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Loud Audio Blowing Accessory Fuse (Remote Wire)

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  • Loud Audio Blowing Accessory Fuse (Remote Wire)

    Quick overview of my setup:
    Sony 600w 4 channel amp hooked via 8 gauge wire
    Remote wire hooked up to the accessory line of the radio harness
    Netbook feeds audio signal to amp via usb 7.1 soundcard
    MiniTouch 700 powered off of same accessory line as the remote wire

    The issue:
    After lots of tuning and testing today, I opened and Centrafuse and it started to play some music rather loud (likely at max volume). After a half second or so the monitor and audio cut out. Clearly it was a fuse. What doesn't make sense is why the fuse that the remote wire is on would trip. Is there some other way I should be connecting the remote wire to switched 12v? I highly doubt it has anything to do with the monitor having too high of a draw. The only new pieces I've had in the past month are an usb obd2 scanner and the laptop auto-start circuit that can be found on the boards here. I went over the system several times on the bench before moving it to the car with the amp, and didn't find any shorts and had no issue running the monitor and auto-start circuit off of one 12v molex connection. With that in mind, I can only look at the remote line as being the culprit. Suggestions for correction?

  • #2
    I would start by putting an ammeter in each line (one at a time: monitor, remote trigger, etc.) and see what the current draw of each of component is. That should give you an idea as to what should be relayed or if the amp has an issue. If the blowing of the fuse is related to volume, there has to be some kind of a problem with the amp.
    My 2007 Ford F350 Work Log located HERE

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    • #3
      Not sure if my little multimeter can handle the amperage (I think it only goes up to 600mA) that something on the circuit is drawing. The screen is rated at < 9w/1 amp, and from what I've read, the remote wire should only be pulling half an amp max. I still find it hard to believe that the small circuit I put in for the auto-power on http://www.mp3car.com/user-innovatio...module-37.html could be drawing over 6 amps. Seems like the components would melt before that could happen. The amp is a fairly new (few month old) Sony 600w 4-channel, if that makes any difference.

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      • #4
        Many inexpensive meters have a 10A shunt in them to measure up to 10amps just by moving the red lead over to the shunt plugin. I'm not sure how you will identify what to do otherwise unless you decide not to worry about what if drawing all the power and just add a relay to the main power line feeding amp and trigger it off of the acc. wire
        My 2007 Ford F350 Work Log located HERE

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        • #5
          Insert a lamp or headlamp in series.
          If a headlamp lights appreciably, you know that circuit is drawing several amps (55W headlamp = ~4.5A; 100W =~8A).

          Else with a 10A DMM, keep the volume low and gradually turn it up to a max of (say) 8A.

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          • #6
            So, I bought a better meter. My screen and auto-on circuit draw less than a 5th of an amp at peak. The amp remote wire was peaking at 3 amps at a quarter volume. Why would the remote wire have a variance in current draw at all? How can I limit the current draw?

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            • #7
              I suspected thats what you would find. I guess the trigger circuit is not properly isolated from the main power feed in the amp. I hate to say it but I really really hate Sony audio equipment. Can you imagine if you had hooked that amp to a headunit remote wire that is usually limited to under 500mA output? Anyways, if it were me, I would try to ditch the amp and replace with any other brand. The other option is relay that wire to the main feed circuit and feed the relay off of the acc. circuit as you are doing now.
              My 2007 Ford F350 Work Log located HERE

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              • #8
                I figured buying a cheap amp would bite me in the long run. What brand would you recommend? I guess I could bump up to a 5 channel while I'm at it. Short term, would a standard automotive relay suffice?

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                • #9
                  Automotive relay should be fine, they are usually good for 30amps.

                  as far as amp brands, any of the big players should be fine: Pioneer, Alpine, Kenwood etc. I've had good luck just buying used off of craigslsit or similar. One of my Infinites I bought new, the other I bought used, no issue with either. The only thing I hesititate to buy used is speakers, especially subs, they can be badly abused but still look fine on the outside.
                  My 2007 Ford F350 Work Log located HERE

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                  • #10
                    You could also try the12volt.com, they have good audio experience.

                    I agree that a remote wire should only ever be low current, usually mA for a sensing circuit and at worst the current that the internal relay draws (ie, usually way under under 1A).
                    And that the remote current varies will output etc... wtf?


                    Funny, I like Sony - but that's for domestic stuff, and one pair of car speakers.
                    Car-wise, I'm going back to Alpine HUs.

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                    • #11
                      You guys may find this amusing:

                      Went out last night and grabbed a relay and a 15 amp auto-reset circuit breaker. Wired it all up, tried it out, and it worked great. I thought to myself "finally have all the main systems working again, great." This morning, I turned on my car, PC came out of hibernate, usb audo initialized, nice loud POP, and then....no audio.

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                      • #12
                        No, I hate to hear when sh.. blows up. I assume it was the amp finally giving into what ever circuit gremlins were going on inside? Or something wrong in the sound card or what? If it was the amp, look at the bright side; you put it out of it's misery (and yours) so you can move on. I could tell you story after story of fighting with Sony stuff to get it to work right. I have a Sony TV and I will say they have the video side of things dialed in, they should just stay out of the audio market (home and mobile) IMO.
                        My 2007 Ford F350 Work Log located HERE

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                        • #13
                          If it is completely dead, a post-mortem will be fun. I'd like to know what the root cause was; seems like a bizarre way to fail.

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                          • #14
                            So, it turns out putting that 15 amp auto-resetting circuit breaker was a good idea. The usb initialization "thump" apparently causes the amplifier to pull over 15 amps. If I start the car and allow the PC to resume, then turn the car off and on again (resetting the circuit breaker), I have audio.

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                            • #15
                              It's still not right though, that amp should never pull that kind of current through the remote turn on line.
                              My 2007 Ford F350 Work Log located HERE

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