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Discussion Starter · #1 ·
I have a 66 AM radio and I have 3 tabs Pwr, spk, gnd. If I apply 12v+ to Pwr and 12v- to grnd there is 12v to the light.

I don't have an ant or 1 wire speaker.

I'm guessing that the 1 wire speaker uses ground as neg just like the light does.

Q. do I run the 1 wire to the + on a speaker and ground the - from the speaker to the radio?

Q. can I get sound without an ant and if no, can I toss an ant into the glove box or somewhere just to prove the radio works? I'd then let the next owner figure out what to do past that. (There's no at hole on the car).
 

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I have a 66 AM radio and I have 3 tabs Pwr, spk, gnd. If I apply 12v+ to Pwr and 12v- to grnd there is 12v to the light.

I don't have an ant or 1 wire speaker.

I'm guessing that the 1 wire speaker uses ground as neg just like the light does.

Connect the negative speaker wire to chassis ground.

Q. do I run the 1 wire to the + on a speaker and ground the - from the speaker to the radio?

Yes and answered above.

Q. can I get sound without an ant and if no, can I toss an ant into the glove box or somewhere just to prove the radio works? I'd then let the next owner figure out what to do past that. (There's no at hole on the car).

You will not get any reception without an antenna. Antennas have to be a specific length to work properly and work best outside the car. You can use a Greenlee hole punch to make a clean hole in the body and feed the cable to the radio.
Note these radios used a 10 ohm speaker and an 8 ohm at hi volume will damage the amplifier in the radio.
 

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Discussion Starter · #3 ·
Note these radios used a 10 ohm speaker and an 8 ohm at hi volume will damage the amplifier in the radio.
Ok, I remember hearing something about that years ago. I'm pretty sure I don't have a 10 ohm speaker, so I should be able to see if there is any voltage coming out of the spk wire right?

In other words, if I hook up a volt meter to the spk, I should get a reading that would indicate that it works, right?

The other question is where do you get a 10 ohm speaker and can you convert a modern one to 10 ohm?

According to this:
4 Ohm vs. 10 Ohm Speakers - Team Camaro Tech

I can run more than one speaker to get close to the 10. Seems like there's an on going problem getting 10 ohm speakers. I'm no expert, but shouldn't a resistor or other thing convert this?
 

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There are places that specialize in old car speakers and there are a bunch on ebay. There is limited output with the old radios and they will not power a bunch of speakers.
DELCO 4 X 10 10 OHM SPEAKERS | eBay
 

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Discussion Starter · #5 ·
This is a bit odd, I just went out and looked at the dash. There's no windshield so I looked down at where I would expect the speaker to be and I see no speaker.

I say odd because why would anyone remove the original speaker?

Anyways, from that link above, it looks like a simple resistor will do the trick. I don't need to invest in a speaker that will probably never be used, I just wanted the radio light and some kind of sound to come out. It'll probably be replaced with an iPod and an amp, that's what I do in my other cars.
 

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Because your increasing the current draw by 20%. I've seen it happen on these old radios, the power transistors are not that strong. If it weren't an issue they would not be using 10 ohm speakers from the factory when 8 ohms were pretty prevalent in the aftermarket.
 
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Because your increasing the current draw by 20%. I've seen it happen on these old radios, the power transistors are not that strong. If it weren't an issue they would not be using 10 ohm speakers from the factory when 8 ohms were pretty prevalent in the aftermarket.
Best run an amp.. Run the speaker lead into both hi side jacks. That way you can run 4 ohm speakers you want and take the work off the radio..
 

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Years ago I always thought that when they called out something such as an 8 ohm speaker, a 10 ohm speaker, or whatever that this was a constant load to an amplifier's output but it is not. The impedance changes with frequencies.
I bought a Rockford Fosgate Impedance meter years ago and I could hook it up to let's say a 4 ohm speaker and at one frequency the impedance was 4 ohms but then at another frequency it might lower to 3 ohms and then yet at another frequency the impedance might rise to 20 ohms. It was interesting seeing how the same speaker would have different impedance curves depending on the enclosure it was in. Using the meter came in handy years ago when amplifiers could not handle a lower impedance than they were designed for as some amplifiers back in the day if the impedance dipped too low, the protection circuits kicked in.
If you measure the DC resistance of a 4 ohm speaker, the resistance might be 3.2 ohms or so but then put music through the same speaker and now it's impedance varies.



Getting back to the original poster's question, here is what I found as being a 1966 Chevelle AM radio and it has the illumination light socket on the topside with a wire off of it that goes into the interior of the radio's steel chassis.



