OEM stereo - intermittent loss of Right channel

[Ewan]

hi all - this problem has occurred on and off ever since I put the USA*Spec iPod connector in the car. Originally I just had the iPod and converter box in the boot, in direct replacement of the CD Changer.

Earlier this year, I fitted the box behind the panel behind the seats and ran wiring into the centre console so the iPod is within reach but hidden.

Anyway, the issue is that now and again, the right hand channel goes completely silent - but switching the input to a radio channel on the head unit, the sound comes out of both channels just fine: so it would seem that it's not some fault with the speaker amp in the driver's door.

Whilst listening to the iPod, when this happens it can be sudden (ie halfway through a song it loses the RH channel), and sometimes switching the head unit off and on again will bring it back, sometimes cycling through radio stations & back to CD will bring it back (and sometimes neither trick works until a later point).

The fact that the signal sometimes comes back by switching inputs or by switching the amp off/on again, would indicate that it's not a loose connection per se - it's presumably a fault inside the head unit :(

Has anyone else come across this? Any suggestions of a fix?

thanks,
Ewan

[Sudesh]

I've never used or installed that ipod adapter yet, but from what you described I would have thought the problem was with adapter or the connections.

When you had it connected in the boot was everything working fine?

I assume when you say you put "the box behind the panel behind the seat" that it was on the passenger side and you connected to the OEM CD cable in there?

[Ewan]

That's right, Sudesh, I've put the iPod adapter connected to the OEM CD cable in the panel behind the passenger seat.

When it was in the boot, yes, the intermittent losing channel happened, but it seems to be a lot more frequent now. I wonder how, if there's a simple loose connection, that switching the h/u off and on would restore the connection... If was doing some kind of protocol negotiation, then I could see that breaking and reestablishing the connection, might help - but I'm presuming this is a simple analog connection :dunno:

[Sudesh]

Have to admit I'm a little at loss on this without having the setup to test.

It could simply be the OEM cable to the head unit or the adapter you use.

I think I have a spare OEM CD cable that you can borrow if you what to test that? You could simply plug into the ipod adapter and straight into your head unit and test it for a few day/weeks or what ever it takes to see if the intermittent problem disappears or continues.


That's right, Sudesh, I've put the iPod adapter connected to the OEM CD cable in the panel behind the passenger seat.

When it was in the boot, yes, the intermittent losing channel happened, but it seems to be a lot more frequent now. I wonder how, if there's a simple loose connection, that switching the h/u off and on would restore the connection... If was doing some kind of protocol negotiation, then I could see that breaking and reestablishing the connection, might help - but I'm presuming this is a simple analog connection :dunno:

[Kaz-kzukNA1]

Hi, Ewan.
I don’t have enough samples to backup my opinion and also, each cases that I experienced are somewhat not consistent so please take these into your consideration.

I'm presuming that you have no issues with your Bose AMP at the right door speaker box.

None of the cases below are exactly the same as your issue (no sound from Front Right channel in CD mode) so I could be talking completely unrelated matter.

I haven't measured and compared the current consumption on each circuit tracks (ACC, BATT, PG) behind the CD port inside the audio head unit when it was connected to the OEM Alpine CD changer or to the USA Spec PA11-Hon especially, when the iPod device is at low battery charge.
Having said this and although it seems to be very unlikely, there seems to be a certain condition that results in higer current consumption at the certain circuit track on the board when using PA11-Hon.


Based on the above and following cases, I think you have multiple issues or weak points inside your OEM Alpine head unit and it may got worse by connecting the USA Spec PA11-Hon.


Recently, I was working on JDM NSX and the owner wanted to install PA11-Hon adaptor during the service. Please refer to the recent posts in my Health Check thread for the detail.

When the owner brought his NSX, he told me that from time to time, he got huge noise from FRONT RIGHT door speaker and the only way to stop it was to switch off the head unit. Turning the volume down didn’t stop the noise. Also, the noise happened regardless of the input selection and it happened while listening to the radio or to the CD changer (so bit different from your issue).

Last year, I serviced all three Bose AMPs on this JDM NSX and just as a note, the head unit is also JDM spec.

Initially, I couldn’t re-create the same issue so I replaced the Front Right Door AMP again just in case.

However, after 5 hours of testing, I finally managed to recreate the same issue even with the newly replaced AMP.

In order to be sure, I connected my bench system (another Bose AMP + Bose speaker) directly to the cable at the right side door so that I can eliminate the possibility of issue caused by the speaker.

So, this confirmed that the noise was caused by either the audio head unit or somewhere on the cable from the head unit to the right door speaker box.

The noise seemed to show up when the head unit was warm and it was only from the Front Right channel.

Changing the volume, audio R/L balance, Bass/Treble, radio/cassette/CD input didn’t make any changes to the noise level and the only way to stop the noise was to switch off the head unit.

The noise was like someone scratching the plastic material against the sand paper at slow speed. It was really loud and you don’t want to keep listening to it.

