Radio pre-set buttons stopped working - Cause found
#1
03-10-2019, 08:40 PM
Radio pre-set buttons stopped working - Cause found
The #2 (second radio preset) and #8 (FM source) buttons stopped working about a year ago. I finally got around to doing a disassembly to figure out what the cause was and to see if it was fixable. I wasn't able to fix it, but figured I'd share my experience.
I did the full tear down to get the speedo and stereo receiver out of the dash. Once I got everything disassembled I gave the button contacts a good look and didn't see anything too unusual - this wasn't a simple mechanical failure I had hoped to find. I got out my multimeter and started taking measurements of the good and bad buttons. It appears that all of the buttons are supplied with 5V which is sent to ground as the button completes the circuit. The failed buttons weren't getting the 5V like the others were. Interestingly the #2 and #8 buttons share the same 5V circuit which explains why just those two failed at the same time.
I started probing my way back to see if I could find a smoking gun on that 5V supply trace. Everything in the speedo assembly checked out I was getting fully continuity from the button contacts out to the ribbon cable (there is a ribbon cable that connects the back of the speedo to the CD/receiver). Whatever the problem was it wasn't with the speedo assembly.
Following the trace/ribbon to the CD receiver I did a full tear down to resume the search. I finally found the open circuit in that trace and the smoking gun I was looking for. The #2/#8 button 5V trace reverses to the backside of the circuit board via a copper plated eyelet/through hole in the board. That eyelet on my trace had corroded and was no longer making electrical contact. I also noticed three other eyelets had serious corrosion going on as well, not sure what circuits those supported, but I'm sure they would have failed eventually.
A repair seemed doable, but I don't have any confidence in my ability to solder items that small. Replacement receivers are pretty reasonable (though new ones are $1000+). Should the supply of used receivers dry up I'm sure some electronics repair shop could fix the PCB in a few minutes.
The first picture below shows the corroded eyelets. The 2nd corroded eyelet from the left was the one that should have been supplying 5V to my #2 and #8 radio buttons.
https://imgur.com/a/Ly4PEeM
In this picture you can get a feel for where this board is located in the assembly, it's mounted vertically just behind the faceplate of the CD slot. If you look closely at the felt just above the CD slot you can see where the corrosion stained the felt. I'm sure that felt was added to prevent vibrations, but I believe it may have trapped some moisture against the circuit board.
https://imgur.com/a/F3XTOEt
My mini is a spare car so it sometimes goes a month without being driven in Seattle weather. Had I driven this car more I suspect the heat from the electronics and extra air circulation may have helped prevent this. I was getting ready to pull the trigger on a replacement speedo assembly; glad I took the time to dig into it and figure out it was really the cd receiver that needed to be replaced.
I did the full tear down to get the speedo and stereo receiver out of the dash. Once I got everything disassembled I gave the button contacts a good look and didn't see anything too unusual - this wasn't a simple mechanical failure I had hoped to find. I got out my multimeter and started taking measurements of the good and bad buttons. It appears that all of the buttons are supplied with 5V which is sent to ground as the button completes the circuit. The failed buttons weren't getting the 5V like the others were. Interestingly the #2 and #8 buttons share the same 5V circuit which explains why just those two failed at the same time.
I started probing my way back to see if I could find a smoking gun on that 5V supply trace. Everything in the speedo assembly checked out I was getting fully continuity from the button contacts out to the ribbon cable (there is a ribbon cable that connects the back of the speedo to the CD/receiver). Whatever the problem was it wasn't with the speedo assembly.
Following the trace/ribbon to the CD receiver I did a full tear down to resume the search. I finally found the open circuit in that trace and the smoking gun I was looking for. The #2/#8 button 5V trace reverses to the backside of the circuit board via a copper plated eyelet/through hole in the board. That eyelet on my trace had corroded and was no longer making electrical contact. I also noticed three other eyelets had serious corrosion going on as well, not sure what circuits those supported, but I'm sure they would have failed eventually.
A repair seemed doable, but I don't have any confidence in my ability to solder items that small. Replacement receivers are pretty reasonable (though new ones are $1000+). Should the supply of used receivers dry up I'm sure some electronics repair shop could fix the PCB in a few minutes.
The first picture below shows the corroded eyelets. The 2nd corroded eyelet from the left was the one that should have been supplying 5V to my #2 and #8 radio buttons.
https://imgur.com/a/Ly4PEeM
In this picture you can get a feel for where this board is located in the assembly, it's mounted vertically just behind the faceplate of the CD slot. If you look closely at the felt just above the CD slot you can see where the corrosion stained the felt. I'm sure that felt was added to prevent vibrations, but I believe it may have trapped some moisture against the circuit board.
https://imgur.com/a/F3XTOEt
My mini is a spare car so it sometimes goes a month without being driven in Seattle weather. Had I driven this car more I suspect the heat from the electronics and extra air circulation may have helped prevent this. I was getting ready to pull the trigger on a replacement speedo assembly; glad I took the time to dig into it and figure out it was really the cd receiver that needed to be replaced.
