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Mordaunt Short 409w Sub repair worked!!

Discussion in 'Subwoofers' started by pinguS, Dec 31, 2009.

  1. pinguS

    pinguS Member

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    I am new to this forum stuff, but I have sorted my problem out on my Mordaunt short 409w Sub woofer.

    Problem status was no sound but:
    1. Green light on
    2. Neon front blue light on
    3. In auto sub comes out of standby and turns green light on, but still no sound.

    After a bit of messing around, soldiering 1 wire, although I could have just used a junction block, mines been working of for a month now, in all 3 states, off / auto / on.

    If anyone still interested and you haven't thrown it in front of a train, then just reply, saves me having to write down the solution which worked on mine if no one cares.

    note: as mine is now screwed back together, for the solution I would need someone to post the pictures of the boards on this post for me to indictate what I soldiered together, even though you could just strip wires and use a junction block.

    ...... thats enough waffling for now...oh and I may not reply until the 4th now even if someone posts as hey its the new years eve..... time to get drunk......
    Last edited: Dec 31, 2009
  2. roncam29

    roncam29 Member

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    Hi I have one off these it has started playing up, sometimes it comes on and other times it is silent so I play about with the cable and it seems to work for a while then stops working again, so I would be interested in how you fixed yours.
  3. adriandg

    adriandg Member

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    My 309w did exactly the same thing a month or so ago. So any guidance on how to fix it would be most appreciated.

    Cheers
  4. pinguS

    pinguS Member

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    Ok
    To fix this I would need a picture of the inside with the boards, this is so I can edit the picture in photoshop and show what I did. You do need to join a red live 240v wire with another wire, but I can't remember the colour. Also my one is a 409w, so any other sub may NOT be the same.

    What I had to do was remove the black rubber from the covered PCB and soldier a wire between the red and another wire. But you don't actually need to remove the black rubber stuff if someone can post a picture.

    Note: this worked on mine, but there is no guarantee for anyone elses, if you now how to use a micrometer, then removing the rubber stuff, would make it easier to see if what I did would work. Or you could just go hell with it and join the 2 wires regardless (which should not be a problem, but for piece of mind)...
  5. roncam29

    roncam29 Member

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    Thanks for your reply but I have bitten the bullet and bought a monitor audio rsw12 subwoofer, when I get it I will take a couple off pictures off the modules in the MS sub and post them and maybe I will be able to fix it with your help, if not I'll just throw it in front off a train, I have had it for nearly 6 years and by some off the threads on here I have been lucky it has lasted so long.
  6. pinguS

    pinguS Member

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    Cool

    But if you do get a chance to open it, the wires I joined or soldiered together were I believe a red one which goes into the rubber covered PCB unit to a yellow one (need picture to confirm) coming out of the rubber PCB unit. i.e. just join them at the PCB end with solidiering a wire between the 2. Or put a junction block in to link the red and yellow on the PCB unit side to the red and yellow to the big round unit side.

    For explaination, I found that when turning the power on, the white ribbon wire was powering up only the 1st stage, so the neon turned on but something like a diode / capacitor was not opening up on the rubber covered PCB to allow 240v power to pass through to the yellow wire leading to the big round thing.

    I just bipassed this stage giving instant 240v power to the yellow wire from the red wire. Maybe Mordaunt Short could have done this and save themselves a PCB unit.

    Obviously some sort of electronic genius by Mordaunt Short to give safety of sound to the main PCB, but hey this worked for me and has been without any problems, and exactly as if new.

    Please be careful if trying this as only you are responsible for your own safety etc....
  7. plumbob

    plumbob Member

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    Anyone had a intermitent booming noise from a Mordant 409 sub woofer.
    It does it even when it is not connected to anything.
    There will be silence then a rumbling noise and then quite lound booms and pops.
    I have moved it away from the tv, electrical sockets etc with no effect it still does it.
    It was part of a set of Genies and they have been great, i just hope you guys can help to save spending on a replacement.
    Thanks.
  8. pinguS

    pinguS Member

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    Sounds like you have something in the line in connector, either stuck or something, I may be wrong....
  9. Duckeymoon

    Duckeymoon Member

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    Hi, I am having the same problem with my 409w and I was inspired by your success so I thought I would give it a go. Unfortunately I fell at the first hurdle as I can't seem to get the back panel off. I have undone all the screws and taken the knobs off including there nuts but the panel still seems as fixed on as before. Am I missing something or is there a technique to it?

