Vintage car audio wiring diagram wanted.

[Kruse]

Wondering if anybody could help here. My brother has an older Realistic car stereo that he needs help with the wiring. It's in a grain truck built in the 70s, so obviously it's ancient. This system has a white plug with six wires and I was wondering if anybody could help me out with the wiring assignments. RS wants $22 for the complete manual and the radio itself isn't worth that.
Okay, the red wire is obviously the power wire because it has an inline fuse and inductor. I will assume black is the ground, correct?. Can anybody help with the speaker assignments? I'm hoping this is a standardized jack and somebody will know this from memory. TIA.

 

[eljefino]

Got a picture?

Typically one wire is speaker ground (for all of them) and the rest are "speaker positive".

If it has just balance you've got a stereo, stereo. I bet just two.

If you have a fader knob there'll be four speaker outs.

There's no harm in taking a cheap speaker and testing random two wires with it, the speaker has impedance and won't short anything out. You got the power situation figured out, get it to light up before you add any more.

You'll likely find the speaker ground pretty easy, it will be common among the outs. Your speakers will be marked with polarity (even if it's just a red paint dot), get them right or you'll be out of phase.

Play with the balance knob to figure left from right.

 

[Jimmy9190]

Red is power
Black is ground
It should have 4 other wires:

Green is left speaker +
White is left speaker -
Brown is right speaker +
Gray is right speaker -

I did find a list of Radio Shack car audio info here:

http://support.radioshack.com/support_auto/8737.htm

The model/catalog numbers are listed on the right side of the page. If yours is listed, click it and then click the link for "connections" and it gives the wiring info. The "operation" link gives the user info from the owner's manual. All info I found on that site was free. Radio Shack color codes were all the same for most models, so if you do not have the model number, chances are the info from one of the other units will still match the unit you have.

 

[Kruse]

Jimmy and eljefino, thanks for your help. I don't believe the model is listed, but with your posts, I believe I have enough info to get it to work.