My 2004 C70 SC-901 whines when in Pro Logic mode only. Not alternator noise, happens when engine is on or off. Any ideas?

 

Could be a ground loop? Have you had any electrical work done on your car recently? Anything "aftermarket" added? GPS, Satellite Radio, Hands Free devices, Power Inverters?

 

Talked to the Alpine Service Center (URS). The tech there and I both are pretty sure its the radio... Ive already pulled it out and sent it in for an estimate.

 

OK, the tech rep at URS (the alpine service center) got my head unit today and he cant replicate my problem. He says he called Alpine and they say that the issue is likely in the amp or in an equalizer somewhere. Since the units equalizer is built in, Im guessing it must be a problem with the amp. I found one on ebay that I purchaced but I wonder if anyone has any experience replacing or having an amp worked on? The URS tech says the amp is not Alpine and they dont know if it is servicable or not.

 

I've never had one "fixed" before. Which is to say that I've had two sent in (non Volvo) but neither came back fixed. I've had luck replacing them before. If you already have the 901 out of the dash, replacing it shouldn't be too hard.

Did I read correctly in another post of yours that you were thinking about adding a satellite radio?

 

I found a used amp on ebay. The C70 amp goes in the trunk. If anyone is interested, Ill post my results. As for satellite, Ive decided to go with a refurbed Sportster 4 with a sirius FM modulator. The modulator is a simple plug and play item with no extra power to connect and it cuts out the cars antenna when the Sirius is on. It gets excellent reviews, not quite digital but close enough for Howard Stern. The Sportster 4 docking station has a stereo miniplug Aux In that will allow me to plug any brand MP3 player in and play through the FM Modulator. Its a nice clean inexpensive install that should hide well in the space under the ashtray and not require removing everytime I park the car on a city street.

Sportster 4
http://shop.sirius.com/edealinv/serv...ParentID=42826

FM Modulator
http://shop.sirius.com/edealinv/serv...p;oldParentID=

I shopped em pretty hard and it all comes to the house for less than 65 bucks.

 

Ok, I see what you did. That's decent little setup! If it works....it works, eh?

So, does this whine reproduce itself when you're not using the satellite radio? Or at this point, is the whine persistent with everything (in pro logic)?

 

Ive ordered all the pieces, havent installed yet. The whine is internal to the system. Im replacing the amp next to see if thats the issue, Alpine seems to think it is. The SC901 checked out fine at the service center.

 

Well, good luck with it. I guess I'd still check your grounding before you replace anything. 9 times out of 10, background noise is grounding related.

 

Maybe I should clarify. The URS tech says that he called Alpine and the Alpine tech is the one that says the noise is likely not coming from the head unit but from either the amplifier or "from a seperate equalizer or something" Since the noise is only in the prologic mode, it may be the dolby unit. Where is the dolby processing unit? Id like to check the grounding of that unit.

 

sorry...I should also clarify...I was talking about the grounding on the amp.

I would have thought the dolby processing unit was inside the HU. Most aftermarket applications have the channels split out right before it goes to the internal amp of the HU. I don't see why an OEM unit would be any different. Unless the amp in question is 5.1 or 6.1.....In any case, you'll have to crack it open. I have no idea what it might look like.

 

Next update. I found a link where a guy had pulled his dolby pro-logic unit and found some soldering problems. I pulled the prologic unit out today and took a peek inside. Not sure if its the problem but I did find one capacitor that had given out its electrolyte... or so my Electrical Engineer cousin said after I described to him what I saw on the board. He builds stuff like this for a living so Im sending it to him to replace the cap... will let you know if anyone is interested.

 

Did you ever get this issue resolved? I have the same issue...it's intermittent but when it's active it's unlistenable because of the volume of the whine. I was told by the Volvo service guy that I would probably have to replace the Pro-logic module, but I wanted to see if you ever got it fixed and what did it if you did. Thanks.