    Any tips would be much appreciated.
  10. pinguS

    pinguS Member

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    You do not need to remove any knobs. The only screws you should undo are all the outside ones, around 10 from what I remember and the 4 larger ones closest to the corners.

    It is a bit of a struggly, but I found out by just sticking a knife in the side and sort of forcing it loose. ( this is an excellent fit Mordaunt Short have achieved.)

    It will pop out, just try a little harder, but you do NOT need to remove any of the other screws, as a warning they keep the electrics on the inside attached)
  11. Duckeymoon

    Duckeymoon Member

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    Hi, thanks for your tips on removing the panel I have successfully got it off. Did you manage to get it to come out all the way or did you just work within this gap? I can only get it out 3 inches or so. If I turn it upside down I can see a pcb covered in black plastic, do I need to take the plastic off to reveal the wires you mention?

    Many thanks for your help.
  12. pinguS

    pinguS Member

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    You do need to get the whole thing out to make life easier. It only comes out 3 inches because the wire going to the actual speaker has been glued with some black resin to the black plastic box thing.

    If you can get your hand behind the black plastic box thing, you can unwrap some foam stuff around the wire to reveal a clip for the wires and unclick, or if you can get upto the actual speaker, just pull off the wires from the speaker (problem with this is you do not know where the red or black wire goes, so use a torch first).
    What I did was to just cut the black resin off the back of the black box to allow the wire going to the speaker to move freely.

    Regarding the PCB, I did take off the black rubber stuff, by cutting with a stanley knife to one side and just take it off to make it easy to put back on once finished.

    If you get this far, then post to let me know how your getting on, I have explained the soldier points, but post a picture of the PCB unit (both sides) and I'll just draw on there where I joined.
  13. Duckeymoon

    Duckeymoon Member

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    Hi pinguS,

    Thanks again for the extra instructions, I have finally got the board out :thumbsup: I have attached a picture of the pcb which I hope is detailed enough for you to modify in Paintshop. I will probably go for the junction block approach. For your information the wires coming from the power outlet to the board are the red and brown ones.

    Thanks again for all your help, it does seem a bit weird that you can bypass an entire board and it still works. :)

    Attached Files:

  14. pinguS

    pinguS Member

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    I have updated the picture, notes:

    1. This is for when you get the green light on the back and neon on the front, (you probably unpluged the neon light when you took out the electrical unit)

    2. If you look at the bottom end of the picture, I find this to be the easier approach,I just soldiered the 2 points together, red and yellow, on the bottom of the PCB unit (just get an old appliance mains lead and cut some wire out, be careful though as soldiering does get f+-k*ng hot)

    3. The junction block approach you have to cut and strip both wires (yellow and red) so that both get linked together, i.e. the yellow and red on the PCB end connect to the red and yellow on the other end) I hope the picture is clear enough.

    4. Be bloody careful, i'm guessing they have used rubber protection as the voltage is high on this PCB unit. To check my solution works, heres what I did.... Connect up the sub to the mains, attach a lead to the Line In, you can use your one from your system. The trick is to just use black tape temporarily to hold the wire down at the soldier points (look at picture). For the test, power up the unit. When on, touch the other end of the lead connected to the Line In with your thumb, you should start hearing a thuding noise. This indicated it has worked... If not just check the wiring has been held ok with the black tape and the volume is up. Oh yes also make sure the 2 fuses on one of the PCB have not blown and you are still getting the green light on the sub back end when switched on.

    Hope this is enough to get you through another evening... and if it works, make sure you put the rubber stuff back over the pcb and just wrap it with black tape, safety first....

    Attached Files:

    Last edited: Jan 22, 2010
  15. Duckeymoon

    Duckeymoon Member

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    Thanks for the picture and instructions. I gave it a go last night using black tape but no sound came out. The light was on and I checked the fuses and volume. I will give it one more go by soldering just in case the taped connections aren't making proper contact. I'll keep you posted.

