1968 Corvette Radio Issues

[Joseph M.]

Hello,

My factory AM/FM radio worked up to the point before I recently had my dash apart for other repairs. My radio powers up but no sound comes out of the speakers. The antenna, power plug, and power amp connectors are connected. I did have to take the power amp out and it appears that someone replaced the power amp transistor during a previous repair of the radio. Is there a basic resistance check that I can perform on this power amp to see if it is still good? Also, can you provide me with a part number for this power amp transister where I could possibly purchase it possibly from an electronic store? In addition, if I wanted to go with a slightly bigger (ohm) speakers, would I installed a slightly different power amp? One last thing, a friend of mine told me that an updated replacement radio is available for my 68 that looks exactly the same from the front. Is that correct?

Thanks!

[Jack H.]

Re: 1968 Corvette Radio Issues

Yes, there's a basic go/no-go test for the DS-501 audio drive transistor that's outlined in any Delco Radio Service book, but you get what you pay for with this test (VERY gross functionality check)....

There's only one source for reproduction(s) of this dinosaur transistor (NTE) and the last time I looked they were pretty proud wanting something like $25 for their part!

On where to buy, go fire up your Google search engine. This is a 'classic' or 'specialty' component that few will have in stock.

On changing the xistor to 'match' speakers with a slightly different impedance profile, the answer is NO!!! The DS-501 is matched to the circuit topology it's embedded in by the radio itself. Upstream tone/volume controls were all designed centered on the specific characteristics of the DS-501.

BTW, why do you suspect the DS-501 is a goner? If during the R&R of the radio, you managed to improperly side-load the bananna plug on the antenna lead-in cable and open circuit it, you'll also have no output...

[Joseph M.]

Re: 1968 Corvette Radio Issues

Jack,

Thanks for the info on my radio. I think you may be right on the money about the antenna possibly being the problem. It seemed like when I wiggled the antenna cable on the side of the radio, I would get better reception. When I had the dash apart, I cleaned the inside of the antenna plug and I don't recall hearing it play after that. I was under the impression that if the antenna was unplugged I would just get static but it sounds like I'm wrong. Also, have you heard of a newer style radio that looks exactly like the original but with up to date electronics inside? I have seen some that look simular but the front appearance generally doesn't completely match.

[Jack H.]

Re: 1968 Corvette Radio Issues

I've seen a few ads from folks that 'gut' the internals of factory original radios and 'stuff' them with contemporary AM/FM/Stereo components. But, I have to question why anyone would go this route?

In the end, you've 'ruined' a classic Corvette radio chassis and wind up with AM/FM/Stereo only. Plus, without better speakers, what have you bought...no Tape/CD/iPod? Why not just leave the factory original radio alone and go fetch a rear compartment 'drop in' iPod type system?

On the problem perhaps being the antenna lead-in cable, I've seen that issue quite a few times. It typically happens in conjuction with a car's interior restoration where carpet is removed/replaced and those doing the work fail to handle the aged lead-in wire from the antenna with care.

The diagnostic is cheap/fast/simple. Walk in to WalMart and grab an off-the-shelf el cheapo replacement antenna with captive lead-in cable (less that $10). Now, remove the existing lead-in cable from your car's radio (easy and doesn't require pulling the chassis) and plug in the replacement antenna. Have a helper walk the antenna toward the rear of the car through an open door window while you sit in the cockpit and turn the radio on to assess a performance difference.

If all of a sudden AM station reception LEAPS at you, the original lead-in cable is probably history. Remember, the single conductor wire that's inside the cable is human hair thin! It doesn't take much abuse to crack it in one or more places...