Sound system advice.
 

Hey guys,

I very rarely use my C70, buuuuuut as of late I find myself using it more than my bicycle due to the amount of running around I seem to have taken on.

I remember posting about this before, but I have the premium sound system amplified and it does sound awesome, when it works. 99% of the time it sucks. Hissing, whining through the speakers, right door not working, then the bass not working. Then you hit a bump or make a turn and it booms back in. Then its off again. Hell even when you are stationary it plays up. You can usually cure it by pulling the boot or petrol flap over and over until it 'knocks' it back on to work properly. So, I have lived with it and just driven around with my petrol flap constantly open.

But, I decided I wanted to investigate further and after inspecting ever door and speaker, I can confirm they all work and getting power and nothing cut or corroded or missing. SO, I can only assume the SC901 head unit is no longer working. Which is a shame as I would look to keep it looking stock with the iPod adapter, but I can't listen to hissy and whining music, you can drown it out by turning the volume but it blows your head off if it kicks back in and doubles in volume again and the switching of the petrol and boot no longer works as intended. A bench test came back okay, but it can't be anything else. I thought about another earth off the antenna but the current is like the day it left the factory. But, it gets incredibly hot, almost scary hot.

I guess I would like to hear some feedback from anyone who has used one of these kits here and whether it truly allowed you to just swap the head unit and use the current amps and speaker set up without compromising sound quality or clarity? I give up on all else and am not really in the mood to continue testing the same old stuff or pay an auto electrician.

http://www.ebay.co.uk/itm/3508432792...84.m1423.l2649

sounds like a loose or broken wire, just check the plug and the back of head unit , also the speaker connection,if the other two options dont fix it, but it does sound like losse connection m8 :)

Cheers for the response, we've spent £300+ on auto electricians who can't solve it, one fixed it for about a week, but it came back. Everything is in tact and a lot of wiring I have cleaned up and soldered better connections. I assumed it would be nothing more than a dodgy connection but everything is secure and as you would expect. Nothing reads irregular on the tester either...

It's a real strange one, I have even insulated some connections to be on the safe side. I cna't get my head around it. If it's not the head unit, I think I may have to sell the car it's getting that bad... :(

Start with the 6 pin DIN plug that goes in to the rear of the head unit and the other end of the cable which goes in to the amp, if this is breaking down then you will have plenty of issues with sound dropping out and hissing from the amp, as you can hear the hissing the speakers and output from the amp must be connected (otherwise it would be silence) so go after the input feeder to the amp which is the DIN plug lead - Mike

Thanks for the info... I assume to chase this all the way to the amp from the back? The whining seems to pickup electrical noises on the car, speeds up with engine, enhances sound of indicators etc... It's like a cross between a hiss and a whine... I have to try and release the passenger side motors on the seat on the weekend, I will have a look and chase the wire all the way down. See if anything is a miss there.

Thanks, I will keep updated. If no luck, I do have a test head unit to try this adapter. Don't fancy switching the whole system... Don't even have the money for that! :D lol

What you describe sounds like Ground Loop Interference, this is often caused by different voltages at the point where the amp earths to the car body relate to the ground point used by the car head unit. You can purchase GLI filters but they use RCA plugs so more adapters to go from din to rca then back to din would be required to try one of these.

I would make sure the amps earth connection is clean, if possible remove the bolt from the earth point and clean up the tags/ structure where it connects to the car before bolting it back up. The earth point for the amp is 31/11 which can be found here:

http://imageshack.com/scaled/large/194/k6ec.jpg

The main earth point for the head unit is back at the fuse/ relay box under the dash looking up between the pedals it can be seen, far from easy to get at that one - Mike

Gotta agree with Mike there - definately smacks of an earthing problem to me.

You'd think wouldn't you, I have put in an extra earth from the antenna. I had the whole boot stripped and every point checked. The only thing I haven't done is check the DIN cable from the amp to the head unit. The head unit has perfect connections all round... The one point I haven't checked is the earthing point under the fuse box you mention. I've had a quick look this afternoon and I think I can see where you mean. I have a semi built cockpit at the moment as the headlight switch was causing an issue where it had snapped. Funny enough, since replacing that switch the petrol flap and boot lid trick stopped working.

