The Delco Bose sound system fitted to the C4 has a reputation for unreliability, particularly with the active speaker amplifiers that are found in each speaker pod. There are two speakers in the rear compartment and two in the sills at the front of the footwell. This reputation comes from the bad habit that the electrolytic capacitors have of leaking fluid over the circuit board. Unfortunately the fluid is both corrosive and conducts electricity (probably a necessary characteristic but unfortunate when it gets out of the can).
When the fluid leaks it flows on to the power transistors and shorts them out causing a significant heat build up and destroying the amplifier. When removing my rear speaker units I became aware of a burnt plastic smell but was still a bit shocked by the condition of the passenger side unit (see pic) which may have come close to torching the whole car, at some point in its history. Both power transistors on the left hand side have cracked with the heat and the circuit board around them is destroyed with mid-layer tracks exposed. The circuits don't seem to have a fuse so continue to suck up current until something else blows catastrophically.
I'd recommend anyone with a C4 whose speakers sound scratchy or don't produce any sound at all to have a quick look at the amplifiers (it takes about 15-20 mins each side at the rear, a bit longer at the front) and see if they are at risk.
The two capacitors either side of the central coil are the main culprits.
The drivers side amplifier board was much better. The capacitors have leaked but don't appear to have caused the same short circuits - as far as I can see. However, I have swapped out all the electrolytic capacitors and it still doesn't work so either further electrical damage has been done to the amp or the head unit (or I screwed up replacing the capacitors). Further testing will hopefully show what has gone wrong.
First as-is, straight out of the car ....
and then with the capacitors replaced (now black and red, were brown and green).....
You can't see from the plan view but the two capacitors that I fitted each side of the central coil are too tall and the heat sink/suppressor shield doesn't now fit. Once I have figured out electrically what is wrong I will replace these two (again) with the proper physical size. If both boards are ruined (at least one is) I will have to get a new rear set.
The front speakers are also not producing a decent sound so they will be inspected next week. If I'm unlucky I will need a complete set - another reason to check earlier rather than later if your system isn't working. The good news is that new boards are available at a reasonable price although if you need four the costs mount up..... The NVR brand speakers are good (still seem to be being made today) but apparently they are an unusually low impedance - 2 ohms - in this installation. Apparently, the same (or probably similar) system was used on the contemporary Honda NSX. There is some good information on the BOSE system on one of the NSX forums.
Incidentally all the replacement capacitors are available fairly cheaply from Radio Spares (I can supply part numbers if anyone is interested) and replacing them takes about an hour once the board is on the bench. You need a soldering iron, a desoldering tool, some solder and a few tools (screwdrivers and pliers).
I'll provide an update when I have looked at the front speakers. Hopefully I can work out what has gone wrong with the drivers side rear unit too by then. Fingers crossed...
When the fluid leaks it flows on to the power transistors and shorts them out causing a significant heat build up and destroying the amplifier. When removing my rear speaker units I became aware of a burnt plastic smell but was still a bit shocked by the condition of the passenger side unit (see pic) which may have come close to torching the whole car, at some point in its history. Both power transistors on the left hand side have cracked with the heat and the circuit board around them is destroyed with mid-layer tracks exposed. The circuits don't seem to have a fuse so continue to suck up current until something else blows catastrophically.
I'd recommend anyone with a C4 whose speakers sound scratchy or don't produce any sound at all to have a quick look at the amplifiers (it takes about 15-20 mins each side at the rear, a bit longer at the front) and see if they are at risk.
The two capacitors either side of the central coil are the main culprits.
The drivers side amplifier board was much better. The capacitors have leaked but don't appear to have caused the same short circuits - as far as I can see. However, I have swapped out all the electrolytic capacitors and it still doesn't work so either further electrical damage has been done to the amp or the head unit (or I screwed up replacing the capacitors). Further testing will hopefully show what has gone wrong.
First as-is, straight out of the car ....
and then with the capacitors replaced (now black and red, were brown and green).....
You can't see from the plan view but the two capacitors that I fitted each side of the central coil are too tall and the heat sink/suppressor shield doesn't now fit. Once I have figured out electrically what is wrong I will replace these two (again) with the proper physical size. If both boards are ruined (at least one is) I will have to get a new rear set.
The front speakers are also not producing a decent sound so they will be inspected next week. If I'm unlucky I will need a complete set - another reason to check earlier rather than later if your system isn't working. The good news is that new boards are available at a reasonable price although if you need four the costs mount up..... The NVR brand speakers are good (still seem to be being made today) but apparently they are an unusually low impedance - 2 ohms - in this installation. Apparently, the same (or probably similar) system was used on the contemporary Honda NSX. There is some good information on the BOSE system on one of the NSX forums.
Incidentally all the replacement capacitors are available fairly cheaply from Radio Spares (I can supply part numbers if anyone is interested) and replacing them takes about an hour once the board is on the bench. You need a soldering iron, a desoldering tool, some solder and a few tools (screwdrivers and pliers).
I'll provide an update when I have looked at the front speakers. Hopefully I can work out what has gone wrong with the drivers side rear unit too by then. Fingers crossed...
