Car audio question

Electrical and Ignition

  1. pishta

    pishta I know I'm right....

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    I though we had a few installer here and I wanted to post a question. OG Alpine TDM7534 Head unit: Unit has no ground wire out of the harness so on the bench I hooked a battery charger Neg clamp to chassis and 12V+ to the yellow lead marked ...12V in. Set the charger output to 2A manual and got nothing...I then found an unmarked black wire and used that for a ground (not even on the wiring diagram!) still nothing. I even tried to jump the red ignition power feed to 12V and jack. Any tricks to get one of these lit up on a bench? 15A blade fuse is still intact on yellow power feed but feed goes through a large black box. Is that an RF choke or something? I did get 12V on DMM at the clamps.
     
  2. 71340Duster

    71340Duster FABO Gold Member FABO Gold Member

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    I dunno, seems like you should have lit it up to me. If you are unsure of the black ground lead, you could try doing a resistance check to the metal chassis. If the wire doesn't measure a short to the chassis, maybe try using the chassis for ground, and yellow and red to 12vdc. You wouldn't think anyone would do it this way but maybe they rely on the antenna connector ground. Can you use a sharp test probe and make sure you've got juice on the yellow wire very near where it goes into the chassis? Maybe an internal break or high resistance in your fuse holder, or worse yet and internal fuse. Good luck!
     
  3. RedFish

    RedFish Well-Known Member

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    Typical for DIN head units is red for tuner power hot at switch on, and yellow for memory hot at all times. Sometimes there's a orange for illumination too. A lot of aftermarket head units have a little box inline with these wires going through it. Its a fuse box. Maybe open it and find blown or missing fuse(s).
    I've picked up a few used units over the years and found all those manuals available in .pdf online.
     
  4. Dicer

    Dicer The past is practice. FABO Gold Member

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    I would never use a battery charger to use to check any electrical device, rather it would be a gas gauge or radio or even a head light. Most newer battery chargers will not charge unless it scenes some electrical feed back from what you hook the clamps to. Safety feature built in, if you happen to pull the clamps off of a battery or if they disconnect themselves, you don't worry so much about full current arcing. Batteries take DC current to charge, a cars charging system does an excellent job in doing so using diodes to make a steady stream of DC current. Unforgettably an average battery charger does not produce a steady stream of DC current, it produces a semi-stream of DC current just enough to charge a car battery. Yes you can check this with a meter, and it will show DC current, but using an Oscilloscope you will see indeed it has not a flat signal wave such as a battery. Some electrical devices may or may not check out properly using a battery charger instead of a car battery.
     
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    • TrailBeast

      TrailBeast AKA Mopars4us on Youtube

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      HA!, found it. :D
      It's a slightly different model but they usually use the same wiring for select ranges of models, so this should be right.
      http://static.fixya.com/Manuals/A/Alpine/TDM_7543_E6C85C4CCA548B997D01F79C8F903510.pdf

      That was a tough one to find.
       
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      • pishta

        pishta I know I'm right....

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        Houston, we have a problem....
        This is the harness from the CD DIN jack to the motherboard. Necessary for non CD play? 14870232272741316420441.jpg
        1487023408302-1087626088.jpg
         
      • KitCarlson

        KitCarlson Well-Known Member

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        I can smell that from here. :)
         
      • 71340Duster

        71340Duster FABO Gold Member FABO Gold Member

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        And I was worried about an internal blown fuse....OH BOY!
         
      • superchargeddrt

        superchargeddrt Well-Known Member

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        I used to repair car radios. Sometimes it's necessary to connect the CD player to the din plug as the radio audio is switched internally in the CD player. Sometimes they used to provide a shorting plug that would plug into the din socket when no CD player was present. Does the radio even power up? If it does then there might be a way to figure out which wire's need to be shorted together to make the radio play.
         
      • pishta

        pishta I know I'm right....

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        Well, it looks a little better now. We'll see if it fires up or just fires......had to pull the board out and solder the wires directly to the pins as the plug was fubar. So I'll probe power and ground for continuity before I blast it with 12v again and I think I'll use a battery this time...:) 20170213_195053.jpg
         
      • KitCarlson

        KitCarlson Well-Known Member

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        Nice work!
         
      • 71340Duster

        71340Duster FABO Gold Member FABO Gold Member

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        Yes, nice work indeed!
         
      • pishta

        pishta I know I'm right....

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        Heck yeah, it works! I shot a video of it expecting it to fry that harness again but it powered right up after I hooked the red "ign" lead as posted. Seems the yellow big boy does the constant power while the smaller red lead is the relay power. Interesting feature on this deck is the "interrupt" function of the pink wire. Has something to do with the CD player, like maybe its the 12V signal to tell the deck the changer is powered up or perhaps its the unpublished "aux in" hack that you can do with the DIN cable and some RCA's. And the FFWD/REW is controlled by a 1arge belt circa 1995, that didnt work until I put a rubber band on it as the old belt was flacid.
         
        Last edited: Feb 14, 2017
      • 71340Duster

        71340Duster FABO Gold Member FABO Gold Member

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        Sweet! Any older player is worth saving imo. They just don't make stuff like they used to. Better check that wow and flutter with that belt helper in there tho.....good idea to give it reinforcement. The video was good would have been mushroom cloud good if that clamp would have made it over to the chassis! Good job.
         
      • pishta

        pishta I know I'm right....

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        Yeah, close one. The WOW and flutter is terrible but its not the band...I dont think as it played with its old junk belt, just didnt FFW/REW. Bon Sounds drunk as a skunk...Heck, he probably was! I think it may just need to be lubed as its a gear driven capstan. Also found that the METAL switch was stuck when I put the belt plate back on (you need a toothpick to push switch back when putting plate back on, like a distributor brush) so it doesnt read METAL anymore on Type I-II tapes. Lubed its gears and motor and it sounds fine now. Some strange plastic bracket piece is floating around in there, got to find out where it belongs but everything seems to be working...
         
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