1973 Correct Corvette Stereo Radio

[Gary C.]

I have a January build 1973 Corvette that has the radio amplifier and speakers installed but the radio is missing.
According to the internet the amplifier under the dash is from a 75. I am trying to find the correct radio to match this amplifier.
However I am not sure that this two transistor amplifier correct for 1973?
Thanks for help,
Gary

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[Harmon C.]

Re: 1973 Correct Corvette Stereo Radio

The large amp is stereo the small amp is mono. I think your pic is the large stereo amp in a 73.

[Guy F.]

Re: 1973 Correct Corvette Stereo Radio

Correct.

The AM/FM Stereo (U58) convector has 2 power transistors and the AM/FM Mono (U69) has one power transistors. Yours is a convector for a U58 radio. It is also referred to as the "large" convector or "large" amp as mentioned by Lyle.

Can you read the date code(s) on the transistors? They should be stamped in yellow ink "DS-501" and then a 4 digit date code underneath, (YYWW) format. Painted black fins tells me it is generally a '73 or early '74 convector. Later convectors ('74-76) had natural fins, but I have seen exceptions.

A 1973 U58 radio would have a service model number of "31YFM1"
A 1973 U69 radio would have a service model number of "31YFP1"
As a reference, a 1975 U58 radio would have a service model number of "51YFM1", although visually identical.

Service Model numbers, serial numbers, FCC part numbers, plus a whole bunch of patent data are on a printed label found on the side of the radio. many labels are gone on restored radios.

Original working radios are out there. Here is one. Not cheap. Keep looking.

https://www.ebay.com/itm/Original-C3-1968-1976-Corvette-Oem-Delco-Am-Fm-Radio-Working-Condition/123873916909?hash=item1cd775f7ed:g:LpUAAOSw6gNdUzug

BTW I have trouble believing an advertised radio "works" or has been "tested and works great" when they are selling it without a convector. The radio will power up but not emit sound without the convector.

thank you,

[Jimmy P.]

Re: 1973 Correct Corvette Stereo Radio

Gary,
To help narrow your search down, you should only be looking for a 72-75 Delco Stereo Radio. If you notice in Guy's ebay link above the seller lists the radio as a 1968-76 radio. Yes, the pictured radio is correct for your 73. Keep in mind that the earlier 68-71 radios have greenish tint colored numbers on the dial to match the gauges for those years. And of course the knobs are different. The 72-75 radios have the white numerals to match the gauges and the different knobs as you probably already know.
Actually, a 76 Delco Stereo Radio would also work (same face/knobs) but if you look closely at the dial face you'll notice the earlier C3 radios thru 75 have the word Delco in script on the lower right side of the dial. The 76 radios have the DelcoGM logo in block letters with a square around it on the left side of the dial.
Top photo below is from a 76 and the lower photo is from a 72-75.
Hope this info helps.

[Gary C.]

Re: 1973 Correct Corvette Stereo Radio

Correct.

The AM/FM Stereo (U58) convector has 2 power transistors and the AM/FM Mono (U69) has one power transistors. Yours is a convector for a U58 radio. It is also referred to as the "large" convector or "large" amp as mentioned by Lyle.

Can you read the date code(s) on the transistors? They should be stamped in yellow ink "DS-501" and then a 4 digit date code underneath, (YYWW) format. Painted black fins tells me it is generally a '73 or early '74 convector. Later convectors ('74-76) had natural fins, but I have seen exceptions.

A 1973 U58 radio would have a service model number of "31YFM1"
A 1973 U69 radio would have a service model number of "31YFP1"
As a reference, a 1975 U58 radio would have a service model number of "51YFM1", although visually identical.

Service Model numbers, serial numbers, FCC part numbers, plus a whole bunch of patent data are on a printed label found on the side of the radio. many labels are gone on restored radios.

Original working radios are out there. Here is one. Not cheap. Keep looking.

https://www.ebay.com/itm/Original-C3-1968-1976-Corvette-Oem-Delco-Am-Fm-Radio-Working-Condition/123873916909?hash=item1cd775f7ed:g:LpUAAOSw6gNdUzug

BTW I have trouble believing an advertised radio "works" or has been "tested and works great" when they are selling it without a convector. The radio will power up but not emit sound without the convector.

thank you,

I see on that radio on eBay they have cut the connector off which connects to the two transistors!

[Keith K.]

Re: 1973 Correct Corvette Stereo Radio

All good comments, but I would say that the first question you need to answer is: are the 2 power output transistors (DS-501s) on your convector (heat sink) good or bad? These are very old technology germanium PNP power transistors that haven't been made in many years, and they can go bad. Replacements are very difficult to find! If you buy just a radio head unit that is tested good, and connect it to your convector which has a bad output transistor - you don't have a solution. Try to find a complete radio that has been tested as working properly.

[Gary C.]

Re: 1973 Correct Corvette Stereo Radio

I believe 2N277's are a replacement. for the DS-501's.

[Guy F.]

Re: 1973 Correct Corvette Stereo Radio

I see on that radio on eBay they have cut the connector off which connects to the two transistors!

Exactly! Hence my earlier comment in my post.

"BTW I have trouble believing an advertised radio "works" or has been "tested and works great" when they are selling it without the convector. The radio will power up but will not emit sound without the convector."

There is no convector advertised with that radio for sale on ebay. It is however, a 1973 U58 radio, service part number 31YFM1.

I agree with Jimmy's comments. U58 from 1973, 1974, and 1975 all have the same exterior appearance. The head unit and the convectors are the same. Service part numbers are different on the head units, and date codes on the power transistors are different, but you can't see any of that when it is installed. 1972 has the same exterior appearance as well, but it employs a separate "multiplex adapter". Multiplex adapters are topic of another discussion.

I agree with Keith's comment suggesting you find a complete radio with a convector, with intact wiring harnesses and plugs, that has been tested and is working properly.

Thank you,

Guy

[John S.]

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[Mark E.]

Re: 1973 Correct Corvette Stereo Radio

The stereo in my '70 has failed twice in the past 30 years. So I'm wondering about the merit of finding an old replacement that might work or patching the circuitry in the current one.

Would replacing the guts of the original with modern electronics be a better choice?

[Gary C.]

Re: 1973 Correct Corvette Stereo Radio

It wont be "Original" then, but we are getting to stage when there will be no AM or FM transmitters and it will be all digital so perhaps you are correct. Then we will fit a set of side pipes and leave the radio off!
Thanks everbody for your input.
What I needed to confirm was the 73 was a different radio to the earlier 72.
The 73 went to the new two transistors on a heatsink under the dash and the FM multiplexer was inside the radio.
Which is different to the 72 which had one output transistor on the rear of the radio and another mounted under the dash and the FM stereo multiplexer in a separate box also under the dash.
Thanks,
Gary
Perth Western Australia