Switching from Am Mono To Am/FM Mono
 

So My original set up was just a AM radio and stereo 8 track with proper harness.Converted to a AM/FM mono radio.In both set ups the rear speaker only plays with the Stereo 8 track.Both Radios only through front speaker ,even though there is a rear speaker spade on the 5 spade connector coming from the radio but not used by my harness set up.Can I just run a single wire from the rear speaker radio spade and tap into the rear purple speaker wire, and have the radio play through the rear speaker also.???Or just get a stereo harness thats meant for a red dot stereo radio?

Based on your user name, is this an F -body?

yes a 74 formula but I just realized something.Must be getting old,which I am.To get the Am/Fm radio to play in both speakers,you adjust the fader control in the 8 track.Been so long since I used one of these.LOL

I don’t think that should be the case actually. Each device has its own amplifier thus its own fader. Actually I don’t believe mono radios have a fader (or balance as I think it’s technically called).

Just so I’m clear too, do both speakers play when a tape is inserted? And your radio (AM or AM/FM) only plays from the front speaker?

After reviewing the service manual, I’m not positive what I said above is accurate since I’ve only had experience with a stereo radio and tape player, never a mono. I did find a service manual for the tape deck so I’m reviewing that to see if I can provide a better answer for you.

Thats ok,as it works as set up.The radio does have a fader control also but since there is no direct rear speaker connection to the radio,only connected to the 8 track,and since the power goes to the 8 track first then to the radio,that is proably why it operates this way for simplicity of wire harness assembly.The 8 track once a tape inserted automaticly cuts radio power and plays in both speakers since it is stereo.I am not sure but I suspect the red dot stereo radio has a modified harness so it has direct wire also to the rear speaker but?

With a stereo radio, both speaker outputs from the radio go to, and through, the tape player and to the respective speakers with no tape inserted then, as you said, when a tape is inserted, the player takes over those speaker outputs. What confuses me is, according to the manual, a mono radio appears to have only one output to the player. What I wanted to see is if the player then splits that signal to the two speakers. I wouldn’t think so as that would cut their output in half I’d think.

Either way, you have sound from both speakers during radio playback now?

No I think the signal stays mono from the radio and 8 track, even though it goes through the 8 track player which plays stereo.

As you indicated, the mono and stereo paths from the radio is dictated by the correct radio to tape player harness irrespective whether the radio is mono or stereo. I've attached some diagrams from a 1971 Delco Radio service Manual and some colored diagrams from a '67 T200 and mono radio to illustrate how a mono signal is switched through the harness to the fader L-pad within the tape player to drive the signal to front and back. When a tape is inserted, the mono path is severed and each stereo channel from the tape player is sent to a speaker.

Wow, great info. I learned something new. And your schematics are much clearer than the ones I found. Sorry for any confusion I may have caused.