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I have worked on all 4 Bose amps over the years and fixed all the popping and squealing so when the left front started making weird squealing sounds I was surprised. After I got the amp out I checked all the caps I put in with a capacitance meter and all looked good. Then I noticed one lone capacitor C16, never replaced. As I moved it one lead of the capacitor came right out of the bottom of the cap. The kicker is in the documentation I have it says C16 is only used in convertibles. Be as it may, I replaced the 1.0 ufd cap and all is good again. Bench tested it, back in the car and it's normal again. Guess I missed replacing that cap last time but at that time it was good.
Trim on rocking panel removed, just a few screws.
Speaker box on side of car, just 4 screws
Speaker box
Rear of speaker box with amplifier board removed.
Amplifier removed from speaker box
Circuit card with shields removed. You can see C16 laying on side. One lead came out of the cap.
C16 detail of defective capacitor. (picture sucks I know, to close)
Though I would put some info up for those who might think about fixing there Bose amps. Not very hard to remove, install and work on. This is the easy stuff to work on and fun for me.
Had the whole system (head, cdm and amps) shipped from Europe to Florida to be repaired a few years ago.
Still works OK, but today the rear left speaker started popping.
Not constantly, only a pop in a while, on one CD, so it could have been a glitch on that one.
Problem for me is only, how to measure the different caps and other "buildings" on the circuit cards.
Can it be done with an average digital volt/ohm meter?
If so, what scale?
Parts won´t be a problem, as long I can find out the values on those, I can get them here.
Had the whole system (head, cdm and amps) shipped from Europe to Florida to be repaired a few years ago.
Still works OK, but today the rear left speaker started popping.
Not constantly, only a pop in a while, on one CD, so it could have been a glitch on that one.
Problem for me is only, how to measure the different caps and other "buildings" on the circuit cards. Can it be done with an average digital volt/ohm meter?
If so, what scale?Parts won´t be a problem, as long I can find out the values on those, I can get them here.
If you look at the circuit card picture, the 3 main caps that go bad are the ones that are 4 in a row (3 brown and a green). The two larger black caps more toward the rear are 47 ufd and I found these not to be bad as often. On this board I did not replace these caps either last time or this time, they still check 47 ufd. The other 2 biggest caps (C19 is one) I don’t bother to replace these. I have never found them bad but mainly because they are low profile caps @ 750 ufd and to find one this physical size is a problem. Anything 1000 to 750 will work but you will have to cut the shield….no me if there still good. And of course don’t forget to replace C16 with the other 4 small ones.
I think now I can hear a bit of a squeal from my right side in the car. I will probably will have to do that one in the near future but is not as bad as the left was at this point in time. BTW, all the little caps are 1 and 10 ufd @ 16vdc.
In regard to your question on using a ohm meter to check capacitors. In the past 30 years or so we did that and was a crude and not accurate method but that’s all we because capacitance testers were expensive. Even the last few years at work I was using some of the capacitance testers for myself. But one day I decided to have my own and checked EBay. I found them for $16 with shipping and ordered one. There are more expensive ones and all have multi-meter functions but I only cared about the one feature. This capacitance meter works great I just could not believe it. The highest it will measure is 200, but goes below 1mfd which is the area you are most interested in. (I did want to measure more than 200 but just did not want to spend the money. But this works just fine). Most of the caps that go bad just don’t change 50 or 70% of rated value. They go in to the pf range which is basically is 0.0 of useable capacitance for coupling or decoupling capacitors, they really go south.
So what I'm saying is don’t waste your time with a ohm meter trying to measure them. But a cheap capacitance meter for under $25 and you will be real happy.
If you look at the circuit card picture, the 3 main caps that go bad are the ones that are 4 in a row (3 brown and a green). The two larger black caps more toward the rear are 47 ufd and I found these not to be bad as often. On this board I did not replace these caps either last time or this time, they still check 47 ufd. The other 2 biggest caps (C19 is one) I don’t bother to replace these. I have never found them bad but mainly because they are low profile caps @ 750 ufd and to find one this physical size is a problem. Anything 1000 to 750 will work but you will have to cut the shield….no me if there still good. And of course don’t forget to replace C16 with the other 4 small ones.
I think now I can hear a bit of a squeal from my right side in the car. I will probably will have to do that one in the near future but is not as bad as the left was at this point in time. BTW, all the little caps are 1 and 10 ufd @ 16vdc.
In regard to your question on using a ohm meter to check capacitors. In the past 30 years or so we did that and was a crude and not accurate method but that’s all we because capacitance testers were expensive. Even the last few years at work I was using some of the capacitance testers for myself. But one day I decided to have my own and checked EBay. I found them for $16 with shipping and ordered one. There are more expensive ones and all have multi-meter functions but I only cared about the one feature. This capacitance meter works great I just could not believe it. The highest it will measure is 200, but goes below 1mfd which is the area you are most interested in. (I did want to measure more than 200 but just did not want to spend the money. But this works just fine). Most of the caps that go bad just don’t change 50 or 70% of rated value. They go in to the pf range which is basically is 0.0 or useable capacitance for coupling or decoupling capacitors, they really go south.
