Question about Bose Acoustimass 15 System
All speakers are working but the bass speaker is not working.
How should i fix this?
Please let me know
Cube speakers are working, but base unit is not. Took off the back, fuse okay, need help.
OK, Bose owners out there listen up and
listen good. Here's the real scoop on 1.(getting access to the inside of most
bose subwoofers, 2.( repairing said subwoofer.
Follow these steps in removing the cover of your subwoofer. Unscrew the two screws from the cover. (They are on the input/output side of the cover) Remove the two knobs (Bass and treble volume).
On the opposite side of the cover, (put those damn shoes back in the closet) there is a lockout tab that needs to be swung out, it moves 90 degrees in a counter-clockwise direction and is located under the center of the cover.
A small flat blade screwdriver works great for swinging this tab out and will be necessary for the next step (the screwdriver that is).
On the same side (opposite the input/output side) there are two small tabs near the edges of the cover, one on the right and it's counterpart on the left. If you look closely in the gap between the cover and the sub itself, you will see these 3/8" wide tabs near the edges and towards the top of the cover.
With the flat blade screwdriver, put the blade between the cover and on the tab and pull down. Then with your hand balled into a fist, gently hit that side of the cover towards the input/output side. the cover will move only slightly but the tab should remain depressed.
Do the same procedure on the opposite side of the cover and it will slide about a 1/2 to 3/4" towards the input/output side and can then be removed by pulling it straight up and off of the cabinet.
Yay! If you get this far without incident then you are ready to implement repairs. In the case of the AM15's, normally what happens is a resistor will open up and prevent the triac (turn-on device) from firing.
The fuse is on the underside of the PC board and this above mentioned resistor is a 100 ohm, surface mount "chip" resistor on the top side of the PC board. It will not appear to be bad but trust me, if the fuse is good and the sub will not turn on... replace it!
You don't have to use a chip resistor since as a consumer you may have a rough time finding one but a 1/8 watt or 1/4 watt resistor you can find at any Radio Shack will work just dandy in this application.
Cut the leads short and solder the two cut leads to the pads on the circuit board where the chip resistor is currently sitting. The chip resistor will be black, about 1/4" long, 1/8" wide and have "101" printed on it's surface. On some models they used two 200 ohm resistors in parallel but the result is the same. One 1/4w axial lead resistor will do just fine. Plug it up and give it a try. (Before you replace the cover).
Secondly, if the fuse is blown on a "Lifestyle" Bose subwoofer, contrary to popular belief, it blew for a reason. The speaker outputs and the subwoofer output devices are TDA7294 IC's with TIP142 and TIP147 Motorola transistors used as current supplements to these said output devices. If the fuse is blown and replacing it only results in another blown fuse then chances are good that one or more of these are blown. In some cases it's very easy to tell, the front of these IC's will be blown off and/or you will see burn marks on the board where they are mounted. These devices are located inside the amp portion of the subwoofer. (The black metal heatsink underneath the input/preamp PCB. As a consumer, if the fuse is blown, unless you are familiar with soldering techniques and troubleshooting electronics, leave this to the pro's. It isn't as easy as you might think and you can destroy the PCB in your attempts to repair it.
This was from a Guru of Bose systems at ecoustics.com: Mark Burgess
Posted on May 11, 2008
If you cant open the bass speaker dont force it open. You will only damage it, and if the housing is damaged then you will have ruined the sound quality. A simple way of checking a speaker to see if it works is.
1. Disconnect all the connections to the speaker.
2. Take a small length of wire, about 2 feet. Connect one end of it to the Bass input of the speaker.
3. Get a "D" size 1.5 volt battery cell. The other side of the wire, dont connect it to the battery but just hold it with your hand to both ends of the battery, for just a couple of seconds at a time.
4. If you hear a humming sound from the speaker, when you have made the connection to the battery then the speaker is good.
You must be having another problem. My suggestion is try another CD from your collection, not a pirated one. If still no positive results then spend some money and get it done through Bose service center.
Posted on May 11, 2008
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