adding Aux Input jack to auto radio

[ModRob]

Have been studying this for several days--found quite a few posts about it, but no clear answers, so I thought I'd turn to my favorite answer crowd for help...
I have a 2001 Honda Accord that I'd replaced the factory radio/cassette/cd player unit because it wouldn't play my home recorded CDs. I have since found the method of burning the CDs that allows them to play in the unit, so I'd like to install back into the car. Even though I HATE the aftermarket units (don't find them as user friendly to me anyway), most offer the addition of an input jack so I can plug my phone into.

I want to add this Aux Input jack to my factory unit. Yes, I know there are pre-made units out there that do the job, but more money than I can see spending on it until I exhaust this possibility.

From what I can tell, the unit is made by Alpine, and I believe uses an "M-bus" if my reasoning is correct. (of course I know nothing of that protocol either--why do I keep hearing Sgt. Schultz keep repeating "I know nothing!"?)
On the back of the unit, the left connector of two is the "CD Changer" connector from what I can tell, and contains
14 male pins. I have the label from the unit that lists each pin, plus when I had it apart (was trying to use the cassette head ribbon-to-board connections to input the signal but failed) I took note of labels on the backside of the pins as well.

From left, facing the pins, I have:
Audio Com.....R.......NC........BUS....ACC....ILM Shield....Illumi (top row)

Shield
..GND............L......BUS.......BUS....MAIN......+B...........Illum Control (bottom row)
..........................Shield......GND....GND

I found 12 volts on the BUS, ACC, and +B pins.

I can see that the input audio goes to the L and R pins, and their grounds to the AUDIO Com pin. But, with unit powered up on bench, the input does not come through on any selected input. Pushing the CD button twice does nothing either. So I'm reading that maybe I have to let the unit "know" there is something plugged in to be recognized to let the incoming audio through? Tried shorting other pins (not powered ones) together, or ground, but no change. I'm thinking that maybe a voltage needs to be seen at the BUS pin so the unit will then mute and allow the new audio input? (at least that's what I've found in reading but no one knows for sure, or how much voltage...I found an offhand comment somewhere about 5 volts)
I'm afraid to start using the 12 volt pins for fear that, 1. I don't have a clue on what I'm doing (usually never stopped me before..haha) and, 2. I fear burning something else out. (seems I've smoked a resistor or something on the cassette board--now a little black diagonal bar shows on the display screen, but otherwise, CD and radio work fine, and display is ok other than the little black bar)

Of all the adapters I've seen for sale, they have a little box that I'm sure does something to make it all work together. But, I can't help but think that maybe many are overblown presentations of a simple process. Could it be as simple as the stock unit seeing some kind of signal voltage to a pin to trigger an override for the new audio input?

Thanks again for any guidance.

[Externet]

To add an external source input jack to a modern car radio, you will probably need the schematic of the unit, not only the connector pinouts.

I did it to my complex OEM Alpine car stereo by using the cassette audio path, which I will never use.

Somewhere on the board there should be among many, an integrated circuit that handles switching of L,R audio sources as AM, FM, VHF, cassette, disc... depending on selected mode. Get its data sheet to find out what pins are useable. Example: If you do not want cassette, probe which pins get the cassette head preamp output, lift those pins from the board traces and connect them to the added auxiliar jacks in the chassis back.
Then, when selecting cassette mode, the external auxiliar jacks will pass audio.
You may need to trick a 'cassette present' microswitch in there, and you will need very good fine skills for the surgery.
The AM radio source path is another option.

If the volume control is not digital, adding a switch may enable the extra inputs and disable the internals.
If the volume control is digital, better get the data sheet for that IC to find how to trick it.

Also: ----> http://www.electro-tech-online.com/thre ... ack.42692/

Miguel

[dacflyer]

long shot here..if your radio has a manual volume control, and you really know what your doing,
you could take a DPDT switch disconnect the wires going to the amp section of the radio, connect it to the center pins of the DPDT switch, connect your AUX jack to one set of the outer pins of the DPDT switch. then reconnect you other leads from the volume control to the DPDT switch..

then you flip the switch from radio to AUX, then the AUX will feed thru to the amp..

if it is all electronic volume control, then you have a whole lot of other work to do.. you will really need a schematic..

[ModRob]

Hey thanks again guys...

I've searched high and low, and can't seem to find a schematic on the unit. I've also looked at many other posts that found certain "areas" or "points" that new signals could be input, but on my unit, I can't find anything similar to their posts--in other words, my pcboards appear to be "newer", or that they are so streamlined there is just no available room to solder in the finest of wires. I did find the contacts where the ribbon from from the cassette head terminated into the cassette board--there were three on one side, and two on the other. However, they are so fine I had trouble trying to keep wires soldered to them, even to make a test. And again, that was a guessing game trying to figure which were which, but I felt I had a decent chance of getting a part of it right.

And for the "microswitch", I did find that little bogger--an actual manual switch that when the cassette was slid in, the top linkage pushed in a plunger on this tiny switch, so I assume that would be what tells the unit a cassette is loaded and to switch to that input. That part I figured I could work out manually, IF I could just get the audio to input.

I'll keep trying to find a schematic. Agreed, that would probably be a BIG headstart.

Thanks again.

[Externet]

Hey Rob...
You will need an oscilloscope to first probe the audio from a playing cassette into the pins of a surface mount ~32+ pins IC that handles the audio switching.
It MAY be a TEA6320 ---> Check pins 11,13,15,16,17,18,20,22 for which are L,R audio from tape.