All of these were inspected and tested before installing the PA11-Hon iPod adaptor.

When I finally got the PA11-Hon from US, I first tested it on my NSX and it worked fine. Then, I tested it on this NSX and the head unit didn’t recognise the adaptor as the CD changer. Please note that the owner was using CD changer with this head unit until it arrived at my place so at least, the electrical circuit for the CD port was working at that point.

I had similar issue in the past so I decided to open the head unit.
The capacitors at the bottom circuit board were leaking the acid and damaged several circuit tracks.

While you don’t need the BATT line for the radio and cassette operation, you do need it for the PA11-Hon to be recognised. The leakage from the capacitors damaged or weakened the BATT and/or ACC line to the CD port at the back panel resulting in PA11-Hon not being recognised.

After replacing the capacitors and repairing the damaged circuit tracks, iPod adaptor was recognised properly. I tested the head unit on the bench with the iPod adaptor and it worked fine. Then, installed them back on the car and again, it was fine without any noise.

The owner also tested the system after collecting his NSX from my place and so far, no more noise issue but not many hours were spent so not conclusive.

Please note that this was on JDM audio head unit and the circuit board design was different from the UK spec one.


A while ago, on one of UK NSX, I had similar issue. The owner wanted to have PA11-Hon installed on his NSX.

I tested the owner’s PA11-Hon on my NSX and it worked fine. Then, I connected it on the owner’s NSX inside the boot for a quick check but the head unit didn’t recognise it.

Instead, I got burnt smell of a circuit board. You can find the story on one of the post in my Health Check thread.

When I opened the head unit, although there was no obvious capacitor leakage, the ACC line at the CD port was burnt but still the track itself was conductive.

This means that the capacity of the circuit track was not big/wide enough.
However, it was possible that the ACC line was already damaged in the past on this head unit.

I reinforced the ACC track by adding jumper cable on the circuit board and after that, PA11-Hon worked fine and no more issues.

By the way, there is a dedicated Right audio channel at the CD port so for your case, it sounded like this circuit track for the CD right channel was damaged/weakened somewhere on the board. This explains why you [Edit: don't have issues] when listening to the radio and then you [Edit: loose the right channel audio from time to time] when using the PA11-Hon.


Recently, I worked on UK spec audio head unit.
It completely lost the power and nothing was working when it was delivered to my place. It was similar to the issue that one of the members here reported in the past.

Although this was UK spec audio head unit, it was the same capacitor leakage that I experienced on the JDM NSX above and after replacing the capacitors and repairing the damaged circuit tracks, it recovered its operation. The unit was tested on the bench for many hours using 2 set of Bose AMPs and Speakers for both Front and Rear channels.

The owner seemed to be using his CD changer until he lost the power at the head unit.

I’m expecting this head unit to be at my place again very soon because he experienced new issue.

While the head unit was at my place, he ordered the USA Spec PA11-Hon from US and it was delivered to his place.

The owner installed the head unit by himself after it was repaired at my place.
After this, he listened to the radio and everything was fine.

Then, he installed the PA11-Hon and he found that ‘the right audio channel was not good’.
As the right audio was fine when he was listening to the radio, he thought it was something to do with the PA11-Hon connection.
When he was about to check it, he lost the power completely at the audio head unit.

I think he burnt the circuit track possibly around the CD port.

To avoid any misunderstandings on the possible USA Spec PA11-Hon issue, I have installed PA11-Hon on my JDM NSX a few years ago and I never experienced any issues. As soon as it was installed, the head unit recognised it and it played the MP3 file with no noise [Edit: or no issues] on the right audio channel.

I have been using my NSX (or should I say, JDM head unit) for testing all of the new PA11-Hon adaptor delivered to my place before installing it for other owners and again, no issues were found.

So, based on the above story, I presume, you have capacitor leakage inside your audio head unit.

The leakage may have partially damaged the right audio channel at the CD port. Or, the power line at the CD port was partially damaged by the acid and then weakened the CD right audio circuit track resulting in [Edit: no sound] on the right channel only in CD mode.

Again, I could be completely wrong and the issue may be caused by simple thing....

Kaz

[Silver Surfer]

Kaz, that must be the longest post ever.

SS

[Sudesh]

Kaz, that must be the longest post ever.

SS

lol was just thinking the same! Great info though.

[Kaz-kzukNA1]

Ha ha ha ... It's long but not quite.
Probably, I have even longer one somewhere in my Health Check thread and also, you won't know some of the long-long email that I sent in order to answer the questions from other owners....

Hope, enjoy reading it...

Kaz

[Ewan]

Thanks Kaz, and Sudesh (thanks for the offer of the CD cable - I'll give you a shout if I feel like ripping the interior apart to replace the current one ... but I'm a bit hamfisted so would rather not start yanking panels unless I was pretty confident that it would solve the issue!)

