My original stereo radio lights up the "yellow stereo light" as it passes over local stations. There is no music, voice or even static to the speakers. Totally silent.

Any suggestions on where to start.....I am thinking the radio is OK but the "amp" behind the passenger dash side might be the problem. I am pretty good with mechanics but pretty weak with electricals! I can barely use a multi-tester.

Help ... Thanks ...

 

The 'convector' under the passenger dash pad is merely the final stage of amplification for the radio. An AM/FM Stereo radio will have two transistors (one for each channel). The only components on the convector are the transistors and some wafer capacitors. The convector should be very easy to test using an ohmmeter. Use Google to find procedure for checking transistors and capacitors. You will likely have to break some connections to get that job done. An alternative would be to swap out your convector with another one to see if that changes anything [or not]. Other than those options, you will need an oscilloscope to dig any further.

Don't forget that the speakers could be defective and/or the wiring could be cut or disconnected. From your description, the radio head is receiving the stereo signal, but that doesn't mean that the audio signal is being processed correctly in the head unit.

 

 

Charley steered you right!

A tip; start with the speakers. 99% probability they have open connections going to the voice coil. The 70-76 4X6's are failing like popcorn due to deteriorating materials - especially under the black (now brittle) liquid tape type protection that you will see on the front of the paper cone. The thin wire fractures.

Gain access to the speakers, disconnect the cables from the radio to each speaker and put your continuity tester across the green & black leads. If you read an open circuit, call Greg at 877-780-2681 and ask about the vette speakers he just had reproduced. They are excellent and not even on his web page yet - www.turnswitch.com/speakers.htm.

It's very, very rare to find that the transistors on the convectors (any year DS-501) have failed. They degrade, mainly because guys put speakers with no loading coils in place of the originals on the 58-67's way back when. But they are very rugged devices.

Nutsy just went through the same situation - http://forums.corvetteforum.com/c3-g...-speakers.html.

Good luck with the troubleshooting!

Jerry

 

Thanks everyone....I will start at the speakers and be in touch!

Fred

 

hi JERRY and FRED. yes, FRED, JERRY helped me greatly and found my speakers were the problem. as he said the material on the speakers was brittle like an old peice of paper and the wires became unattached to them. i also got the speakers from GREG that he recommended. they wont blow your ears out but there better than what i had before. they also come with very good instructions and spacers to install them. good luck.

 

Hi Brian!

Fred's 74 radio may be much louder than your 72 if he has the stereo version. In that case he would have a separate amplifier for each speaker - double the power available to drive each speaker. The 68-72 stereo models are the same way and are one of my favorite models for power and clean sound among the 58-76's. Plus, with an auxiliary input jack (IPod type), it's a real performer in full IPod/XM (etc.) stereo.

Your radio should be pretty loud Brian... most all of these monaural radios suffer from the proverbial "aged" electrolytic capacitor syndrome. Once those are swapped out, the radio comes to life in a very noticeable way again. Something like swapping 50 year old spark plugs... If you know a Ham radio operator, have access to a RadioShack and get a six pack (which the Ham can't touch until the job is done), the parts can be swapped out in one evening.

Fred, Greg reminded me that the 4X6's ARE on his web page but are shown without the cork gasket and fabric dust screen. I use them as a standard here on the service bench. The extended "throw" of the speaker cone allows for improved bass response. Mine came with the correct harness attached although the site doesn't show them. And for those of us from the old days that thought big speaker magnets were always better - those little neodymium jobs are incredible. Use them on your refrigerator and the kids will never get their pictures back off.

One last thing; the big transistors on the heatsinks (convectors) each have a fusible resistor in series with them (inside the radio) for protection. Those almost always burn out long before the transistors go. None of this should be a big enough deal to need a new radio.

Anyway, cheers to all, thanks to Nutsy and good luck with it Fred.