Poor man's AUX port

[fosterb]

I've got a basic 94 automatic Camry. No thrills! The stereo has a separate tape deck--which I'm sure you guys are familiar with if only because you probably threw your's out. Replacing it would not be expensive, BUT I prefer free. (I had done the same thing for my ford explorer... which is currently pending the grim reaper's arrival.)

The connection between the stereo and the tape deck is not fully understood. It is a Fujitsu ten unit of some sort. The connection is a DIN with 13 pins. I've found the following resources:

http://www.geocities.com/lamberts.geo/aux.html
A simple adapter for a miata. A switch connects external source to the inputs, otherwise the inputs are gounded. On my camry, connecting an audio source does emit some weak audio, however the FM radio remains on and over powers the aux.

http://mazda-speed.com/faq/audio/#Round
A pinout of the connector. Some of the pins really do work. For example MUTE turns off the amp. I can't quite figure out what "System On/Amp Control" and "System Control (Play)" because they appear to be inoperative when connected to 12V or 0V. The signal "System Off" appears to cause some problems and should be grounded (radio may not turn on otherwise!). No idea what "TNS+" is.

http://www.itsayellow.com/girls/subaru.audio.html
Similar pinout. Signals are controlled by 12V inputs... "System On/Amp Control" is documented as "CD Play (or Remote Amp In) (send 12V to this to activate amp for remote device)". (I read this as, must be high to turn AMP on, but it appears to do nothing.)

http://www.sonic.net/~fosterm/miata/
Hooking a CD player up using the pin outs. Sadly doesn't entirely work!

Anyhow I can make output, but I can't seem to mute the FM radio. I've tried toggling pretty much every line. Only MUTE had muted the audio. Perhaps it is some other combination of signals. Any ideas?

Thanks!

P.S. what a pain in the butt... this forum keeps logging me out after a few minutes. So by the time I wrote this I nearly lost my post!

P.P.S. I think I've got a bad battery as well. In cold weather the starter does not start well--I suspect battery because the lights get dim, the dashboard flickers a bit, and then it goes dark for a bit. The radio, lights, etc works fine though. I measured the voltage on the accessories rail at 10.xx volts during my testing for this project. Seems low to me. The battery terminals definitely needs a clean too. I couldn't find a date on the battery. I sure hope it's only the battery...

[Zviator]

remember to check the "remember me" box next time u log in.

[sk8ersublime]

for the battery problem, clean your battery posts. I had a very similar problem a few weeks ago and even though they looked clean, my car wouldnt start until i cleaned them with steel wool.

[fosterb]

Update -- for all the cheap bastards out there I present my solution:

Pin6 - FM Off (active high, i.e. tie to 12V to enable radio)
Pin2 - Audio Left +
Pin1 - Audio Left - (likely -- I used pin5 signal ground instead)
Pin4 - Audio Right +
Pin3 - Audio Right - (likely)
Pin13 - Full System Mute (active low(??), i.e. short to ground to mute all audio)
(See http://mazda-speed.com/faq/audio/#Round for the order. The Sony CD mod which I reference next gives wire colours if gutting the tape deck which were accurate, but I would always double check first.)

No other pin (except power rails, as documented at other sources) has any effect. I believe the diagrams on other sites have the audio lines swapped. (Different car... I guess slightly different pinouts. How annoying.) (Although I did ground PIN11 too... but I'm not sure that has any effect!)

I removed the guts of the tape deck. I removed the Dolby button and added a switch ( Pin6 -> 1K Resistor -> 12V (acc)) on the original face plate PCB. (The switches on the tape deck PCB were not of the right type needed for this--I grabbed a random one from a parts bin.)

I then pulled an AUX cable through one of other holes left by the gutted tape deck and hooked it up to the audio signals. I would have also added a relay or a better switch so that the audio lines aren't floating when not enabled but since I probably won't use the radio it's not a problem. (See http://www.sonic.net/~fosterm/miata/ for example.)

A neat effect of this setup is if you attach a GPS and use the radio, the GPS instructions will be mixed in to the radio's audio stream (if Pin6 is low). Of course, the radio will need to be sufficiently low to hear to instructions!

Update2: Pin6 should be pulled high (I used 1K resistor). Oddly enough it worked fine when tied low too, but not when head lights were turned on. Flipping on the AUX switch now also turns on the radio if it was previously off.