I'll keep an eye on things for now - I'm hoping to have the car over to Kaz next year for the cambelt & water pump service, so maybe I'll ask you to take a look at the head unit when you have it ;-)

regards
Ewan

[Justin]

Anyway, the issue is that now and again, the right hand channel goes completely silent - but switching the input to a radio channel on the head unit, the sound comes out of both channels just fine...

...the signal sometimes comes back by switching inputs or by switching the amp off/on again

Ewan - Are you saying that the channel is always restored when you switch inputs on the hu, or only after cycling through a bit? Because if it's always rectified immediately, I'd be checking it's definitely not just the 30 pin connector at the iPod? These can fail either at the iPod or at the connecting plug. It might be worth swapping out a different pod in the first instance?

And stupid as it sounds, remember that iPods run a miniature little o/s and genuinely do respond well to that old IT chestnut of rebooting, checking firmware, blah blah blah....

Anyway, if the right channel issue is only ever present at the iPod input, I'd be concentrating the search between the IPod and PA11-HON inclusive.

[Ewan]

hi Justin

Basically, what happens is:

* playing iPod, periodically the RH channel disappears almost entirely (switching the balance to R and cranking up the volume, I can hear something - dunno if it's the actual signal for the R channel or some kind of bleed from the L channel, but coming out from the R speaker).
- sometimes it comes and goes on its own - ie just as it disappeared, it comes back
- switching the HU off and on again sometimes brings it back - maybe once in each 3 or 4 attempts
- ditto, cycling through radio freqs and back to CD (but without exception, when I switch to radio, the sound comes out of the R speaker again)

So with all that, I'm inclined to think it could be the iPod, or the connecting cable between the iPod and the adapter, it could be the adapter, or any of the cabling between it and the HU, or it could be the HU itself (as Kaz has suggested).

Maybe I'll try another iPod and see if that works out :)

cheers
Ewan

[Justin]

without exception, when I switch to radio, the sound comes out of the R speaker again)


I'm definitely inclined to think that your issue is happening before the signal hits the back of the hu. Should be easy enough to check:

1. Swap out the iPod (to eliminate iPod fault). If not fixed:
2. Reconnect your 6-disc (to eliminate PA11 fault). If not fixed:
3. You begin to start thinking hu...

Don't think it can be anything forward (speaker-side) of the hu if the sound is always restored on changing hu input selection.

Finally, an alternate to 1&2 might be to connect your iPod and PA11 to another car if that's an easier proposition, and see if the fault is replicable.

Good luck anyway Ewan, these sorts of fault can be super annoying!

[Hagasan]

Hi Ewan,

only quickly skimmed the top of this thread and what I am about to suggest may have been said.......

as the iPod is mimicking a CD player using the CD cable.....Have you tried putting the CD player back in? I don't know if there are different signal levels between the CD player and the iPod adaptor. It would help determine whether it's the "cars" equipment of the iPod stuff. Another iPod is worth ago but still leaves the adaptor in question if the fault persists....

Gary

[NSX 2000]

I'm definitely inclined to think that your issue is happening before the signal hits the back of the hu. Should be easy enough to check:

1. Swap out the iPod (to eliminate iPod fault). If not fixed:
2. Reconnect your 6-disc (to eliminate PA11 fault). If not fixed:
3. You begin to start thinking hu...

Don't think it can be anything forward (speaker-side) of the hu if the sound is always restored on changing hu input selection.

Finally, an alternate to 1&2 might be to connect your iPod and PA11 to another car if that's an easier proposition, and see if the fault is replicable.

Good luck anyway Ewan, these sorts of fault can be super annoying!


Hi Ewan,

only quickly skimmed the top of this thread and what I am about to suggest may have been said.......

as the iPod is mimicking a CD player using the CD cable.....Have you tried putting the CD player back in? I don't know if there are different signal levels between the CD player and the iPod adaptor. It would help determine whether it's the "cars" equipment of the iPod stuff. Another iPod is worth ago but still leaves the adaptor in question if the fault persists....

Gary

I would agre with the above posts. I can bring an Ipod on Thursday, plus you can try your ipod and adaptor in my car if you want.

Paul

[Ewan]

Thanks guys - I'll maybe have a shot of Paul's iPod on Thurs. Trouble with things like this is, due to their intermittent nature, it's not easy to be sure it's fixed with a quick try :)

rgds
Ewan

[Ewan]

I finally got around to sorting this out today :)

Removed all the interior panels where the iPod adapter was installed and it seems there's a loose connection in the cable that connects from the adapter to the factory stereo (ie I have it connected to the CD cable behind the passenger seat). I rerouted the cabling and so far, it seems to be fine... touch wood!

Anyway, I had bought a replacement PA11-Hon adapter when in the States recently (along with a suitcase full of bits for a Kaz TB service), which is now surplus to requirements. If anyone reading this has a stock BOSE stereo and fancies it, look here (http://www.nsxcb.co.uk/showthread.php?8841-FS-USA-Spec-PA11-Hon-iPod-adapter&p=82342#post82342).