So what I'm saying is don’t waste your time with a ohm meter trying to measure them. But a cheap capacitance meter for under $25 and you will be real happy.
I have a bad driver side front speaker amp on my 94 coupe. I tried installin some new capacitors(the big two big ones) because I thought those were the bad ones from previous threads I had read. They were tough to get out, I have not used a soldering iron in a long time. It did not improve the low volume and noise problem.
So the smaller capacitors are more likely to be bad? Can I buy a capacitor tester at radio shack?
If you look at the circuit card picture, the 3 main caps that go bad are the ones that are 4 in a row (3 brown and a green). The two larger black caps more toward the rear are 47 ufd and I found these not to be bad as often. On this board I did not replace these caps either last time or this time, they still check 47 ufd. The other 2 biggest caps (C19 is one) I don’t bother to replace these. I have never found them bad but mainly because they are low profile caps @ 750 ufd and to find one this physical size is a problem. Anything 1000 to 750 will work but you will have to cut the shield….no me if there still good. And of course don’t forget to replace C16 with the other 4 small ones.
I think now I can hear a bit of a squeal from my right side in the car. I will probably will have to do that one in the near future but is not as bad as the left was at this point in time. BTW, all the little caps are 1 and 10 ufd @ 16vdc.
In regard to your question on using a ohm meter to check capacitors. In the past 30 years or so we did that and was a crude and not accurate method but that’s all we because capacitance testers were expensive. Even the last few years at work I was using some of the capacitance testers for myself. But one day I decided to have my own and checked EBay. I found them for $16 with shipping and ordered one. There are more expensive ones and all have multi-meter functions but I only cared about the one feature. This capacitance meter works great I just could not believe it. The highest it will measure is 200, but goes below 1mfd which is the area you are most interested in. (I did want to measure more than 200 but just did not want to spend the money. But this works just fine). Most of the caps that go bad just don’t change 50 or 70% of rated value. They go in to the pf range which is basically is 0.0 or useable capacitance for coupling or decoupling capacitors, they really go south.
So what I'm saying is don’t waste your time with a ohm meter trying to measure them. But a cheap capacitance meter for under $25 and you will be real happy.
You can measure larger capacitors than your meter goes to by connecting a known capacitor in series with the capacitor you are measuring and then calculate the value of the capacitor you are measuring.
C(unknown) = 1/( 1/C(total) -1/C(known))
unknown = cap you are trying to measure
total = capacitance of the two capacitors in series
known = capacitance of the added series capacitor
You can measure larger capacitors than your meter goes to by connecting a known capacitor in series with the capacitor you are measuring and then calculate the value of the capacitor you are measuring.
C(unknown) = 1/( 1/C(total) -1/C(known))
unknown = cap you are trying to measure
total = capacitance of the two capacitors in series
known = capacitance of the added series capacitor
Interesting concept and method for finding the unknown.
Surly I recognize the formula for finding the value for capacitors in series (and still use it). Seem so obvious since I have know the equation since ham radio days, school or whatever from the 60s. (Way before collage).
Interesting concept and method for finding the unknown.
Surly I recognize the formula for finding the value for capacitors in series (and still use it). Seem so obvious since I have know the equation since ham radio days, school or whatever from the 60s. (Way before collage).
Just better utilization of my meter, Thanks.
I was thinking, "I bet this will just jog his memory".
I have a bad driver side front speaker amp on my 94 coupe. I tried installin some new capacitors(the big two big ones) because I thought those were the bad ones from previous threads I had read. They were tough to get out, I have not used a soldering iron in a long time. It did not improve the low volume and noise problem.
So the smaller capacitors are more likely to be bad? Can I buy a capacitor tester at radio shack?
The smaller capacitors (1 & 10 ufd) are the ones that go bad. Capacitor C172 is the one that will affect volume and sound quality. The rest will make the squeaks and squeals.
I don’t think you will find a capacitance tester in Radio Shack. They are not the store they once were selling electronic parts as they once did, it's now very limited. They want to sell you consumer stuff like cameras, telephones stereos and basic meters. Capacitance testers are not run of the mill test equipment for you average consumer. Most people buy a DVM or multimeter for basic troubleshooting. Capacitance testers use to cost a lot and weight a lot with many functions as most people would not know how to use.
But due to technology and China, you can but a cap meter that is simple to work, does a basic test and cheep to produce and good for home periodic use. I never knew they were than cheap to buy till I looked at EBay. Never saw one in any store of that type.
If you want more information on the Bose amps, check this thread. It will give you additional information plus links to the schematics and other peoples research.
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Fixing Bose Amps one more time.
