Radio Help- Installing an Aux Port

[Baskinator]

I saw this done on the AMC forum and was wondering if anyone would like to help me put an aux line in my Eagle's stock AM/FM stereo. It is the dual knob radio, and I assume it wouldn't be too difficult since it's not mono sound.

By aux port, I'm talking about a line between the stereo and volume control that can be switched manually to take an audio feed from an mp3 player. This would allow use of an mp3 player while still retaining the stock radio functions if desired.

I can supply pictures of my radio internals if needed, and it would be wonderful if someone could draw something up. I'm certainly no electrical/audio engineer, but I can take directions to perform simple wiring and soldering.

IIRC, there is potential for electrical problems/fire if done incorrectly, and there may be problems with charging the mp3 player in the lighter port while plugged in. It would be important to address these things as well. I hold myself responsible for anything I do to my own vehicle and am very cautious in my work, so don't be afraid to offer your knowledge!

[vangremlin]

have you thought about putting a radio frequency modulator in between the antenna and the radio, which would allow you to tune your radio to a pre-selected station and receive the output from the mp3 player?  I've done that on a couple vehicles, including my Eagle.  Let me know if you'd like more info.

[Baskinator]

I've seen those before. No offense, but they're rather expensive and don't perform much better than the fm transmitters you can plug in to the ipod. They often get interrupted in urban areas and have to turn the digital signal into an analog one, decreasing sound quality. Considering I already don't get the best signal to my radio, the sound would most likely be very poor quality. I also drive > 2 hours between school and home often, so I would have a similar problem of having to change the station to adjust it frequently. More trouble than it's worth.

I would much rather have an actual switchable aux port and spend under $10 if I can. I'd also really like to know how easy or difficult this could be, and possibly put together a write-up for other people to use. If I don't get any takers, I might just attempt it myself.

I have another dual knob radio with a cassette player that I was going to install, which I could use one of my many cassette adapters for. Adding an aux port would allow me to keep the stock radio (instead of having to figure out the odd wiring) and be the most convenient option.

Here is the link to the one added to a Rambler Radio: http://theamcforum.com/forum/mp3-player-with-old-radio-one-solution_topic16338.html

[amcinstaller]

so why cant you just follow the writeup that you just linked to?

[Baskinator]

Like I said, I'm no electrical/audio engineer. That "writeup" is very technical and has no pictures of the actual install. Even if it did, it's a totally different radio and theirs is mono. I may be able to figure it out eventually on my own, it would just take me much longer. I'd rather not risk destroying my radio if someone is willing to help, but otherwise I'm not entirely worried. I'm in the process of changing it anyway, but this would be easier and more gratifying.

My radio bezel has been off for a while as I ponder the options, so it's a matter of just unhooking the connectors to get at it. I have no concerns with taking it apart as I've worked with many computers before.

I'd be very grateful if someone with the know-how could take a look at that page and interpret it for an Eagle application. Thanks!

[Baskinator]

So I found an instructable from one of the members that responded to that post and it seems like it may be pretty simple after all. I just need to head to radioshack and pick up an input jack to wire in. I'll keep ya posted!

[vangremlin]

No offense, but they're rather expensive and don't perform much better than the fm transmitters you can plug in to the ipod. They often get interrupted in urban areas and have to turn the digital signal into an analog one, decreasing sound quality.

Okay, glad to know this is something you've already looked into.  Good luck with the project!

[Baskinator]

My panel mount jacks finally came in the mail yesterday, so I went right ahead and wired one up to my radio. I used the wire from a busted set of ear buds because it was handy, and the whole process went pretty smooth.

I tested the radio last night and luckily it still works just the same as before

I had to wait till today to test the jack since I couldn't find a cord to connect my iPod.
There are 2-3 issues to figure out:

-the radio does not cut out when the jack is plugged in
-the music only plays out the right speakers (front and rear)
-the mp3 is a bit quieter than the radio (this is because of the thin, long ear bud wire used)

I found it odd that there was only one source wire to the volume pot, yet a left and right source needed to come from the jack. I just soldered both to that pin, so that could possibly be my reason for only coming out the right side? No idea why it doesn't cut out the radio, I was under the impression that it was supposed to.

Aside from these things, I can turn the radio to a channel with no music or white noise and hear my iPod just fine with the volume turned up a little. This is far from ideal, but at least I'm part way there!

[Baskinator]

Here is the volume pot, I removed one of the connections from the jack. The orange wire with heat shrink over it goes to the empty tab originally.


Here is the underside, each colored X indicates the color of wire (coming from the pot) that is soldered to the corresponding space.


I cut the orange wire from the jack and the radio continued to play, so the orange wire is not the tuner source like I thought. Now I'm second guessing myself on what wire is for what. I have the ground connected to the purple wire, so that should at least be correct since it sort of worked. Can anyone tell me what each wire is for?

[Baskinator]

I got an excellent response from member gryzynx on the AMC Forum. My second attempt was not totally successful, but the third one's the charm. Here is what he sent me:

Hi Phil,

Well, I see a couple things in your post.