I will dedicate my morning tomorrow to it, I will again check the 31/11 area and do what you have suggested, see if anything I may have missed. It's certainly possible, I have been over the entire accessible loom.

I ordered a cable and ISO to test a head unit I have here as well, so with some luck I should have a solution tomorrow whether it be factory or aftermarket.

I'll let you know how I get on, either way. Thanks so far :)

When you locate 31/11 and take the bolt out if you can see the copper wires through the crimp see if they are still copper coloured or have they turned black, it might be water ingress down the cable that has oxidised the copper turning it black which makes it higher resistance - Mike

Right, had a few hours doing odd jobs and I dismantled the boot and amplifier. I checked all earth poi tz again and they are as new as the day they left the factory.

However, upon playinv with the 6 pin din it sprang into life again. A few more wiggles and it was in and out. The rubber seems a little dry but nothingout of the ordinary. I am going to check the amp connection and try running a new din for a few days and see how I get on. It would seem a bit of damp may have been in there at some point but nothing to cause any corrosion to wiri g.

I will see if the new cable solves it first, but if the amp is the problem I need to think again what I am going to do. I'll uodate the post when new cable arrives.

Thanks for the directions again... after checking it all before I am shocked that this time it seems to have shown something that could be causinv it. 5th time lucky by my count! Well I hope anyways. Dash/hwad unit earth was fine az well.

Reading the thread for the first time, all of the symptoms pointed to the signal wiring somewhere before the amplifier, and the fact that you heard whistles and pops from the speakers even when the music didn't get through means the signal is being lost before it got to the amps, as someone else has said previously.

The trouble with broken wires in the signal loops to things like amplifiers is that most amplifiers tend work with fixed gain, and high impedance inputs (such as the signal input to your amplifier) work very effectively as antennas when they are allowed to "float", which is why you can hear whirring and clicking and popping through the speakers the time amplifier loses its "reference" i.e. the signal wire and / or the signal return disconnects itself.

Personally I dislike DIN connectors for reliability in places where they see vibration and / or humidity. You've found the fault in the signal lead with the DIN connector, and because of the way the pins work, once they make a poor connection they're hard to clean up effectively. Depending on the number of pins, playing with the wiring in the back of the plug isn't funny either. I'd replace the assembly if possible.

Good luck with it

Luck indeed! It would appear that it may not be solved after all... I have replaced the DIN with a quality audio one and done some further testing and it appears the lack of sound quality and whiney hissing is back, even playing with the old and new connecter into the amplifier doesn't rectify it anymore. Nor at the head unit. It is back to random, I can shut and lock the car and it be fine or not at all when re opening and driving etc...

Perhaps the Amp or head unit, but I suspect amp, is at fault here as initially thought, which is not the outcome I was really looking for... I am currently trying to try an aftermarket system to see if results and sound varies.

Chasing the DIN lead back through the car, was tedious but achieved eventually and unless something is amiss inside the cable itself. BUT, the new one performs no better now after a few goes of driving and locking and unlocking... Which also makes me wonder if something is shorting said cable or causing damage?

The frustration continues... I will keep you all posted and be back if I find anything with my tester. I am reluctant to replace the amp just yet, if I could even find one. There is still a risk there.

Could be a bad connection in the amp itself, either at the connector, the other side of the connection inside the amp, or at the input circuit stage with a failing component or bad solder joint. This could be on the PCB itself and therefore is an amp fault.

However the electronics are likely to be far more reliable than the connections, there doesn't seem to be a trend on here of faulty amps for their solder joints; and don't lose sight of the fact that it changed behaviour when you moved the lead. If this was at the amp end, I'd concentrate efforts there, wiggling etc. with the new or old lead. It sounds as though you've changed the entirety of the signal lead, does it run the length of the car on the C70?

Is it better or worse with the car warm inside, or having cooled over night?