If yours is like this, and you just would like to have it light up and not have any speakers hooked up nor an antenna, maybe think about taking the radio apart and unsoldering the power wire where it is attached inside the radio and then do the same to the wire off of the top lid that illuminates the radio display. You could then connect both of these wires together using some heat shrink tubing over the connection once they are soldered together and then once reassembled, the radio itself will not get power but the accessory 12V off of the plug is sent directly to the illumination bulb. Granted it would be lit up when the ignition is on and not work off of the dash dimmer circuit but with enough thought, you could redo the light socket on top and run a dedicated wire to the fuse block for a dimmable 12V.

Jim
 

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Because your increasing the current draw by 20%. I've seen it happen on these old radios, the power transistors are not that strong. If it weren't an issue they would not be using 10 ohm speakers from the factory when 8 ohms were pretty prevalent in the aftermarket.
I think you need to look at the top of an original Delco radio sometime and read what it says imprinted into the sheet metal.

I think you also need to think about factory fader equipped radios.

BTW, I've worked on many vintage Delcos.
 

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Best run an amp.. Run the speaker lead into both hi side jacks. That way you can run 4 ohm speakers you want and take the work off the radio..
I hope the amp provides the proper impedance. If it's too high of impedance, that can damage the radio just as quickly as too low of impedance--i.e. like someone running 4 ohm speakers on an original radio. It would depend on what the "high" input of the particular amp represents impedance-wise.
 

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Discussion Starter · #12 ·
That pic is what I have. I ran the numbers and it is a 66 chevelle AM radio.

The car doesn't have an antenna and I don't intend on putting one on the body of the car as that hole welded shut.

What I want to do is figure out if this radio works.

When I apply power, the on/off operates the light on the top.

The tuner moves, the next question is does any sound actually come out.

I have speakers so I should be able to run a test. I can also see if any voltage comes out.

Q. Will an AM radio product sound without the antenna?

Q. I have an Inf Ref 6X9 2ohm -- will a 10 sec test blow up the radio? Should I just check for voltage output at the spk lead?

I don't want to install a broken radio.

As far as the iPod, I just run it as a separate system. Amp, speakers, wire to iPod that sits on the center console. Remove or hide iPod when you leave. Pretty simple, no need for any head unit.
 

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That pic is what I have. I ran the numbers and it is a 66 chevelle AM radio.

The car doesn't have an antenna and I don't intend on putting one on the body of the car as that hole welded shut.

What I want to do is figure out if this radio works.

When I apply power, the on/off operates the light on the top.

The tuner moves, the next question is does any sound actually come out.

I have speakers so I should be able to run a test. I can also see if any voltage comes out.

Q. Will an AM radio product sound without the antenna?

Q. I have an Inf Ref 6X9 2ohm -- will a 10 sec test blow up the radio? Should I just check for voltage output at the spk lead?

I don't want to install a broken radio.

As far as the iPod, I just run it as a separate system. Amp, speakers, wire to iPod that sits on the center console. Remove or hide iPod when you leave. Pretty simple, no need for any head unit.
2 ohm impedance speaker on an over half century old as-is radio? Only if you feel like tempting fate...

If you have already powered it up, with no speaker connected, you can damage the audio output circuitry as well...

Don't you have an old stereo /bookshelf speakers laying around to test the unit with at least 8 ohms of impedance?

Even With no antenna, you will still hear a "thump" from the speaker at turn on if the audio output circuitry is still functioning from the speaker cone moving away from center with the DC bias voltage on the voice coil. You may or may not hear a hiss depending on the condition of the electrolytic capacitors which are all questionable at this age.
 

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I do remember how I smoked a Chevy radio years ago, ( 1966 or 1967) If I remember it was a - DS-108 ???. How did I do this?????? I just turned the radio on with-OUT a speaker attached, or NO LOAD. ( the gain was up )
Since 1962 I have been playing bass in a band, I always used 2-JBL-D-140s @ 16 0. Wired to see 8 Ohms. WHY? If your power amp. output is lower than the speaker load it will work. If the speaker load is lower than the Amp. output.
You will have a chance to stop and smell the smoke !
My Gallen Kruger ( solid State) is 4 O. So I use a 4 O. NEO. 15" speaker. My 1970 Music Man HD-130 ( Tube Amp) Has toggle switch on the back for 4 or 8 Ohm.
When I use a SINGLE 16 O. Speaker I switch it to 8 O. and it works fine. I do know a tube amp is WAY MORE forgiving than " ANY " solid state amp.
I have learned in my 76 years on the planet, DONT screw with a mis matched ohm load on a solid state amp.
Also ,,, Depending how the speakers are wired, ( Series-Parallel ) is a MAJOR FACTOR. :nerd:
Bob
 
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