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How to - Bose Subwoofer Cutout Fix (Amp)


cs2000

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Hey all, due to another members query about how they could fix their amp as the bose sub was cutting out, I did some digging and found the relay part you need to replace, below is a guide which will show you how to firstly remove the amp, and also the part you need to replace, along with two places you can currently buy a correct part.

 

Tools & Supplies Needed:

- Small flathead screwdriver

- 10mm socket wrench

- Soldering Iron

- Solder

- Replacement Relay (links are below)

- De-soldering Wick (Optional, but makes it much easier)

 

Step 0 (Purchase the relay):

The relay can be purchased from two locations in the UK. These are listed below.

Farnell (£1.74, but minimum order value of £20.00) - http://uk.farnell.com/multicomp/mccma51-s-dc12v-c/relay-spdt-12vdc-20a/dp/2008759

eBay (£3.73 with no minimum order quantity) - https://www.ebay.co.uk/itm/171118849805

In-case these links go down, the relay part number is "MULTICOMP - MCCMA51-S-DC12V-C - RELAY, SPDT, 12VDC, 20A "

 

 

Step 1 (Removing the subwoofer panel cover):

Starting at the top edge of the panel, behind the driver's seat, carefully pry away the top section using the flathead. Be careful not to scratch the plastic. It should come out pretty easily as its retained using clips. Remove & set aside.

 

551644399_5-noSjPx.jpeg.336053df2e2fb057022f116b3411685f.jpeg

 

 

 

Step 2 (Unmounting the subwoofer):

Remove the 4 screws holding the subwoofer in place using the 10mm socket wrench. Carefully lift out the speaker and set aside. There is no need to unclip the wiring harness, just be careful as it is a little short.

 

1193560015_6-6vad9r.jpeg.58b06e068fce63585a26fda242914251.jpeg

 

772084028_7-XM6YSJ.jpeg.aa9f3ec856890b981f327ad320115799.jpeg

 

Step 3 (Remove the subwoofer amp):

Loosen the 2 bolts holding the amp in place. Slide the amp up and out. Disconnect the wiring harness by inserting the flathead into the little groove on the harness. The amp should be loose now. Take this inside to do the electrical repair.

 

1551027965_8-ZVdhcv.jpeg.7ba7f42aef8d2df58da1bafd62199340.jpeg

 

Step 4 (Disassemble the subwoofer amp):

Crack open the amp's casing, it should be held together by 4 screws on its under-side. Once these are removed you should be able to lift and remove the metal amp housing from its plastic shell, don't worry yet about its connecting wires.

2099874171_10-QtD423.jpeg.4360eb45f9ce5a77a9434de9463ffcb6.jpeg

 

Next, again using the small screwdriver, lightly pry the metal lid from the rest of the metal case, a good place to start is the front retaining clip. as shown in the photo below, then do the sides and finally the lid should lever off. The lid is held down by a small seam of adhesive, so it will be tough. Release the PCB from its housing.

500721614_1-UHlrq3.jpeg.7d875a37211478ac91a0bdb903c2b3ed.jpeg

 

Next, use a small flat bladed screwdriver to lever the plastic wiring block away from the main board. I found this to be the easiest way to remove this.

1498551844_2-akaSup.jpeg.d1e8c5c86dd0907d94088ac6582fed7c.jpeg

 

Now you can see the offending component. Its this Relay on the right-hand side of the shown picture, yours will be a grey box about 1.5cm x 1.5cm

1354761374_3-Y5ZLLR.jpeg.3927b3b75f637f58c607e9c0d3987b9b.jpeg

 

 

Step 5 (Perform surgery on the amp):

From the picture above, flip the board over and use your soldering iron to remove the old relay, you have to de-solder the points shown in red below. I personally didn't have any desoldering wick, so I broke apart the old relay, heated up each solder blob and used pliers to pull out the last metal legs of the old relay. I then re-heated the solder and inserted a pin through it to make holes for my new relay.

1752085888_4-TDhoNH.jpeg.4ee05b2e7dd483f7d20b8ad510ea7a3f.jpeg

 

Get your fresh relay and ensure you insert it correctly into the holes left by the old one. Solder this all in securely and fit back into the car to test. And relax! Picture below shows new black relay installed.

106760213_9-UXLtdk.jpeg.8596202dc6c4ba85b9e8e6659aa2db44.jpeg

 

You can do a similar fix by just cramming paper/card in-between the relay and the amp's casing, but eventually, even this will fail & for people like me who actually like the Bose system (despite its many many issues) a permanent fix like this isn't bad for a total cost of a couple of quid!

 

If you really struggle, drop me a PM, I may be able to do this fix for you if you can post me your amp.

Edited by cs2000
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  • 1 month later...

Just opened up my amp to find this 😂

 

cardborad.jpg.841f5010cf08b65b4e29dd143d3aa3ae.jpg

 

 

I had big plans on bridging some cardboard in there but Somone beat me to it, guess I'll have to do it properly

 

 

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@Niko - Yes, the board usuall does look fine, its something to do with dry solder joints. Its possible ofcourse that the board is faulty in your case.

 

@mc - Yes, the cutting out is because the relay disconnects which cuts power to the sub. This over time can worsen so the relay is never connected so the sub never works, but replacing the relay should fix it.

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Thanks sooo much for this guide. Ive been haunted by this issue for several months now, had everything apart loads of times trying different thickness of paper/washers to no avail. With this guide, 5 mins and £2.65 i have a perfectly working sound system! Thanks for taking the time to post this.

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  • 2 weeks later...

Wahoooo fixed 👌 did it once didn't work brought it back in After i tested put a little more solder on it and now it works , cheers for sharing ðŸ‘ðŸ‘ðŸ‘

 

 

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  • 2 weeks later...
Super! Thanks for the links to eBay and step by step instructions. Will give it a go next weekend. I tried the paper method but still having issue with it! I want me back massage!

 

Put it this way I had never soldered anything before in my life and I done it ðŸ‘

 

 

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  • 7 months later...
Glad you got there in the end Zhorno :thumbs:

 

Radjordan, beat of luck. Just take your time de soldering the old and soldering in the new relay and you will be fine. In reality it's a fairly simple job ;)

 

And before you bolt everything back in , test it like I did ! Not !! Had to resolder it the it worked lol

 

 

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  • 7 months later...

Works a treat ðŸ‘🼠I tried the stuffing method but it eventually started to fail again. for anyone that isn't great with a soldering iron, if you send me your amp I'll happily replace the offending relay. As long as you cover postage & the price of the relay 😉

 

 

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  • 1 month later...

I had the same issues, I bought the replacement relay but when I got round to replacing, I couldn't find the soldering iron so went with the 'cardboard' method haha it works for the time being, at least now I have the relay for when it decides to go again.

Now just need to look out for the soldering iron .. Haha

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  • 4 weeks later...

Just to say I did my one last week, very easy and quick to do, although I needed a second pair of hands to pull the old resistor off of the board.

It seems to have sorted out the bass issue but I still have the thwack the side of the headunit (passenger footwell bit) to get the full volume out of it. :lol:

I'm not exactly sure what the cause of that is.

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  • 3 weeks later...

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