Mordaunt Short MS339 - No Power

Dem

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Hi all,

I just installed a new Marantz SR7015 AVR today and during setup realised there was no sound from the subwoofer. I checked the back of the MS339 and the power light was off. In fairness, I'd switched the power off to it at the mains socket a little while AGO, as didn't need it on while my Onkyo TX-NR616 AVR was playing up.

I've changed the plug fuse, then the power cord for a known working one, but still can't get it to power up. There's nothing obvious I can think of that would have caused it to die. Any thoughts on how I may be able to tease it back into life or at least anything I can check / reboot on it?

Thanks!
 
Have you checked inside the sub. Are there any fuses on the sub.
Didn't realise that there's actually a couple of glass fuses accessible at the socket where the mains lead plugs into the sub. As per attached pic, looks like one of those two T1AL250V fuses is blown! Ordered some replacements from Amazon, so fingers crossed that it's as simple as that to fix!
P_20210131_172001_1_1.jpg
 
Hopefully should be a cheap fix.

When you turn on the sub make, you should turn the avr on first before the sub, and when you turn the sub off, turn the sub off first before the AVR.

Good luck.
 
So, new fuses arrived and replaced in the rear of the subwoofer. Power LED comes on; excellent. However, sound from sub? None.... 🤣

So, I'm guessing that the reason for the blown fuse was something throwing a wobbly inside the sub, and whatever that is, is permanently bricked.

Ah well, was worth a go!
 
Sorry the new fuses didn't work. Don't give up just yet.

Are you able to check there is signal coming from the sub out on the amp?

Are there any burnt or loose wires or components inside the sub?
 
Sorry the new fuses didn't work. Don't give up just yet.

Are you able to check there is signal coming from the sub out on the amp?

Are there any burnt or loose wires or components inside the sub?
Thanks for the encouragement!

Well, I hoped it would be realitively straightforward to open up the sub, but despite removing all 10 torx head screws in the rear panel, it does want to come out. Already cut my hand on the heatsink... 🤣 Any thoughts? I don't want to butcher the housing by trying to lever it out in case I've missed something else that's holding it in? Surely not the speaker cone assembly itself?

Thanks!
16126244373632228539818281506516.jpg
 
Thanks for the encouragement!

Well, I hoped it would be realitively straightforward to open up the sub, but despite removing all 10 torx head screws in the rear panel, it does want to come out. Already cut my hand on the heatsink... 🤣 Any thoughts? I don't want to butcher the housing by trying to lever it out in case I've missed something else that's holding it in? Surely not the speaker cone assembly itself?

Thanks! View attachment 1455589
So, took the speaker cone out and used a long screwdriver to push the panel out from the opposite side....

Really nothing obviously blown or melted to me....
16126254206862122844180632803530.jpg
16126254206862122844180632803530.jpg
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16126255266344612664992644012663.jpg
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There doesn't appear to be anything visually blown. The only other thing I can think of is some loose wiring or something inside those black cases, sorry.
 
Sorry the new fuses didn't work. Don't give up just yet.

Are you able to check there is signal coming from the sub out on the amp?

Are there any burnt or loose wires or components inside the sub?
PS: ref signal, I used the sub from the cinema room to check and it worked with the new Marantz AVR in this room, so defo the sub.
 
There doesn't appear to be anything visually blown. The only other thing I can think of is some loose wiring or something inside those black cases, sorry.
Hey, no worries! It was worth a look!
 
After all that, I've
16126276134677243708824679189980.jpg
discovered what was wrong.... the "Auto Standby" was in the "Off" position. I assumed this was an additional function (so being 'Off' would not affect the basic use of the sub), but there is also a middle position for that switch as well as to the "On" position..... No idea how this got switched, but just happy I found it! 😂
 

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