Loud hum from Bose rear speakers
07-25-08 | 03:13 PM
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From: Orange County, CA, USA
Loud hum from Bose rear speakers
Posted this in the audio section but got no response so decided to try it here.
My rear Bose speakers suddenly started to make a very loud low frequency hum. The head unit volume control has no effect on it. The front and side speakers are working OK. The rear Bose units have no head-unit-based sound - just the loud hum. The hum is coming from both of the speakers.
So, now to my questions:
1) Where exactly are the rear amps located? Inside the "Bose tubes?" In a separate box somewhere?
2) What do I have to remove to get to the rear amps?
My diagnosis so far is that the inputs to the rear amps are open circuit and I just have the normal situation as would be found with any o/c input on any amp, (hum). So one would think that the cause is likely that the plug that supplies the inputs to the rear amp(s) has simply fallen out of the amp. socket. The schematic confirms that the same plug is used for both amps. Great-the diagnosis seems good so far. However, also according to the schematic, the power to the rear amps uses the same plug as the inputs! The power is clearly getting to the rear amps (i.e. loud hum!) so, unless the connector is slightly out of its socket and the power pins are longer than input pins, (possible but unlikely), my diagnosis doesn't fit.
The same situation exists if I assume it is the head unit plug for the rear amps that has fallen out. However, once again, the output pins and the power for the rear amps share the same plug at the head unit. So I'm stumped.
It seems unlikely that both rear amps went bad together. It also seems unlikely that both head outputs to the rear amps went bad together. However, those are the only two possibilities left (I think).
Has anybody had the same problem? Any ideas what else could be causing the problem?
Thanks
Dave
My rear Bose speakers suddenly started to make a very loud low frequency hum. The head unit volume control has no effect on it. The front and side speakers are working OK. The rear Bose units have no head-unit-based sound - just the loud hum. The hum is coming from both of the speakers.
So, now to my questions:
1) Where exactly are the rear amps located? Inside the "Bose tubes?" In a separate box somewhere?
2) What do I have to remove to get to the rear amps?
My diagnosis so far is that the inputs to the rear amps are open circuit and I just have the normal situation as would be found with any o/c input on any amp, (hum). So one would think that the cause is likely that the plug that supplies the inputs to the rear amp(s) has simply fallen out of the amp. socket. The schematic confirms that the same plug is used for both amps. Great-the diagnosis seems good so far. However, also according to the schematic, the power to the rear amps uses the same plug as the inputs! The power is clearly getting to the rear amps (i.e. loud hum!) so, unless the connector is slightly out of its socket and the power pins are longer than input pins, (possible but unlikely), my diagnosis doesn't fit.
The same situation exists if I assume it is the head unit plug for the rear amps that has fallen out. However, once again, the output pins and the power for the rear amps share the same plug at the head unit. So I'm stumped.
It seems unlikely that both rear amps went bad together. It also seems unlikely that both head outputs to the rear amps went bad together. However, those are the only two possibilities left (I think).
Has anybody had the same problem? Any ideas what else could be causing the problem?
Thanks
Dave
