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Old 10th August 2005, 04:19 PM   #1
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Default Stupid question about testing a Car Radio

I was given a JVC KD-S630 CD Receiver for a car.

I want to test it before installing it, though. It's got a little connector with a bunch of wires sticking out. I plan on using a 12V jump starter we have to test it. It's got a standard cigarette-lighter type 12V plug on it. I want to hook two speakers to it and just throw in a CD and try it. There are three wires - Battery, Accessory and Ground that I know are related to powering it. Ground hooks to ground, and I assume battery hooks to positive, but what about Accessory? Does that also connect to positive?
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Old 10th August 2005, 04:34 PM   #2
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You could use a 12v switching ps rated around 8-10A like a computer atx ps. I have a switching 12v power supply rated 8A, a Mascot type 7805, its 12.6VDC out and i sometimes use it with a inverter to isolate things from the mains.

DONT use a jumpstarter, they are usualy way higher voltage when no load as they are designed to give 12 volts during the starter crank which is around 100-300A in a car.
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Old 10th August 2005, 04:35 PM   #3
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This one has a 12V cigarette lighter plug and I measured it to be exactly 12VDC. I'm not using the jumpstarter part.
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Old 10th August 2005, 04:41 PM   #4
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The battery wire is for stuff like clock, etc. The accessory wire is a switched power wire that only goes on with the car. Connect them both to positive when testing.

P.S. I usually use my computer PSU to test stuff like that. Yellow is +12V, and either black works.
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Old 10th August 2005, 04:44 PM   #5
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If its a car battery charger the radio will just sound like HUUUUMMMMM as there will be no psu caps what so ever. You would need a 10.000F+ capacitor but this will blow up the voltage to 18+ volts and will fry the radio.

And if this unit was given to you i doubt it works. The accessory wire sounds like its a remote to turn on for example a poweramp when you turn the radio on.
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Old 10th August 2005, 05:03 PM   #6
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Well, I was using a car jumpstarter. It's a device with a battery that is charged from a 12V wallwart.

Before testing the radio I checked the voltage of it to be exactly 12VDC, hooked it up, and it worked perfectly!

It's obviously not the greatest, but It's going to go in our boat as a replacement for the even cheaper Audiophase receiver.

It ends up the Battery connects directly to the Positive on the battery, and the Accessory connects to the ignition switch or, for me to test it, directly to the positive as well.
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Old 10th August 2005, 05:32 PM   #7
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Oh its one of those things sorry.
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Old 10th August 2005, 06:44 PM   #8
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the little portable jump starters are just fine. They're really just a 12 volt gel cell in a box. nice and clean ~12 volt power.

The +12v (yellow) wire goes to 12 volts, the ground (black) wire goes to ground. and the ignition/accessory wire (red) goes to 12 volts.

The way it works is that on the amplifier, the yellow wire goes to the battery, and it's always live even when the car is off. The ignition wire goes to iginition switch and is live when the key is in the "on/run" and "acc" positions. The ignition wire doesn't draw much current, and it's only to tell teh car stereo to turn it self on. The stereo draws it's actual operating power from the yellow battery wire. since the batteyr line is also live all the time, it's used to store the radio's memory presets and othe crap.

This is why (when the radio's siwtched on), it'll come on when the car is started or turned to accessory, and shut off again when you shut off the car.

There should also be a blue wire on the radio. This is the remote output line on the radio. This line puts OUT 12 volts whenever the radio is turned on. SO when the radio's on, there is 12 volts OUTPUT on this line untill the radio turns off (either because you pushed the power button on the radio, or you turned the car off). This line is used to tell other car audio equipment like power amplifiers, equalizers/crossovers, and power antennas to turn on. car amplifiers (like what you'd use for a sub) and power antennas also have power ground and turn on lines. You connect their power and ground direct to the battery (always on), and their remote turn on inputs to the blue remote wire on the radio. And whenever the radio is on, the 12 volts signal on that blue wire will tell the car amp to turn on and the antenna to go up.

You should also have 8 wires on that connector for the spekaers. There should be a set of grey ones, white ones, purple ones, and green ones.
white: front left
grey: front right
green: rear left
purple: rear right
The wire with the black stripe goes to the speaker -, the solid ones goes to teh speaker +
Note that unline in home stereos, the _ of the speaker is NPOTat ground, this is a bridged output stage, and both wires sit at about +6 volts. just connect them to the speakers in eh way they should be, and DO NOT LET THEM SHORT to each other or ground, this might blow up the amp chip in the stereo. Despite the lies on the front of the stereo, ALL headunits puts out 10-15 watts (usually enough, get an amp if you want it louder), and not 45 watts a channel. The speaker load is 4 ohms. Most all car speakers are 4 ohms. Only connect one speaker per channel. paralleling two speakers will give a 2 ohm load and blow the amp. do not connect anything less than 4 ohms to teh HU, it will blow. You can use 8 ohms home speakers for testing - it won't blow but won't have as much power.

On some radios, you might also have an "illumination" line (orange I think?). WHenever there is 12 volts on this wire, the front of the car stereo will light up. You can connect this wire to your headlights (if you can get to that signal easily) and make the front of the car stereo light up whenever your lights are on, like a everything else on your dashboard. If you don't, you can just connect it to either the blue remote line to make the radio light up whenever it's on, or to the red ignition line whenever the car is on.

The wire colors I'm talking about are the industry standard for aftermarket car audio; most car sound stuff you cna buy will have these colors, but check first. The function of the wires is usally also marked as well as color coded. Note that the wires in your car WILL NOT BE THE SAME. You can buy little adapters for a few bucks that are basically a connector that fits your car's radio connector with some wires comming out the other end. Basically just match the wires and connect, and then plug in the radio and put it in your dash.
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