Archive for the ‘Electronics’ Category

My dad bought this old Holden ute for us to bush bash around in at our farm. But me and my quest for experience couldn’t see this as anything less than a perfect opportunity to get some car audio experience, before this all I’d done is put a new head unit in my own car which was a simple remove dash, pull out old unit, cut off wires and attach wires for new unit job.

The ute however, started like this:

It didn’t matter how hard I tried, I just couldn’t get the Bluetooth working! And the fact that the speakers had been removed from the doors didn’t help either.

So I decided everything needed to be replaced. I went down to Jaycar and picked up a cheap head unit with radio and MP3 input and a pair of 6″ drivers to work with.

First part of the job was to remove the old unit. This required tedious screw removal from the glove box and under side of the dash to get it off, and eventually I figured out to get the unit itself out I had to unscrew the knobs on either side. After that I decided to just cut all the wires as it would be safer and easier to redo it.

To make things more difficult this units hole was smaller than the new unit. So after some awkward angle grinding, eventually I got the size to what was needed, and inserted the head unit frame.

Next was the speakers, this was a pretty simple put them in the hole and screw them in process, then I ran the wires through the doors, behind the floor mat and around to where the unit was.

Then comes the fun part, wiring. First I wired up the positives and negatives for the 2 speakers to get them out of the way, then I could concentrate on the power. My original plan was to wire both the ACC and the Battery wires straight to the car battery, but a friend of my dads showed me I could wire it straight into the fuse box. We tested what fuses were there to find one that would give constant power without a key in the ignition and one that would only give power when the key was on accessory, which meant I could set it up like a normal car head unit! So we pulled out the 2 fuses and stuffed the end of the Battery wire under the fuse without the constant stream and the accessory wire under the one with the constant stream.

*Blue – Battery Wire

*Red – Accessory Wire

Then all that was left to do was tape up the wires to the wires coming out of the attachment for the back of the uni…

Plug the attachment into the unit, plug in the antenna cable, slide the unit into the frame and put the underside of the dash back on!

And that was my super old car audio makeover!

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Our lecture talked about the different dBs today and their common levels, 0 dBm being 1 mw in a matched 600 ohm load circuit creating .775v, +4 dBm being a 1.228v circuit for a stronger signal, meaning you have to pull your VU meters back so they’re not always maxed out, +4 dBu being a 1.228v signal in an unloaded circuit and finally -10dBV, a 1v signal regardless of impedance, reduced by 10dB, generally used by all consumer electronics.