I figured I might just put a little thing together in this section to help out some in need of understanding some basic electricty things that are common to all automotive audio applications...... First off (pardon me those of you who know this like the backs of your hands...and I am not gonna delve into the electron therory of power flow that runs negative to positive, just basic stuff...) Let me give an example of the most basic circuit in 12v automotive....a light bulb.... In this circuit you need to have (as in every circuit) three basic things.. 1. battery 2. conductors (wires) 3. load (the light bulb) Current flows out of the battery from the positive post, through the wire, into the light bulb, through the filiment, then out of the light bulb through the wire back to the battery and you have a complete circuit....Since the light bulb is the only load in the circuit, it uses all voltage available....if there were two light bulbs (wired in series) each would use half of the load ( 6 volts each)...After the last load in the circuit, the wire leading back to the battery (ground) should have no measured voltage in it.... So if we were gonna use a volt meter and check some things, here is what we should find where....Across the battery we should have 12 volts....If we keep the black meter lead on bat. neg. and put the red lead just in front of the light bulb, we will read 12 volts....on the other side of the light bulb (if the bulb is good and lit) we would read what voltage there?....ZERO... If we read ANY voltage after the light bulb what does this tell you??? It tells you that from that point to the battery neg. there is another load. Now if you have a bad connection or corrosion in that wire, it is going to act as resistance (a load) in the circuit..... So let's plug in a car audio circuit and apply the principals.....Let's say it is the wiring of a single amplifier.....We measure battery voltage at the battery and have 12 volts....if we leave the black meter lead on bat. negative and move the red lead to the amp positive power terminal and our reading is 10 volts, what does that tell you? it tells you that between the battery and the amp, there is another load...if this wire is direct from the battery to the amp it should read the same voltage as the battery....A bad connection or corrosion is likely to cause this voltage drop...If you move the red lead to the negative terminal on the amp, it should read zero.....if it has any voltage in it, that will indicate a bad ground (connection, corrosion, etc..) Most times the amp is grounded to the chassis or body of the vehicle....The chassis and body are basically just huge ground wires so wherever there is a ground cable or strap from the battery to the chassis it just allows the chassis to be connected to battery negative...Sometimes the battery ground is a single cable that connects to the engine and then the engine may have points to connect to the chassis....All of these places are places to look for bad connections if you read voltage on the ground circuit..If your car has no direct connection from battery to chassis (ground), it is a good idea to install one just to make sure of a good chassis ground...Unless you put a wiring harness in yourself to run your audio grounds back to the battery direct, all of your audio components will ground to the chassis (bad grounds at these places can be the source of noise in the audio system) and depend on the chassis being properly grounded..... Hopefully this will give you a little knowledge about how to check for actual power and grounds in your audio circuits.... thanks Willy
thanks, willy.. you might need to save that link, though.. it seems no matter how thorough we are about putting good information here, people are too lazy to actually search for it.. They'd rather register and then start asking questions.. (which is wonderful)- But like I said.. keep the link handy.. you'll probably need it.
If your car has no direct connection from battery to chassis (ground), it is a good idea to install one just to make sure of a good chassis ground... Excellent point there, Willy. Case in point. I volt dropped my positive from battery post (Not terminal) to positive amp connection at 2/3 volume. .3 volts, which I felt was decent considering the length of cable. I neglected to drop the ground side. Heck, my ground cable is less than a foot long, was cleaned to bare metal, all the right stuff. After reading this forum for a bit, it was stated to take care of the big 3. Little did I realize that my ground was basically junk. 1.6 volt drop at the same volume on ground side. Well, I have a big ol cable coming of my negative. Straight to the engine. I neglected to take into account the 14 gauge wire from the negative to the body. 4 Gauge to that with quality terminals that accept proper cable gauge, tinned wires, tinned connections, and it went to .2 voltage drop from negative post to amp ground. Sad thing is, I knew better. But, we still learn, right? Hmmmm Conventional Theory vs Electron Theory. Long as my amps turn on, I am good with either.
Right. Learning is one of those on going processes. I learn everyday. And just think there are many that will never learn. So we are definately one up on them.
