924Board.org

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Ok, so I'm replacing an old radio in my RV, this thing is so old is has knobs and the radio is tuned by sliding the little tuner like a slide rule (if you have to ask...).

I pull the headunit out, if you can call it a headunit and I find that while there is a unique (+) for each speaker, there's a *common* (-) lead shared by all 4 speakers, rather than a (-) for each one.

So, I wire up the new unit with the (-) shared, and no mas, nothing out of the speakers. I bench tested the new unit with the (+) and (-) wired as they should and it makes beautiful music.

Anyone heard of this common, shared (-) setup before? I'd like to use the existing wiring and rather not have to run new wires all over the coach if I can help it but I don't think the new headunit will work with the shared (-) wires...

Thoughts? Advice?

932kiwi · Joined: 06 Dec 2009 Posts: 44 Location: Wellington N.Z

So thats how you spell cocamamie. thanks

!tom · Posted: Sun May 16, 2010 3:55 pm Post subject:

Yep, I've seen car stereos like that too. A brand spanking new one that I helped install in the '90's had the wiring just like that -- a common wire to all speakers, and a signal for each speaker.

I'd expect you'd find that exact same arrangement in most head units, although the connection might be internal to the box.
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78 924 NA
5-lug

9XX Girl! · Posted: Sun May 16, 2010 7:27 pm Post subject:

hmmm... that is abit of a thing of the past., Modern equipment shares nothing, in order to improve stereo interchannel rejection.

I remember car radios only having 3 wires coming out the back:

1) 12v supply
2) Ground
3) Speaker

You ran one wire to a mono speaker and then grounded the other side of the speaker.

They also had a polarity switch on them in order to determine the polarity of the radio's ground. this was so they could be fitted to positive earth vehicles. (yep, i have owned a positive earth vehicle)

Back then you only had one speaker, unlike now

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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

9XX Girl! · Posted: Sun May 16, 2010 9:29 pm Post subject:

_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Heh heh.

I rewired it.

Nobbi · Joined: 24 Aug 2006 Posts: 1398 Location: Germany

Ahem, speaking about stereos. I connected a "test-lamp" to the ignition switch and put the tip from the lamp on the chassis of my radio and the lamp shined bright......is that normal?

And yes, my friends are not electric...

Nobbi

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NA 924 - april/1977- 4-speed-audi gearbox.
500.000 km with fun.....and new toy:Porsche 944 S2 Cabriolet.Other car Daimler c-class cabby,brandnew..Plus : DEUTZ 4005 tractor Built 1967

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Naw, its a crapo headunit but hey, it works. Better than the one with the buttons.

The RV has a really cool chrome wheels, an awesome stereo (now) and a big wing on the back (really). I guess you could say it is kind of like a giant tuner RV, but from 1984. Quite the sight. Kind of a blend of the Space Shuttle and Fast and the Furious.