---->http://www.nxp.com/documents/data_sheet/TEA6320.pdf

There should be another 8 pin IC for audio muting, like a 3703. Ignore it.

If you do not have an oscilloscope, try a junky audio amplifier fed with a sewing needle as probe, and a capacitor in series to its input as the audio may ride on +4VDC.
Look (hear !) the audio at ICs pins as above listed until get audio from a playing cassette. (No CD in, no antenna)
The tape pre-amp IC may be a TA7705F. Check pins 2,16 for audio.

Whenever you find the L,R pins for cassette audio in, mark them; lift them desoldering from the pads. Those are your external aux inputs but with a 1uF in series.
Miguel

[ModRob]

Hey thanks so much again for some valuable teaching...
No I don't have a scope, but I have toyed with the idea of trying to find one off CraigsList locally, but usually too expensive for my tastes, but I will keep looking--I don't think I'll ever tire of trying to hack things, so I might as well get one haha....

Uh...can't use the cassette function now--I took out the head and the attached ribbon cable...

I believe I finally found a Service Manual for a similar radio. Luckily, another poster like myself out of many happened upon it and linked it. I found it early this morning and was trying to glance over it before I fell asleep...
I'm getting ready to bring it up on my desktop so I can print some of it bigger (the 7inch tablet is horrible for that) and maybe get a better understanding of it...

I will dig into the link you sent as well here shortly, as well as your directions.

Oh yes, one more thing...I do have a little Radio Shack amplifier (small with a little speaker in it) that I usually use for testing...I have wired up needle probes from an old meter to the input jack of it. Is this what you mean? And just any kind or size of cap inline of the positive probe?

Again, thanks very much!

[ModRob]

Here is the ribbon that came off the head, terminating into a board attached to the Cassette mechanism. It is folded, sticks through the pcboard, where three points contact one side, and two contact the other side...
When I get deck apart again, I'll take a pic of that entry point...

[ModRob]

One more view of it...you can barely make out the fold in it..

[ModRob]

This is the point (where the ribbon soldered to the board) where I was trying to bring in the outside audio...

[ModRob]

codedradio.info/manuals/panasonic/cq-jh8061_62z.pdf

Here is the docs that I believe more closely resemble what I have, but other sources indicate the radio is Alpine unit. Some say Panasonic...no other descriptions on the unit itself...
But this schematic does show the 14 pin CD changer connector on the back of the unit, and the 20 pin connector is correct as well...

[ModRob]

Well drats! After taking unit apart again, I find no ICs or anything that has numbers that correspond with the Service manual I posted a link to...
So, I'll continue on with my search for a more exact item...

[Externet]

Those service manuals are usually unobtanium. Better get data sheets for the relevant ICs you see in there; will tell you what is going on and what they do on what pins.

Uh...can't use the cassette function now--I took out the head and the attached ribbon cable...

Well, did not need to take out anything. Just follow audio path when cassette plays as told before.

This is the point (where the ribbon soldered to the board) where I was trying to bring in the outside audio...

Wrong place to feed external audio, wrong level, wrong equalization, wrong impedance.

Oh yes, one more thing...I do have a little Radio Shack amplifier (small with a little speaker in it) that I usually use for testing...I have wired up needle probes from an old meter to the input jack of it. Is this what you mean? And just any kind or size of cap inline of the positive probe?

Yes, that is what I mean; that amplifier is perfect. Will tell where is the audio routed. Capacitor can be a 0.1 ~ 1uF in series with the probe.

The pictures of the flex cable are irrelevant. Put it back to were belongs or you will have no audio to trace. Just probe its traces on the connector it fits, not on the flex cable, 5 conductor = 1 common+4 heads; for 4 heads L,R forward and reverse directions selected by a switch somewhere in the mechanism, sent to its cassette unit on-board? preamp and then to the audio management chip on the main board.

4heads---->direction switch---->2 heads preamplifier---->mainboard---->muting chip---HERE->audio chip---->audio power amplifier---->speakers
HERE is where external audio should enter.
Miguel

[ModRob]

Ah....I'm beginning to see more and more now...

Yes, I have been doing as you suggested and looking up the chips, smds, and such. Interesting, but so many terms on them I don't have a clue about, but the more I keep digging in, it slowly starts to make just a tad bit more sense. I remember reading (seeing) mute chips in a couple of related Service Manuals, so I'm thinking if I can identify the right chip, then I might be able to find that audio in point you showed me.

I'm not very sure i can reattach the head, ribbon cable. Especially back onto the main board of the cassette mechanism. But I can try. If I'm reading you correctly, it would be best if I could have a cassette play so that then I could trace the audio with our little amplifer/probe rig?

Again, many thanks. Hope to get back on it within a day or so..

[Lenp]

After all this frustration and lost time maybe it's time to consider something simple. There are FM RF modulators online for under $20. If the cassette audio still works there are dummy cassettes with a tape head that induces the audio into the player's head for even less money.
But, If it's a man vs machine issue, then press on!

[Externet]

Rob :
If unable to reattach the head and circuitry and put the tape back into operation, there is still some hope. But you still need to identify the audio management chip.
Another way will be to plug an antenna, turn on the FM and look for corresponding audio pins on the audio management chip.
Mark which pins show L,R. Next, AM and identify which pins show corresponding AM audio. At zero volume !

----> Tell us the chip numbers you see on the main board, the ones having around ~32 pins !!
A good picture of the main board would help.

Miguel