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Thread: Stereo not working

  1. #1
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    Stereo not working

    Just aquired a 90 SC that need some tidying up. To start with the radio was not working. After taking it out
    I saw that all speaker wires were cut off so I cut the wires off a working T-bird (LX) to get the clip and soldered all together but, nothing.
    Radio illuminates and it select stations but no sound is comming out of the speakers and the CD changer is not working (it
    worked in the other car so the head unit is OK). Where do I start? Is there an amplifier, like in the mustangs, that need power?
    I hate to draw new speaker wires to the door and fit an aftermarket unit if I don't have to. Tips welcome.

  2. #2
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    The headunits/CD players seem to go south quite often given their age, and w/the JBL Premium system there are two amps in the trunk - if you want to stay stock, your choices are repair of OE, or replace w/used - see this link for tips on wiring, etc. and on the topic of repairs: http://www.35thatr.org/Radio/RadioRelatedPages.htm

    I have a spare CD player I took out of my '90 when I got it P/N E91F-19B160-AB, condition unknown, as there was a Ford non-SC head unit in my car when I got it. I've since replaced everything but the speaker wiring, power circuits, and power antenna.

    About the speaker wiring, Scosche sells a jumper harness that allows you to keep the factory wires when deleting the stock amps, so not a lot of concern about having to pull new. There are also aftermarket adapter harnesses for connecting aftermarket headunits to the factory radio/speaker harness in the dash. Heads up, there is not a lot of room behind the headunit for extra wiring.

    One more thing about wiring - w/these cars, a factory EVTM is your best friend...check eBay where they are often fairly priced.
    Last edited by KMT; 08-04-2019 at 01:46 PM.

  3. #3
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    There is a wiring block in the passenger kick panel that is for all the speakers plus there is a bypass block in the trunk where the subwoofer can be bypassed as well. Schematic pics attached.

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  4. #4
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    Using a '90 SC as an example, note the bottom right of the last diagram does not show the red/blk power/gnd. connector at the actual sub amp.
    Last edited by KMT; 08-05-2019 at 10:29 AM.

  5. #5
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    Truth be told this is a 1993 schematic that came with my 93/94/95 CD. The 90 and the 93 should be *similar* which is why I chose to share the images.

  6. #6
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    Quote Originally Posted by potshotscott View Post
    The 90 and the 93 should be *similar* ...
    130-3/130-4 in my '90 EVTM has slightly different diagrams, and shows the red/black. Only reason I mention it is because I'm knee deep in the JBL w/CD wiring on my Anny at the moment. Had to go to my spare parts to confirm at the amp itself to be sure where those wires were actually used.

  7. #7
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    Does anyone know of a person / facility that still repairs our radios? The last one I found on this site did not respond to my email inquiry.

  8. #8
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    Quote Originally Posted by RS2600 View Post
    Just aquired a 90 SC that need some tidying up. To start with the radio was not working. After taking it out
    I saw that all speaker wires were cut off so I cut the wires off a working T-bird (LX) to get the clip and soldered all together but, nothing.
    Radio illuminates and it select stations but no sound is comming out of the speakers and the CD changer is not working (it
    worked in the other car so the head unit is OK). Where do I start? Is there an amplifier, like in the mustangs, that need power?
    I hate to draw new speaker wires to the door and fit an aftermarket unit if I don't have to. Tips welcome.
    I suspect the amplifier doesn't get any power but where is it located? Radio get power but that's about it

  9. #9
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    What was state of the art then isn't now. I have replaced all my factory systems with aftermarket units for the quality of sound, bluetooth, pandora etc all for less than trying to repair an original headunit. The factory amps are under the rear package tray
    and rarely go bad so if you get a new head unit and speakers that are relatively easy to install you'll have better sound with all the convenience of up to date units for a couple of hundred bucks.
    Last edited by fstcoup; 08-25-2019 at 01:35 PM.

  10. #10
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    Quote Originally Posted by fstcoup View Post
    What was state of the art then isn't now. I have replaced all my factory systems with aftermarket units for the quality of sound, bluetooth, pandora etc all for less than trying to repair an original headunit. The factory amps are under the rear package tray
    and rarely go bad so if you get a new head unit and speakers that are relatively easy to install you'll have better sound with all the convenience of up to date units for a couple of hundred bucks.
    From what I understand, all speaker wires goes from the head unit to the main amp and then to the speakers so if the amp is not working there will be no sound comming from the speakers. Am I correct?

  11. #11
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    Quote Originally Posted by RS2600 View Post
    Am I correct?
    Right. No amp(s), no sound.

    And i agree, the head unit is usually the issue. The amps can't output to the speakers if they don't get inputs to start with.
    Last edited by KMT; 08-25-2019 at 04:30 PM.

  12. #12
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    Quote Originally Posted by KMT View Post
    Right. No amp(s), no sound.

    And i agree, the head unit is usually the issue. The amps can't output to the speakers if they don't get inputs to start with.
    The headunit is not the issue, took it from a 93 Bird in working condition. Is the main amp really located in the trunk? Find it stange that
    all speaker wires is routed to the rear and then back again to the doors. I know the sub amp is in the trunk but there should be another somewhere.

  13. #13
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    Quote Originally Posted by RS2600 View Post
    The headunit is not the issue, took it from a 93 Bird in working condition. Is the main amp really located in the trunk? Find it stange that
    all speaker wires is routed to the rear and then back again to the doors. I know the sub amp is in the trunk but there should be another somewhere.
    1) Somewhere around 1993 they changed the AMP_ON voltage from 12V (early radios) to 5V; so a later head unit won't turn on the older amps UNLESS you swap the ANT and AMP_ON wires at the connector (and remember to swap back later!)

    2) Yes, they ran them that way. The speaker amp (on non-JBL) and satellite amp (on JBL) is on the passenger end of the package tray.

    RwP

  14. #14
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    Quote Originally Posted by RS2600 View Post
    The headunit is not the issue, took it from a 93 Bird in working condition.
    Just because it works doesn't mean it can't be a possible issue contributing to your current efforts And when I say the headunits are usually the problem, I'm only talking about early JBL system series, not later or units from other models. Meaning I doubt that in your example there is an outright fail w/either of your amps. They can be fine, yet offline due to external problems.

    If they are kept in use as part of a hybridized setup, all bets are off when it comes to stock wiring, etc., but I'm sure that they could still be used in some examples. As I said, I opted to not use them when I moved to a modern head unit. If you want only plug/play, my advice is to source a working direct replacement headunit...if you can, but that comes back around to them all being subject to the same issues. All of this has been known to the community for some time. I can understand wanting a simple out/trying to keep things as stock as possible, but if there were a simple solution/replacement, I think it would be already documented and this thread wouldn't be needed. The fact that someone created a cottage industry out of repairing the early units should be a red flag.

    When it comes to powering up the amps (trunk/package tray), they have both turn-on and power wires. Power is red (black ground) and turn on is a thinner yellow. The yellow is in a bundle w/the speaker wires and the power/ground is separate. The turn-on signal is off the headunit so it is output only when it is on. Power is always hot when key is on. I'd grab a meter and confirm what's going on with those wires in the trunk with the radio and key both on.

    If as ralph notes the '93 head unit isn't feeding the turn-on signal properly, it won't matter if the power wires are hot, so...

    And as a reminder, since you're working on a '90 w/JBL, the diagrams above are for a '93, so be aware of any differences, etc.
    Last edited by KMT; 08-26-2019 at 10:47 AM.

  15. #15
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    Just to add to the confusion, I think a faulty cd player will cause a head unit to produce no sound. I think the head units w/o the slave cd had a jumper plug on the back of them.

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