Radio Problems

[sagnoff]

My '67 radio sounds so distorted that it's unuseable. According to County Corvette the radio and speaker have been rebuilt. I can tune in stations, but not clear enoght to hear. Assume the speakers the probem. I'm going to buy a new one from LI and see if it make a difference. I've heard about "antenna tuning". What's involved for a '67 and could this be my problem? Help!

 

[Mac]

Take it one step at a time. A radio system isn't complex so you should be able to troubleshoot the problem(s) yourself or with any car audio shop.

Since your radio & speaker were supposed to have been rebuilt, I'd look at the antenna first. "Antenna tuning" generally refers to getting the right length of antenna for your receiver for the waveband you're using. Since the AM/FM bands are well established, this shouldn't be an issue. That being said, if your antenna has failed (which happens) it could cause the problem you're describing as well. Get an antenna from the wrecker. It doesn't matter which make/model of car it's from- only that it has the right connector. Plug directly into the radio. If that improves your reception and output, you've found your problem! Get yourself the "proper" antenna. If you replace the antenna, replace the antenna lead at the same time. Common sense, right?

As a second step, look at your speaker. Before you buy new speaker, make sure your old one isn't working. A speaker can only output what it's being given by the radio. If the output from your radio isn't sufficient or clear, your speaker will sound like crap but it's not the speaker's fault. Unplug the speaker and use another audio source which you know is functioning properly (ie: you can bare the wires from a cheap set of earphones for a walkman) and test the speaker. If the audio comes out clear, your speaker is okay. That doesn't mean your radio is toast; check the speaker wires next.

If these steps don't find your problem, then you're going to be looking at the radio itself. Use a 12v test lamp to make sure there's sufficient power to run the radio. If the power isn't an issue, then your radio is the problem. Since these things aren't really user serviceable, I would send it back to the shop that rebuilt it.

Good luck!!

-Mac

 

[sagnoff]

Thanks for the comprehensive response. I don't think it's the antenna as I have tried what you suggessted. The speaker looks old, maybe the trasformer went? I like your idea of trying to drive it with another source. Will that work as the '67 speaker has it's own transformer?

 

[Mac]

Every speaker is a transformer of sorts- changing electrical signals into vibrations or sound waves. :L

Chances are a built-in transformer is there to protect the speaker from DC voltage or to act as an ignition noise suppressor. I haven't seen something like that before in car audio (I've never worked on a 67 Vette either!) but it's possible. That shouldn't interfere with an audio test.

In your first post, you said the speaker had been rebuilt. Normally, speakers aren't rebuilt; they're tossed because it costs more to rebuild them than they're worth. If someone was trying to preserve originality a "survivor" car, I could see them attempting a rebuild but I doubt speakers are judged (how would they do that??) so I would swap it.

If you are replacing the speaker, I would replace the speaker wires as well- for the same reason as I suggested changing the antenna lead.

-Mac

 

[1KULC7]

Mac is right. You don't rebuild speakers. Chances are you speaker is shot. Also, I read someplace on this Forum when you replace the speaker replace it with the stock type, as the newer speakers don't work quit as well. I forget exactly why, but I do remember people saying this...can somebody refresh my aging memory on this subjet....:confused

 

[JohnZ]

The midyear radios were designed to operate with 10-ohm speakers, which is why they had the matching transformer on the OEM speaker. Modern-day speakers are usually 4 ohms, and if you substitute one of those, it will eventually fry the (expensive) output transistors in the radio. Make sure any replacement speaker is at least 8 ohms, preferably 10 ohms.

Check to make sure your antenna is grounded to the frame - there's a solid copper ground strap from the metal ground-plane below the antenna body on the underside of the rear body panel to the frame, just forward of the #4 body mount on the driver's side; if that strap is missing, the antenna's ground plane (only required on fiberglass cars) won't be grounded, and reception will be weak.

 

[JJS]

Who needs a radio when you can just sit back and enjoy that engine growl?
I very rarely use my radio on while driving the Corvette.....it's weird, but I just love that sound!

 

[Ken Anderson]

My .02.
Antenna adjustment trimmer is for the AM band only. Your fixed mast antenna @31" is set for proper FM reception. Don't settle for anything less than a proper 10 ohm speaker, because your output TRANSFORMER will overheat and smoke if you use the wrong speaker setup. To test your antenna ground, grab hold of it with the radio playing (engine off) and if the radio gets louder, then you have a poor ground. Speakers can be rebuilt as good as new by professionals and a 35 year old speaker needs rebuilt or replaced. If your radio has been rebuilt, it would perform better than new, because a proper shop would replace all the paper capacitors and the original radio is then just as sharp and clear as a modern radio. Corvette 63 up radios can be restored to better than new operation for less than $250 & will work great and last a long time.

 

[Ron Miller]

My .02.
Antenna adjustment trimmer is for the AM band only. Your fixed mast antenna @31" is set for proper FM reception. Don't settle for anything less than a proper 10 ohm speaker, because your output TRANSFORMER will overheat and smoke if you use the wrong speaker setup. To test your antenna ground, grab hold of it with the radio playing (engine off) and if the radio gets louder, then you have a poor ground. Speakers can be rebuilt as good as new by professionals and a 35 year old speaker needs rebuilt or replaced. If your radio has been rebuilt, it would perform better than new, because a proper shop would replace all the paper capacitors and the original radio is then just as sharp and clear as a modern radio. Corvette 63 up radios can be restored to better than new operation for less than $250 & will work great and last a long time.

And I agree with the above. In addition, a faulty radio can also sound like a bad speaker. You should be able to hook both your radio and your speaker up to both a good radio and to a good speaker separately for a short period of time (read 15-20 seconds) to determine which one is at fault without having to remove either for the test. Mis-matched impedance between speaker and radio won't hurt either for the short period required to check them out. I'd give a quick test a try if it were mine.