My '71 is one of the 600 or so (I believe) '71's for which the original owner did not select any of the radio options. That means it came with a block off plate. According to the original owner, a year or two later he went back to the dealer and had the AM/FM (non-stereo) unit installed. When I purchased the car a year or so ago, he told me the radio worked for 42 or 43 years, but stopped working recently.
Sitting in a quiet garage with the engine off but the key in the accessory position, I recently discovered that (1) the radio face still illuminates when powered, and (2) an extremely dim amount of noise emits from the radio. I may be crazy, but it sounds more like it comes from the head unit than from any speaker. I can even tune the radio to different FM stations, but it is very, very quiet.
I am not an electronics guy. Any idea what the problem might be? Any easy fixes? Here is a pic of the side of the radio with the access panel portion of the lower dash removed.

 

Hi 71,
The radios can be repaired …. often at a reasonable cost.
I suggest you contact Jerry Rudbeck at ElectroDesign.
I'm not sure if he's still doing repairs but he's where I would start.
Good Luck!
Regards,
Alan

Very interested in the rear deck of your no radio car.
Was the hole for the antenna not drilled or was it drilled and patched?
Thanks!

 

Alan -- Someday you will need to come out to Delmarva and take a look. The dealer installed an antenna when they installed the radio, presumably in '72. From underneath the car, I can see a sticker with a part number next to the antenna, the light isn't good enough to tell whether any evidence remains to determine if they patched a hole in St Louis, or if they simply didn't drill antenna holes on my car and its 600 brothers. I've also wondered if my car left St. Louis with any speakers.

 

It may be a bad "convector"-GM's name for the external amplifier. It is mounted to the metal frame behind the passenger side lower dash. It's a simple device, consisting of only one power transistor mounted to a finned heat sink. If there are any "old fashioned" TV or radio repair shops in your area, they can easily test the transistor and replace it if needed.

 

Hi 71,
Thanks for the info.
I'm really not sure when it was determined that a deck panel was headed for a radio or no radio car so I'm not sure how the hole was handled.
I'm led to believe that all decks got the hole and it was patched on those not getting a radio.
Here's a picture of the decks ready for shipment…. no holes at least at this point.
Regards,
Alan

 

The existence of a patch on my car would have given the dealer an easy way to determine where to drill a new hole for the antenna in '72. The next time my car is parked next to a '70 - '72, I will confirm that my antenna is in the exact same position as a factory antenna. That won't answer the question with absolute certainty, but if my antenna is out of place, that would at least suggest that the "no radio" cars left the factory indrilled/unpatched.

 

The existence of a patch on my car would have given the dealer an easy way to determine where to drill a new hole for the antenna in '72. The next time my car is parked next to a '70 - '72, I will confirm that my antenna is in the exact same position as a factory antenna. That won't answer the question with absolute certainty, but if my antenna is out of place, that would at least suggest that the "no radio" cars left the factory undrilled/unpatched.

 

The most likely cause of what you describe is bad speakers. I went through it on a very low mileage car. After speaking to a radio restoration guy he had me test the speakers and that was it. Prior to that I got an amp and borrowed a radio to no avail. The right speaker is easy to get to and the test is use a D battery, touch wires from a speaker and see if you get "noise" out of it. If you can get one good speaker to test your radio, all the better. The original radio requires 10 ohm speakers Not the 4 ohm "replacements" commonly available. If your speakers are bad the hardest part is replacing the left one.

 

The convector provides the final audio output for the radio. DS-501 transistors are available and, I believe, are being reproduced these days.

 

I bought my 76 with no radio and it was without speakers, any marks for where the antenna went and no signs of any repair where it might have been

 

First -- thanks to everyone for tips on diagnosing the radio problem.

Second -- I'm now curious about whether all Corvettes, even those ordered without a radio, had a hole drilled at the factory for the antenna. These three pictures won't answer the question, but I thought I would share. In the third picture, there is a rectangular metal plate where the antenna inserts through the bottom side of the deck lid. I wonder whether cars which left the factory WITH a radio had the same metal plate.


Antenna location





From underneath -- see rectangular metal plate. Also -- part number sticker?

 

Hi 71,
Yes, cars with the 2 optional radios had the plate.
It's what's being hidden by the antenna plate that will tell the tale.
What I've wondered about is how the hole was made originally. It's not a simple circle… it has an additional 'tab' on one side that the antenna base fits in so the base doesn't rotate.
A tiny detail… but curious!
Regards,
Alan

 

HI guys,
This post is already more than a year old, but still it could be worth sharing my experience with you. Most of the ideas on how to approach a radio that stopped from one moment to the other have already been shared. I have gone through the same process and got the radio to work again. It''s in the car since this weekend and it looks awesome. Only the antenna left to install and we're good to go. Anyone happens to know the exact drill hole location for the antenna mount?
If the radio still lights up than it does not short-circuit and chances are that the electrolytic capacitors are still working. Still be warned these will let you down one day and it's quite a fiddle to replace them.
In my case it turned out to be that amplifying transistors (DS 501) on both the convector and the external heatsink, had passed away. The DS501 is an antique part and not easy to find. It's a Germanium transistor (not silicon) and luckily, can be replaced by a small number of alternatives. The one I have used is a 2N173 which can be found on eBay. Same housing and same connections and it comes in baby blue. Great color.
Also, speakers are usually dead after so many decades so it's better to replace them.
Other than that, the radio is close to bullet proof so if you choose to have it fixed it will be worth it. I did all of it myself and total costs were just 12$ for the transistors plus some parts I had lying around.
Sending it me probably won't be worth since I'm located in Europe.
If it would help anyone, I happen to have the 71 stereo wiring diagrams. really old school stuff, but quite easy to understand if you a bit about electronics.