It could be at the output of the head unit also of course. Audio signals are small before they're amplified to speaker level by the amp, and far more prone to being lost through poor connections.

For your amp, if you have an mp3 player, have you tried injecting a signal into it from the headphone output. There may be a little jiggery pokery connecting it up, keep the volume low to start with (!) but it should give an idea of amp health. I wouldn't try it whilst driving obviously.......

There is no pattern what soever including temperatures. I can see that maybe as some point someone has fiddled with something here and had the amp out, as a result the water pipe from the aerial seems to have been brought up a bit. Enough to allow water to gather below the amp and drainslowly through the plug. It would explain the white powder on the DIN cable and of course it' slightly worn feeling.

I am investigating the amp further, see if any damp has caused damage to the PCB or connectors. Again, even with the new lead it seems better but not fixed or cured... It runs the entire length of the car, bought as a replacement. I also find that playing with an aftermarket unit gives very poor results. Although there doesn't appear to be any hissing or whining the volume is low and very weak, lacking the bass.

Thanks for the input, I think I can safely operate on the amp for the moment and assume that this is the cause. I am likely to say that the head unit is okay. The 3CD has stopped working altogether now, just loads over and over, but I can live without that.

I'll begin operations with MP3 tomorrow and try to finally nail the amp as the cause. If they were cheap and readily available I'd just buy another one at this stage. But we'll see how we get on tomorrow evening.

Hi SeeSeventy,

I held off posting the other day as it seemed as though you were on track for a solution but now I think I'll offer my two-penny's worth!

I am an electronics engineer and have around 20 yrs experience in fault finding of this nature and so I would hope that I can help you get to the bottom of it.

The only sure-fire method for nailing faults like these is to break the problem down into logical sections and test and eliminate each potential candidate.

A reasonable multimeter is essential and it will be a struggle to put this to effective use without a wiring diagram for the system.

I would tend to agree about the amplifier itself being unlikely to be the problem, epecially as you say that the system is still capable of operating correctly at times. Much more likely that the problem is a chafed wire somewhere or a dicky connector. If the wiring can be proved to be ok, you'll have to start to consider eliminating the active stuff like the head unit and amp. As getting hold of substitute units for this is not easy, I'd hammer the wiring first.

One set of readings I would want to take would be across all of the speaker connections where they connect to the amp. Measure for resistance across each speaker channel. Left and right ought to measure similar values for each of the front and rear pairs.

Also measure between every speaker lead and chassis. There should be no path to chassis from any speaker wire. The meter should read over-range on resistance.

Because there is only 12v available in a car, most high powered amplifiers use a 'bridge' configuration for the amplifier outputs and this means that NONE of the speaker connections can be allowed to short to ground. If one is grounding somewhere, the amp will run hot and the sound quality will be diabolical.

Quite unlikely, but still possible, is that one of the speaker connections is touching 12v battery feed somewhere. With the battery disconnected and with the power switch for as many accessories as possible in the 'on' position , measure between every speaker lead and battery +ve. A short here will definitely make the amp feel and sound very poorly.

Any cross-connection of wires from one channel to another will also cause the amp to lose the plot. Again careful checking for shorts is needed.

It seems as though you have done a fair bit to eliminate the signal wiring between the head unit and amp but this should be continuity checked for open-circuit wires, shorts between wires and also unexpected shorts to ground. You will most likely need to 'extend' one of the meter leads and engage the services of a willing assistant for this one. Wiggle wiring as much as possible during each test.

If you can't get a wiring fault to reveal itself and you need to sub in an amp/head, I have a V70 with premium sound. If you're not too far away and our kit is the same (doubtful?), I'd be willing to let you try mine to eliminate yours. I'm in Gloucestershire.

Looking back over all your posts:

1. What is this 'extra' earth you have added at the antenna? I doubt this is related to the problem you're having but still, if there was not a problem with radio reception, why alter the earthing arrangement? You may have added a current path that the designer didn't envisage.

2. What, in your original post, is getting toasty hot?

Anyhow, enough of my rambling, I've got to go to work!

Hope the above gives you some food for thought...

Boots.

