, with only a 'signal' from my finger on the line level i/p present Could the mains transformer have shorted turns??

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12th January 2012, 12:00 PM	#2
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	More likely output transistors failed. The back of the sub mentions "digital" so its possibly a class D amp.

12th January 2012, 06:17 PM	#3
OXAUDIO diyAudio Member Join Date: Sep 2006	Didn't think of that possibility, jaycee. Thanks for the tip. I'll check them ASAP. The O/P Transistors are mounted on a Heatsink/PCB assembly attached to the main board so not too difficult to get to. Not sure what type they are, though. Hope they're easily sourced.

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