#2
08-13-2021, 08:07 PM
The #2 (second radio preset) and #8 (FM source) buttons stopped working about a year ago. I finally got around to doing a disassembly to figure out what the cause was and to see if it was fixable. I wasn't able to fix it, but figured I'd share my experience.
I did the full tear down to get the speedo and stereo receiver out of the dash. Once I got everything disassembled I gave the button contacts a good look and didn't see anything too unusual - this wasn't a simple mechanical failure I had hoped to find. I got out my multimeter and started taking measurements of the good and bad buttons. It appears that all of the buttons are supplied with 5V which is sent to ground as the button completes the circuit. The failed buttons weren't getting the 5V like the others were. Interestingly the #2 and #8 buttons share the same 5V circuit which explains why just those two failed at the same time.
I started probing my way back to see if I could find a smoking gun on that 5V supply trace. Everything in the speedo assembly checked out I was getting fully continuity from the button contacts out to the ribbon cable (there is a ribbon cable that connects the back of the speedo to the CD/receiver). Whatever the problem was it wasn't with the speedo assembly.
Following the trace/ribbon to the CD receiver I did a full tear down to resume the search. I finally found the open circuit in that trace and the smoking gun I was looking for. The #2/#8 button 5V trace reverses to the backside of the circuit board via a copper plated eyelet/through hole in the board. That eyelet on my trace had corroded and was no longer making electrical contact. I also noticed three other eyelets had serious corrosion going on as well, not sure what circuits those supported, but I'm sure they would have failed eventually.
A repair seemed doable, but I don't have any confidence in my ability to solder items that small. Replacement receivers are pretty reasonable (though new ones are $1000+). Should the supply of used receivers dry up I'm sure some electronics repair shop could fix the PCB in a few minutes.
The first picture below shows the corroded eyelets. The 2nd corroded eyelet from the left was the one that should have been supplying 5V to my #2 and #8 radio buttons.
https://imgur.com/a/Ly4PEeM
In this picture you can get a feel for where this board is located in the assembly, it's mounted vertically just behind the faceplate of the CD slot. If you look closely at the felt just above the CD slot you can see where the corrosion stained the felt. I'm sure that felt was added to prevent vibrations, but I believe it may have trapped some moisture against the circuit board.
https://imgur.com/a/F3XTOEt
My mini is a spare car so it sometimes goes a month without being driven in Seattle weather. Had I driven this car more I suspect the heat from the electronics and extra air circulation may have helped prevent this. I was getting ready to pull the trigger on a replacement speedo assembly; glad I took the time to dig into it and figure out it was really the cd receiver that needed to be replaced.
I did the full tear down to get the speedo and stereo receiver out of the dash. Once I got everything disassembled I gave the button contacts a good look and didn't see anything too unusual - this wasn't a simple mechanical failure I had hoped to find. I got out my multimeter and started taking measurements of the good and bad buttons. It appears that all of the buttons are supplied with 5V which is sent to ground as the button completes the circuit. The failed buttons weren't getting the 5V like the others were. Interestingly the #2 and #8 buttons share the same 5V circuit which explains why just those two failed at the same time.
I started probing my way back to see if I could find a smoking gun on that 5V supply trace. Everything in the speedo assembly checked out I was getting fully continuity from the button contacts out to the ribbon cable (there is a ribbon cable that connects the back of the speedo to the CD/receiver). Whatever the problem was it wasn't with the speedo assembly.
Following the trace/ribbon to the CD receiver I did a full tear down to resume the search. I finally found the open circuit in that trace and the smoking gun I was looking for. The #2/#8 button 5V trace reverses to the backside of the circuit board via a copper plated eyelet/through hole in the board. That eyelet on my trace had corroded and was no longer making electrical contact. I also noticed three other eyelets had serious corrosion going on as well, not sure what circuits those supported, but I'm sure they would have failed eventually.
A repair seemed doable, but I don't have any confidence in my ability to solder items that small. Replacement receivers are pretty reasonable (though new ones are $1000+). Should the supply of used receivers dry up I'm sure some electronics repair shop could fix the PCB in a few minutes.
The first picture below shows the corroded eyelets. The 2nd corroded eyelet from the left was the one that should have been supplying 5V to my #2 and #8 radio buttons.
https://imgur.com/a/Ly4PEeM
In this picture you can get a feel for where this board is located in the assembly, it's mounted vertically just behind the faceplate of the CD slot. If you look closely at the felt just above the CD slot you can see where the corrosion stained the felt. I'm sure that felt was added to prevent vibrations, but I believe it may have trapped some moisture against the circuit board.
https://imgur.com/a/F3XTOEt
My mini is a spare car so it sometimes goes a month without being driven in Seattle weather. Had I driven this car more I suspect the heat from the electronics and extra air circulation may have helped prevent this. I was getting ready to pull the trigger on a replacement speedo assembly; glad I took the time to dig into it and figure out it was really the cd receiver that needed to be replaced.
Thread
Thread Starter
Forum
Replies
Last Post