Right,

Thanks for the response and added help... I have spent some time almost dismantling the cars interior and going even more in depth.

I operated on the head unit a little to see connections and all were fine. They checked out just fine in my opinion. I once again went through the doors and dash and earths and everything is still top dollar.

Following the DIN down the car that is all good, right up until it meets the amplifier and I THINK I may have solved the issue. Whether it's replacement or repair, I don't know. I will find out tonight.

From what I can gather, someone at some point has removed the amplifier and in doing so, has pulled the drainage pipe from the bung just enough for water to sit in the arch and drain away slowly. I think as a result it's dampened and corroded the connection IN the amp. Even with a new cable it still throws some sound out, not much, but enough to hear. I am dissecting the amp slowly and going to see if it appears as dicky on the inside as it does from the outside.

Thanks for the offer on the lend of yours for testing, I may yet take you up on the offer. Currently outside of Monmouth. However, I am fingers crossed that this will finally nail it with a clean of contacts or clean up with a solder. I had to spend a day cleaning up the hash job of the iPod adapter kit that a previous owner had also put in.

As for the 'other earth' I put it from the aerial as that seemed the only crummy connection, it was also the most prominent sounding thing on the car when the system kicked out. Plus several Volvo technicians and specialists said to try that first as a '20 pence' fix. I've removed it for now, just to make sure that's not interfering.

As for toasty hot! That would be the head unit, I know they can get warm, but this was almost melt your skin off hot. In fact I had to handle it with a cloth, which also got really hot. It seems a little TOO much if you ask me. But the 3CD has stopped working properly, so I could write it off as that.

Thanks again for the help, I will hopefully have a working solution by this evening.....

And a working motor on the passenger seat seeing as I am stripped out as it is!

Update to follow.

You're a bit unlucky if it is within the amp itself and not something less fiddly and external. Opening it up and having look you should be able to see what the state of it is. Amps don't like water as a rule...

It may not be a solder / corrosion issue have a look for any bulging / corroded / leaking capacitors too in the affected area as a damaged one of those (either directly by water or having electricity through it when wet) could be shorting the signal away or going open circuit. Depending on the amplifier design, some sort of capacitor may well be the first thing the signal sees on the way into the amp for electrical de-coupling on the input stage.

I still reckon you're looking as the signal input side, rather than any other part of the amp.

If you have the amp open, remember that although it's fed from a 12V supply, you may well have higher voltages inside the amp - 12V isn't enough voltage for decent volume, so if you change any cappys then observe capacitance and voltage ratings, don't assume 12V will do. I've seen this done......... ;)

Good luck with it, let us know how you get on

SO... I have been a busy boy, inside and outside of work.

BUT, I found the problem. It has been a while, but I was able to dissect the amp and find that there really were some crummy damp connections within the amp itself.

SO, what did I do? I gave it to a specialist to clean up as I was far too busy. Anyway, good news is after a new DIN cable and the clean up repair fo 10 pounds, I am back in business.

Thanks for the direction guys as the car would have been on fire/sold if I hadn't persevered through different avenues. I also hope this helps anyone else who has amplifier issues. I haven't even finished re loading my iPod though, so radio it is for the time being.

I must add that CD player is still playing up and sporadic and there is still some intense heat coming from the head unit itself. I will crack on until it blows up. At least I know it's not the issue for now as I do enjoy the stock look.

C70 amplifier adaptor wiring diagram
 

Hello all I am new here an probably as normal here for help. can anyone supply me with a wiring diagram for the amplifier adaptor 6 pin plug thing so I can put in a after market head unit....
I have managed to get power to my new unit looks pretty an all but I cant for the life of me get any sound. please help.... its driving me mad... thanks in advance...

Or alternatively to cutting... Just buy one of these? Im on my break so in my limited time i only found one coming from the us, but w more time u can find some coming from the uk/eu... I was looking for them when i was thinking of replacing mine but then i bought a box to play my own music as no after market amp will be good enough...

https://www.ebay.co.uk/itm/Volvo-Ste...sAAOSwhQRbQPSS