    Cheers
  16. Duckeymoon

    Duckeymoon Member

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    Hi pinguS
    I have decided to take the junction block approach but I am a bit confused as to what should be connected to what. You mention that the red and yellow wires at the pcb end should be connected together and also the red and yellow from the other end should be connected together. I notice that the red wire from the other end is not connected to the pcb red wire but to an orange wire so it is different to how the yellow wire is connected. I was wondering why I could not just cut the red wire coming from the power outlet and cut the yellow wire coming from the big round thing and connect those two together taking out the pcb altogether, is that not the equivalent of the soldering solution or is the pcb still needed for something?

    If I do need to connect all four are they all connected to each other inside the junction block?

    Sorry to be a pain, many thanks again for your help.
  17. pinguS

    pinguS Member

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    The way my soldiering worked makes all 4 wires connected to each other. The PCB is still used, this is to power up the sub initially, but on my one that is all it did, not follow the power up on to allow the sound elements to work.

    So in theory you DO need to junction block up all four so they are linked, I am not sure where your seeing an orange wire, is this at the ball shape thing end. I didn't even touch this wire.

    I can't see why you were not able to try the unit by touching a wire to the solier points held with black tape and then powering up the sub, did you re connect the speaker wires internally to the sub's actual speaker. (I know this sounds simple, but I wasted about 30 minutes because I didn't do this). Also did you touch the line in connection with your thumb. Have you tested the fuses with a tester to make sure they are not blown, these fuses sometimes look ok, but are blown under one end which you cannot see. (testing to see if a beeping sound comes out of a tester to check continuity)

    When I did my check, which I DO NOT RECOMMEND!!!, I actually:-
    1. Powered up the sub without the soldier point test / connected
    2. Got a wire / paper clip, held with a rubber handled pliers.

    3. Then I held the line in wire in one hand and using the pliers touched the soldier points with the wire. When touching the soldier points, I just kept putting my thumb on the line in wire to check if a thudding sound comes out.
    • Thanks Thanks x 1
  18. roaduck

    roaduck Member

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    First of all well done pinguS fixing your Mordaunt Short 409.

    I had a MS-309 which was fantastic value for money being powerful and fast if not that deep at 35 HZ which is higher than my main 3-way dipoles but if I thrashed the sub the protection circuit came on and they cut out especially when the voice coil got hot and the whole woofer was warm - I could smell hot melted glue!

    I flogged the MS for a song - £50 and got a big lad - A BK Monolth custom with the 500 watt amp and better Eminence 12" woofer - it is sensational - a normal sub looks like a satellite next to it - it sounds like a very expensive REL but with more power - It has more slam and less distortion than a Quake and it is a total bargain at less than £570 delivered with superspikes.The Volt woofers are good because I have them in my SD Acoustics OBS 3-way dipoles but they're only 100-150 watt woofers and they would not like 500 watts of quality AB through them.
    Last edited: Jan 27, 2010
  19. Duckeymoon

    Duckeymoon Member

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    Well unfortunately my second attempt using a block failed as well. I am ready to throw it in front of a train now. Reading other forums it sounds like loads of other people have had problems with this sub. I have bitten the bullet and ordered a BK Gemini II as a replacement.

    Thanks pinguS for all your help and advice.
  20. neilw1

    neilw1 Member

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    Hello, when I click on the image links in this thread it tells me I don't have permission?

    I know it's an old thread.

    [edit]Actually, google search shows me the image....
    Last edited: Sep 18, 2012
  21. Frank1471

    Frank1471 Member

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    You really need to be aware of what you are doing with this proposal.
    In carrying out this, you are bypassing the relay contacts which switch mains to the power transformer. This will remove the auto switch-on function and cause the amp to remain powered constantly.
    It seems like this fault is quite common but it is not the only fault that causes this effect. As there is no technical information for the 309 and 409 models, it makes a "proper fix" virtually impossible.

