Radio for 1971
This is my first time on this website. I think I've found an origninal radio for my car. I have no convector and would like information, if anyone else has one. I'm not sure if the radio is mono or stereo. I think it is stereo because it has six wires in a ribbon. The model number is 31yfm1, the serial number is 1006964, product number 9341341. Is there any way to test the radio without a convector? Thankyou.
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Re: Radio for 1971
You must have convector box or will not work. The upper right face will be a stereo indicator light, and has a round plug for an adapter box in rear (for stereo only). Yes , you can bench test, using only 8-10 ohm speakers. -
Re: Radio for 1971
Welcome to our board !
Can't say for sure, but if my memory serves me correctly, this radio is from a 73 model. The 31YFM1 is the key. The 3 designates the model year. 1 tells us it is a Chevrolet unit. The Y tells us it is a Corvette unit. FM is the kind of radio and the number 1 indicates 1st in a series. ( My 73 has a stereo indicator light on the radio next to the FM band indicator )
Don't take this to the bank, but I believe this is correct. Hopefully somebody smarter than me chimes in.
Last edited by Tom H.; February 6, 2009, 05:37 PM.Tom Hendricks
Proud Member NCRS #23758
NCM Founding Member # 1143
Corvette Department Manager and
Specialist for 27 years at BUDS Chevrolet.Comment
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Re: Radio for 1971
Tom is correct - the 31yfm1 is listed in the 1973 Delco radio manual and only references back (no schematic) to a model 21VFM1 listed in the 6D-1972-1 manual. The 1972 manual refers back to the 1970 manual under 01VFM1. The 1971 manual refers back to model number 01VFM1 in the 1970 manual also. Most confusing... and that's why I always use an AR-78 Sams Photofact manual when working on that model (which you might find on Ebay ). Bottom line seems to be; if your radio has the 6 wire ribbon wire it is probably an early 74 model with a 73 model sticker.
A proper 71 radio will have a round black 9 pin socket in the back corner of the radio and green dial numbers. If there is a small round plug plugged into the socket, that is used to bypass the stereo output so the radio can play in monaural mode. For stereo, this socket connects to a 01VMP(A for A/C or H for HTR)1 stereo decoder unit which has a fat black cable and a 9 pin male connector which connects to the back of the radio.
There was no flat 6 wire (2 yellows/2 blues/2 greens) ribbon connector wire on the 1970/71 radio (or I've just not lived long enough to see one). Later radios had that. The 1970 radio had a 3 pin connector (blue/yellow/green) harness for a standard single transistor convector. The other convector (which connects to the second speaker) is mounted on the back of the stereo decoder box.
Sorry to add confusion James, too much info usually does that - especially when things changed on the production line. My conclusion, not having seen the unit, is that your 31YFM1 model doesn't appear to be correct for a 1971 because of the 6 wire ribbon. Maybe we can get a second opinion...? Hopefully I'm missing something.
The dual convectors, as well as the single ones, are regularly available on Ebay. Perhaps someone here will even have one stashed away.
Finally, the radio is probably functional James. If not, the C3 radios are rarely hard to fix.Comment
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Re: Radio for 1971
Just listed: a correct 71 that you can compare to your model.
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Re: Radio for 1971
James, here's a few photos of a convector for a stereo radio. When I was looking into original radios for my '74, I found the convectors for a mono radio to have one (1) diode, and the stereo models to have two (2). Hopefully this will help you identify what you'll need. RayComment
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Re: Radio for 1971
James-----
GM #9341341 is a STEREO radio uniquely applicable to 1973 Corvettes with the U58 stereo radio option. It was not used for other year Corvettes or for other Chevrolet models.
I believe this radio unit was used with an ADAPTER ASSEMBLY, GM #7312411, which included both the convector as well as the stereo adapter unit as a single assembly. I am not 100% sure about this, though. In any event, this radio requires a stereo ADAPTER unit whether, or not, that adapter is part of the convector.
Assuming that one acquires the necessary adapter assembly and convector (if it's not part of the adapter assembly), I think this unit could be used in a 1971. However, I believe at least the following would apply:
1) the installation would not be correct for a 1971 and would be discernably different, assuming that judging is one of your concerns;
2) the radio knob shaft length might be different from 1971 which might not allow you to install the 1971 style knobs;
3) the power connector from the car's dash wiring harness to the radio might be different, requiring "adaptation".In Appreciation of John HinckleyComment
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Re: Radio for 1971
Them tain't diodes... Day's bez Delco Remy made DS-501 germanium transisitors!Comment
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Re: Radio for 1971
If the dial #'s are white, it's a 72 and newer, if green, 71 and older. They should match color of guages. If its a stereo, even using a convector, the sound will very low as I have discovered ,install an adapter. if required and full volume will be acquired. Should only 1 speaker work (using balance control), then will need techinal repair to reciever and or adapter.Comment
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