Radio Question

[Doug Flaten]

Perhaps Jack or one of you electronics experts can help. I have a stock AM radio in my 1966 Mustang. After about 10 minutes the reception starts deteriorating and gets increasingly "crackly". After 20 minutes to 30 minutes the reception totaly fades out and the radio stops working. Once cooled down or off for a while I can turn on the radio and repeat the sequence. It must obiously be heat related on some component. Is it some kind of tube or is it a power module of sorts? I don't know if they were solid state electronics in the radio at that time. I do know it is not as bulky as my Wonderbar. I am wondering if it is worth repairing with a component or replace the old thing. Just wondering where to start looking.
Thanks,
Doug

[mike cobine]

Re: Radio Question

Sounds like the power transistor is heating and going out. While many are different numbers, they were really a very generic type and were easily replaced back then. Since a lot of that has decreased in later years, I'm not sure of the availability today, but I would think any radio shop should be able to fix it easily.

However, that is a repair shop and not a Circuit City, Best Buy, etc. store.

The repair shop may be more rare than the part. Looking in the telephone book may bring up one or two TV-Radio repair shops if you are lucky.

I wouldn't think it would be much, since it is a relatively simple fix. Price of the part plus an hour tops.

And a lot depends on if you want the Mustang original or with a new AM-FM CD player. I don't think you can find cassette players anymore either, not of any quality.

[Jack H.]

Could be any number of issues...

First, YES solid state components were in use in radios by 1966! They can and do 'age' but this is typically the result of electrical overstress. By far the main 'culprit' in this process is the aging of amplifier stage, DC blocking, 'coupling' capacitors which were then often of wax-foil construction. These are prone to breakdown of the wax used to serve as a dielectric and insulate the internal foil storage plates from each other.

When the wax ages, the capacitor begins to 'leak' internally and the capacitor's ability to block DC current flow goes 'south'. Then, the amplifier stage downstream begins to overload/saturate and all kinds of 'funnies' result.

Any competent local radio/TV repair shop can get schematics (HW Sams is the world's prime source) and trouble shoot and repair the radio for you. BUT, bench fees are going to run something like $50/hr for labor + parts. Since Mustangs were produced in substantial qty, if might be cheaper/faster to call around to your local scrap yards to see if you can get a 'fresh' replacement radio (typically a $25 yard item) vs. have your original radio repaired. The decision is yours....

[Gerard F.]

Re: Radio Question-Also

Doug,

To add to other responses, if the speaker was changed to heavier speaker, it will cause overheating of the main transistor and the symptoms you describe.

Same thing happened to my 67 Corvette AM-FM. After getting the schematic and service manual excerpt (try justradios.com)and the transistor number, I was able to get a replacement transistor online from Radio Shack. With a correct speaker, the radio works like new.

Jerry Fuccillo
#42179

[Doug Flaten]

Re: Radio Question

Thank you all for the advice. I seem to remember reading something about the speakers years ago. Anyway, I did replace the speaker 15 years ago and it has worked well since then. An upgrade may be in order.
Doug