    My measurements of the performance of the 409W show that it hasn't got the bass response commensurate with its size.
    My best advice would be to use this as an excuse to upgrade to something better.
    Frank
  22. SparkUK1

    SparkUK1 Member

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    It does look that way, the relay itself might be a good target for me to look at on mine but I'd agree about being wary or at least aware of the risks bypassing it.
  23. SparkUK1

    SparkUK1 Member

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    Well the relay was the right target, I've fixed mine rather than bodge it, if you take the toroid off and move it as far over as you can package wise you can fit a din socket on the plate and hard wire a 30a relay in properly. Works perfectly and cost less than a tenner. Bear in mind I sent this away to get looked at and got quoted just shy of £500 to repair for a replacement plate. That irritates me as I thought someone technical was going to look at it on a component level and it's quite some time since I've done any work of this nature.
  24. Pauli363

    Pauli363 Member

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    I have a Mordaunt Short 309 sub, which from what I can gather is pretty much the same unit as a 409. I have suffered for 6 months, with the sub only very intermittently working, but rarely. I was sure it was a relay problem, but was not sure how to isolate it. On reading through this thread, I decided to try Pingus' workaround and I can confirm it worked 100% for me. Unlike what Frank says above, it also leaves the auto power working.

    On stripping the amp down, it became apparent that the blue relay on the small board to the left in the picture below was the culprit.

    The relay is made by bluesky. Blue Sky Hosting - Managed Hosting, Office 365, Cloud Hosting, Lotus Domino When I powered the unit up after stripping from the cabinet, there was no signal to the speaker until I gently tapped the relay with a screwdriver. It would work for a few seconds then click off again. Another tap, and I would get power for a few seconds, then off again.

    However, I have not been able to source a replacement online as yet.

    [​IMG]
    [​IMG]


    So I decided to have a go at Pingus' workaround. I had all but resigned myself to purchasing a new sub, which I was not happy about, as the 309 serves my purpose well. It really is a decent little sub that was very well reviewed.

    On the 309, the yellow wire is switched with the black wire. So for the 309 plate amp, its the BLACK and RED to be connected, whilst on PINGUS' 409 board, it is the YELLOW to the RED that is connected.

    It will be clearer from the pics below.

    [​IMG]

    Notice the black wire in place of the yellow wire from pingus' photos earlier.

    [​IMG]


    so, I got a small 1 inch piece of copper wire bent in a U shape, and soldered to the black and red wire.
    [​IMG]

    on completion, I had full power restored. Nothing acting strangely, just the sub working as it always did before crapping itself.

    Just remember. ANY MODS OR ADJUSTMENTS YOU MAKE ARE ENTIRELY AT YOUR OWN RISK! THIS WORKED FOR ME, BUT IT MAY NOT WORK FOR YOU.
    ALSO REMEMBER, THE PHOTOS ABOVE ARE FOR THE 309'S BOARD, ON THE 409, IT IS THE RED AND YELLOW THAT ARE CONNECTED TOGETHER.
  25. Frank1471

    Frank1471 Member

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    No it doesn't.
    The amp will stay powered permanently. You have shorted the relay contacts which supply power to the main transformer.
    No big deal but you need to realise this and preferably remove the mains when not in use.

    Frank

    Replacement relay:
    Last edited: May 24, 2013
  26. Pauli363

    Pauli363 Member

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    Frank. If I kill the power switch at the back, the power light goes from Green to Red and the sound from the sub stops. The auto off for quiet passages still kicks in when the switch is set to auto, and powers the sub up again when a louder segment kicks in. In otherwords, exactly as was before.

    In any event, I don't leave power on with the av equipment when not being used. Everything terminates in a remote control power socket, and I switch the power off here when not in use.
  27. Frank1471

    Frank1471 Member

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    But you have removed the sub's ability to remove power from the majority of the electronics and achieve automatic power saving.
    The sub's "logic" still thinks its powering off and may indeed mute the output.

    Frank
  28. Pauli363

    Pauli363 Member

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    Mmmm. Fair enough.
    When I get the time, I'll try and source a replacement relay, as fitting it would be easy enough. In the meantime, this is a good workaround. I power off everything after every viewing anyway, so there shouldn't be any issues
  29. Steven1210

    Steven1210 Member

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    Look at Franks post, think he found the relay for you. I had same issue with mine, then one day, POP, cap blew.

    Steve
  30. Frank1471

    Frank1471 Member

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    If you need a relay, I have one here and can maybe save you the minimum order charge etc. I can add a replacement to my next order.
    PM if interested.
    Frank

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