First of all, the potentiometer is set up slightly different than the older style in Nali's post. The orange wire you removed is part of the balance control circuit and the empty tab is not an input/output, but it is a somewhat unusual configuration in that it is a fixed tap for the circuit. I would suggest you reattach the wire.

The connections you need can be traced in the second photo. The connections you need are the two solder positions just above the white X on the printed circuit board. This is quite different than what you see in Nali's post where the wires go directly to the volume potentiometer rather than thru a printed circuit board like yours does.

Now for the good news. The connections you need are the green and brown wires you see just up and to the left of the brown plug with 4 wires in your first photo. There is some more good news here in that you are using a stereo radio. That means you have left and right channels unlike Nali's radio which was mono, (one channel only).

The modification described in Nali's post is essentially 1/2 of what you need to do with your radio. You also can do away with the resistors mentioned as your stereo radio has 2 channels and there is no need to mix your MP3 player output into one channel. If you add a second amplifier and switch to the drawing Nali provides in the last post, you'll get the idea. I would suggest using capacitors as discussed.

The jack you are adding will have 5 connections. One is a ground and should be connected to the same point as the shield wire as shown in your second photo. (grey cable containing red, white and shield wires. The green and brown wires are the left and right audio from your radio tuner to your amplifier input. The wires need to be removed from the printed circuit board and redirected to the normalling contacts of your jack. The tip/ring contacts need to be wired to the positions the green and brown wires were removed from thru capacitors as discussed in the post. I will disagree with the values Nali suggests. 0.05 microfarads will be adequate, somewhat bigger, say up to 1 microfarad will be OK. Keep in mind the normalling and signal contacts make 2 separate paths with your stereo radio. Do not tie them together like the original post suggests and make sure the paths from the green and brown wires, thru the jack and capacitors, back to the printed circuit board remain the same, i.e. do not mix them up.

Hope this helps,

Ray

I need to change the ground, as I didn't notice that he stated where it goes. Luckily again I didn't kill it, even the Eagle radio is a beast haha. I'll update soon with the hopefully finished product and photos.

[Baskinator]

Fixed! For anyone looking to do this, here's how. It would be better with capacitors like gryzynx said, but it works fine without them. Mine plays very similar to the radio quality, just without the usual static.

Remove the top and bottom case to your radio. You will need to find the brown and green wires at the top left of this photo, near the volume potentiometer. Ignore the rest of this photo, the wires on the pot don't have to be touched.


From underneath, use a small screwdriver to pull these wires out into the open. These are the left and right radio source wires.


Cut them in the center to give enough slack on each side and strip the ends off.


I used some info from this instructables, so when I talk about the jack pins, I'm referring to the picture given here: http://www.instructables.com/id/Adding-Auxiliary-Input-for-an-mp3-player-to-an-O/step2/Background-Information/

Before you do any of this, find where the wires will run out of the case and put your heat shrink on them.
Pins 3 and 4, the normalling contacts, need to be attached to each of the wires on the left coming from the radio source. Pins 2 and 5, the tip/ring contacts, need to be attached to each of the wires on the right going to the green board. Pins 2/3 and 4/5 must be on their respective color wires.

The ground wire from Pin 1, the sleeve contact, goes to the shield wire. This is the third wire next to the white and red ones underneath, as shown here.


Run the wires as you see fit. They can go out the back along with all the others. Put it all back together and you now have an aux input to play your mp3 player through!

Do this at your own risk. If you short something, you could screw up your radio. My connections weren't perfect and my radio only plays out one side now, but I don't care about the radio enough to go back and fix it. My iPod, however, plays great through all four speakers.

Edit:

I found the reason for the radio issue and will have to warn you to be VERY CAREFUL when soldering the pins on your jack. The plastic melts easily and will screw up the positioning of the contacts inside, ruining the normalling contacts for your radio and potentially rendering the jack useless. Mine is fixed now and everything functions perfectly.

A good idea for quality/safety is to run a capacitor on each of the source wires attached to pins 2 and 5. Use 0.05 - 1 microfarad, no more, no less, then  solder and seal them properly.


If you prefer to attach it to your dash, you will need to drill a hole where it's going and use something to grind the inside thin enough to fit the nut on the other side. I used a dremel.


Here is my finished product.

[captspillane]

Nice work Phil. That's really pretty slick.

[Baskinator]

Couldn't have done it without Ray's help, I never would have realized those wires were for the radio. If you want one in one (or more) of your Eagles, I have three spare jacks. They were so cheap I figured I'd rationalize the shipping cost with multiple jacks. Still, $7 and no dash mods beats shelling out for a new stereo.

[vangremlin]

Very cool!  Thanks for the excellent How To.

[Baskinator]

I found some really nice, thin speaker wire in my room that I totally forgot about and decided to redo everything to look and perform properly. After going to finally test it out again, I found that the jack I used was melted and ruined which caused the normalling contact for the left speakers to separate and the jack could no longer be inserted. Luckily I had more than one and soldered the wires onto another, proving more difficult than I'd initially thought.

The "How To" is updated with further information and the outcome of my creation.