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SC-901 Pro Logic Sound Issues

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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SC-901 Pro Logic Sound Issues

Post by subzerocarfanatic » Wed Jun 24, 2020 4:05 pm

I want to know if anyone else has had this problem and a solution to fix it.
When I select the Pro Logic option it sounds awesome when it works but most of the time it cuts out to bad like half the speakers quit producing sound,only does this on the Pro Logic option.Still have not got the CD player to work,it loads the disc it sounds like then unloads it or something and tries to keep reloading over and over but it will not play.I did clean sensor with Q tip and alcohol. Any suggestions on either problem appreciated!
Chris

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Re: SC-901 Pro Logic Sound Issues

Post by scot850 » Wed Jun 24, 2020 4:45 pm

The SC-901 is finicky. What is happening to the CD is the laser is not seeing the discs so 'hunts' for one.

There was a thread on this a week or so ago for that issue. There is a how to on the interwebs for how to clean that correctly, but make sure you clean the laser head with IPA first and then again with a dry cotton bud to make sure it does not leave a film on the surface.

Pro-Logic - Do you have the middle speaker? Could be it is bad or the processor has been wet and gone bad. LAst option again is a wiring issue with a broken wire or connector.

Neil.
2000 V70 R - still being an endless PITA
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1997 Volvo 850 SE NA - Went to niece in California - Sold
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Re: SC-901 Pro Logic Sound Issues

Post by RickHaleParker » Thu Jun 25, 2020 4:32 am

Check and clean the Pro logic decoder connector on the back of the SC-901 head. The decoder is a separate unit. It is not built into the head. While you are at it do the same for the connector to the Amp.
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Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
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Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0.
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Re: SC-901 Pro Logic Sound Issues

Post by subzerocarfanatic » Thu Jun 25, 2020 6:49 am

RickHaleParker wrote:
Thu Jun 25, 2020 4:32 am
Check and clean the Pro logic decoder connector on the back of the SC-901 head. The decoder is a separate unit. It is not built into the head. While you are at it do the same for the connector to the Amp.
The amp that is mounted in the trunk driver side fender well area?

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Re: SC-901 Pro Logic Sound Issues

Post by RickHaleParker » Thu Jun 25, 2020 8:31 am

subzerocarfanatic wrote:
Thu Jun 25, 2020 6:49 am
The amp that is mounted in the trunk driver side fender well area?

Not the Audio amplifier, the Dolby Pro Logic decoder. Which is under the dash behind the SC-901 head then down on the tunnel. It plugs into the back of the SC-901 head.

Your Dolby is cutting out not the Audio amplifier.

The amp is mounted on the back side of the bracket for the 6 CD changer which is right there where the side pocket is.
You remove the lower half of the side pocket when you install a CD changer in a C70. That is how you get access to change the CDs. The power connector and the DIN cable for the CD changer is there also.

Dolby Pro Logic decoder location.
2020-06-25.png

Audio amplifier and CD Changer location.
IMAG0020.jpg
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Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000.
Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0.
Platform P2 2004 S60R, B2524T4, AW50/51 AWD, B8444S TF80 AWD, Bosch Motronic 7.0, BorgWarner K24 turbocharger. V8 conversion in progress.

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Re: SC-901 Pro Logic Sound Issues

Post by BEJinFbk » Thu Jun 25, 2020 12:58 pm

RickHaleParker wrote:
Thu Jun 25, 2020 4:32 am
Check and clean the Pro logic decoder connector on the back of the SC-901 head. The decoder is a separate unit. It is not built into the head. While you are at it do the same for the connector to the Amp.
+1
Pop the radio out and unplug then reseat
the Dolby DIN connector a couple of times.
Hopefully, it’s just dirty connector pins.
'98 V70 R - Well Equipped for Life Up North... ;)

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