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Radio wiring

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Old Dec 10th, 2019, 12:25   #11
bob12
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I don't have any experience of a CR(cassette radio) 906 but I do in respect of the 702 and 708. At the least the oem of the 7's was Alpine, Japan.

The 7's did not have a powerful inbuilt amp unlike modern head units and that was the primary reason for the front and back door speakers being fed via din plugs from the head unit to the separate under dash amp (from where the door speakers are fed directly via loom wiring).

The 7's also had a separate speaker output that was fed via the wiring loom to small speakers on the top of either side of the dash which were only fitted to 'select' models in the range. There are no other outputs on the back of the 7's other than these two.

Bob
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Old Dec 10th, 2019, 14:51   #12
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I don't have any experience of a CR(cassette radio) 906 but I do in respect of the 702 and 708. At the least the oem of the 7's was Alpine, Japan.

The 7's did not have a powerful inbuilt amp unlike modern head units and that was the primary reason for the front and back door speakers being fed via din plugs from the head unit to the separate under dash amp (from where the door speakers are fed directly via loom wiring).

The 7's also had a separate speaker output that was fed via the wiring loom to small speakers on the top of either side of the dash which were only fitted to 'select' models in the range. There are no other outputs on the back of the 7's other than these two.

Bob
My 7 was an alpine and the car does have dash speakers so presumably then what I thought is correct. the 2 speaker outs from the radio are for the dash speakers and the speakers in the doors are fed from the amp. Is there a reason for these door speakers to fail or would it be the amp feeding them?
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Old Dec 10th, 2019, 15:04   #13
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My 7 was an alpine and the car does have dash speakers so presumably then what I thought is correct. the 2 speaker outs from the radio are for the dash speakers and the speakers in the doors are fed from the amp. Is there a reason for these door speakers to fail or would it be the amp feeding them?
Most likely the amp. Assuming you've had the speakers working of course. They can and do fail though, they're now 30 years old and the cones are (or were!) paper and usually disintegrate. This means the voice coil of the speakers moves without creating a sound.

If you have an output to the dash mounted tweeters, theory says if you run a bit of speaker wire from each of those to the door speakers, you'll hear something.
Usually tweeters are supplementary to the door speakers and have a passive crossover (usually just a capacitor in series with the tweeter) but it could be Volvo have done things differently. It might even be they're not even tweeters as most people understand them but simply fill-in speakers. Usually the door speakers are full range units in the doors.
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Old Dec 10th, 2019, 17:42   #14
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Most likely the amp. Assuming you've had the speakers working of course. They can and do fail though, they're now 30 years old and the cones are (or were!) paper and usually disintegrate. This means the voice coil of the speakers moves without creating a sound.

If you have an output to the dash mounted tweeters, theory says if you run a bit of speaker wire from each of those to the door speakers, you'll hear something.
Usually tweeters are supplementary to the door speakers and have a passive crossover (usually just a capacitor in series with the tweeter) but it could be Volvo have done things differently. It might even be they're not even tweeters as most people understand them but simply fill-in speakers. Usually the door speakers are full range units in the doors.
So could be just the speakers gone? not a bad thing to go, gives me an excuse to get nice new ones but like you say I need to check them. seeing as only one tweeter works chances are it could also be that the door speakers have gone but i'll test them with a known output from another radio and my old 708, not sure if they ever worked on that.
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Old Dec 10th, 2019, 21:37   #15
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My 7 was an alpine and the car does have dash speakers so presumably then what I thought is correct. the 2 speaker outs from the radio are for the dash speakers and the speakers in the doors are fed from the amp. Is there a reason for these door speakers to fail or would it be the amp feeding them?
I very much doubt the amp has 'blown' unless misused as they are very robust. The main problem with continuity between the amp or any bypass connector connected to it is age and dodgy flexible wiring at the hinge of any of the doors or inside the door card.

For instance, currently my door speakers all round on my all singing and dancing modern head unit in my '90 745 (using the original wiring) are playing up and randomly cutting out at times.

To remedy I just have to just tap the top of the electric door mirror switches/movers and bingo sound is restored!! Bizarre!!

The final fix will be revealed, I am sure, when the door cards are removed but, not until next Summer!

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Old Dec 10th, 2019, 21:41   #16
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Most likely the amp. Assuming you've had the speakers working of course. They can and do fail though, they're now 30 years old and the cones are (or were!) paper and usually disintegrate. This means the voice coil of the speakers moves without creating a sound.

If you have an output to the dash mounted tweeters, theory says if you run a bit of speaker wire from each of those to the door speakers, you'll hear something.
Usually tweeters are supplementary to the door speakers and have a passive crossover (usually just a capacitor in series with the tweeter) but it could be Volvo have done things differently. It might even be they're not even tweeters as most people understand them but simply fill-in speakers. Usually the door speakers are full range units in the doors.
Volvo head units of that era and their associated wiring are a world away from modern logic/common sense and accepted principles!!
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Old Dec 10th, 2019, 21:49   #17
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So could be just the speakers gone? not a bad thing to go, gives me an excuse to get nice new ones but like you say I need to check them. seeing as only one tweeter works chances are it could also be that the door speakers have gone but i'll test them with a known output from another radio and my old 708, not sure if they ever worked on that.
Again, the speakers are robust and I really can't believe that the lot are busted unless severely abused. You will have to do some continuity tests on the wiring and check the speakers are working by connecting them to a known good output. Bob
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Old Dec 10th, 2019, 21:58   #18
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Again, the speakers are robust and I really can't believe that the lot are busted unless severely abused. You will have to do some continuity tests on the wiring and check the speakers are working by connecting them to a known good output. Bob
Speakers on my last 740 had no cones left Bob, just rotted away. Two of the speakers on this 760 were the same. All cones were split/damaged/missing on both cars though.
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Old Dec 10th, 2019, 22:46   #19
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Speakers on my last 740 had no cones left Bob, just rotted away. Two of the speakers on this 760 were the same. All cones were split/damaged/missing on both cars though.
As I was trying to say ... you gotta start getting a bit brutal to find out where the usually simple solution to a problem like resides. Bob
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Old Dec 13th, 2019, 13:33   #20
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So I think I found the reason the front door speakers not working... they simply aren't there!



Taking the door card off completely showed the wires glued on the door behind! Only issue is these have no power to them, tried a 6x9 speaker which is big but I had one to hand and nothing from it. I checked continuity from the amp and there is continuity.

What could be the cause for no power, amp not putting anything out? What is the output of the amp too, I plan on getting some speakers but not sure what output the amp gives.


Last edited by ANDTWENTY; Dec 13th, 2019 at 13:46.
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