3.5mm aux input for Delco Stereo

mickstan_vr · 11-15-2006, 10:27 PM

Help! I'm trying to get an aux 3.5mm input into my older delco stereo. A guy on E-bay has successfully done this. Here is the link: http://search.ebay.com/160050818626 . I'm assuming he's cutting the feed from the radio and replacing it with the feed from the 3.5mm plug at the cassette deck. Thereby fooling the amp into thinking its being fed by the cassette signal. I figured out how to cut the radio signal, but can't get a signal from the mp3 player. There are 5 wires connecting the tape deck to the rest of the stereo. I put a switch in the red wire. That cuts the signal going back to the amp in the red/white wire. I spliced into the other 3 wires with a 3.5 stereo receptecle. When the switch is thrown, it cuts the radio signal, and should allow the mp3 signal to pass to the amp. Should being the key word.
I have 2 of these radios taken apart on my workbench. I can post some pictures if that will help.
I can't figure out how this guy pulled this off.
Heres a link to another guy that was on the right track: http://www.filbar.org/weblog/integra...ory_delco_deck

Thanks in advance!

mickstan_vr · 11-16-2006, 08:12 PM

Man.....This is drivin' me nuts! I've got 2 of these stereos on my workbench that I've been tinkering with. Thier guts are hangin'out all over the place. And I cant get it to work! I figured out(I think) how he cuts the radio signal. There are 5 wires going to the cassette deck. RD,RD/WHT,ORG,WHT, and BRN. The RD and RD/WHT go to a micro switch that is Normaly Closed. They go nowhere else. The micro switch is tripped and opens up when a cassette is inserted, breaking the circuit. This disables the radio signal, closes the other half of the micro switch, and sends power to the cassette deck. Then the cassette signal travels down the 3 remaining wires to the amp.
So I added a switch to the RD wire. When thats tripped, it cuts the radio. The display on the front changes from a radio station to the clock. Just as it should when a tape is inserted.
I then spliced a 3.5mm stereo receptacle into the 3 other wires. And plugged in a portable CD player. Nothing. I hit the switch, the radio cuts out, the display changes, but no sound from the CD player. WTF? There are ONLY 5 wires from the cassette deck to the rest of the radio. I have tried those 3 wires in every combination on the plug.
This guy is doing something simple to make this work. Hes modding too many different radios for it to be too complicated. But they're all GM Delco radios. So there must be something simple and something similar in all of them.
I've got 1 radio from the '87 celebrity, and another from a '89 buick century. They look the same on the outside, but the cassette decks are built different. They are wired the same, and look similar, but use some different components. Whats crazy is the '87 looks more high tech than the '89!
I found a 3.5mm plug that has the SP/DT switch built into it. That way when the plug is inserted, it throws the switch at the same time. But I'm not getting one of those until I can get the prototype to work first.

davesaudio2 · 11-17-2006, 12:08 AM

He explains it fairly well, follow the wires back from the tape head.

in a 70s radio you could always input signal on the volume
control leads which were a traditional pot.

suggest you put a cap (~1-100uf) in series with whatever input signal you are driving it with.

mickstan_vr · 11-17-2006, 05:38 PM

You follow the wires back on the tape head and the go straight to the circuit board on the cassette deck. From there they split up and go everywhere on the board. Then they end up in the 5 wire harness and plug going to the rest of the stereo.
You'll have to bear with me on this. I have no experience messing with the insides of a stereo. I can put together a hotrod PC or wire a house, but I'm unfamilier with this stuff. Right now I'm just taking educated stabs at the problem.
I'll try to post some pictures to help explain.

mickstan_vr · 11-17-2006, 11:56 PM

OK...Heres some pics...

mickstan_vr · 11-17-2006, 11:57 PM

Heres the rest...

davesaudio2 · 11-19-2006, 12:33 AM

if I had no real test equipment
I'd put a small cap in series with "hot" lead of a line level input on a ghetto blaster/old stereo.
loosely assemble the thing, stick in a tape and
probe for the signal(music) path
should be present on that 5wire connector

but I'm not recommending anything (disclaimer)

mickstan_vr · 11-19-2006, 11:14 AM

Feel free to recommend away. I have no "real" test equipment and the 2 stereos that are torn apart are just for experimenting. If I screw one of them up' I'll go get another from the junkyard. My "good" stereo is still in the car. I know my set-up looks pretty primitive, but its all I've got to work with.
What will a capacitor do? Do I need to put just one in? The way I see it, I've got 3 wires on that plug to work with. One is a common ground, and the other 2 carry the signal from each channel of the tape. Would that be correct?

mickstan_vr · 11-20-2006, 10:25 PM

OK, so I played with this some more today. I took the switch out that I put in the red wire and put the wires back together. I then manually put the microswitch in the NO position(closing it). Turned it all on and got some signal from the line out on the cd player, but not from the headphone jack. The sound was not clear and the balance was screwey. One side had more signal than the other. Maybe I'm barking up the wrong tree here.
Davesaudio, could you be a bit more specific on where and how I should go with the connection at the volume pots?
Thanks

mickstan_vr · 11-23-2006, 05:23 PM

Alright..I got 2 100uF caps at radioshack and put them inline with the 2 channels from the aux input plug. I can now hear sound from the headphone side of the cd player. But its weak. I guess I need some smaller caps?

davesaudio2 · 11-23-2006, 11:54 PM

The point of the caps in series with your "hot " line level is to block any DC coming from your line level sound source.
keeps DC voltages on their own side if you like but passes AC (audio) signals. size should be ok for these experiments, suppose smaller and non polar would be safer, you do know electrolytics blow up if you reverse bias them?
not following when you say headphone jack- what/where is that ?

mickstan_vr · 11-24-2006, 12:54 PM

headphone jack: see picture DSC00090.jpg post #6.
Its plugged into the "headphone out" of the CD player.
I was getting sound from the "line out" of the CD player before adding the capacitors. No sound now, but I am getting sound out of the "headphone out" plug. Its not very loud, but its there. Even at max volume on the CD player, the sound is too low. This is how the iPod will work, with the sound coming from the headphone plug. I would prefer to get the signal from the iPod from its own "line out" but thats different mission.
I kind of figured that the caps only went one direction. I hope I got it right! They have an arrow shape on them. I have them so they point away from the CD player and toward the cassette deck.
Apparently, I might not even need a switch. It seems that if the signal from the CD is strong enough, it will overpower the radio signal.

mickstan_vr · 11-29-2006, 10:35 PM

I'm on the right track and still working on this!!!...............

Shadowfangs · 12-10-2006, 12:35 PM

Keep up the good work, Maybe when you figure it out you can write up a How-To or something.

accrdwgnguy · 04-10-2007, 10:31 PM

How did you make out on this adapter? I got a Delco stereo from a 93 Ciera in my 83 malibu wagon, and I'd like to do this to it. If you could sticy a walktrou or something, that would be sweet. later