Original Radio in Back into 1970
I installed my original radio back into my 1970 only to find out it is not working. The plug on the drivers side has the yellow power 12 volt facing the rear of the car is this correct? I am getting 12 volts to the radio, is there any other tests I can do? How do you test out the heat sink on the passenger side? Any ideas?
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Re: Original Radio in Back into 1970
Les,
I hope that you have tested the speakers. When I purchased my 71, I assumed the radio was not working since I could not get even the slightest sound out of either dash speaker. Radio was working fine. The speakers were toast. -
Re: Original Radio in Back into 1970
Going back to my car stereo days here. A quick easy way to test a speaker(s) and the wires is to take a 1.5V battery and apply it across the speaker wires (or perhaps to the jack holding speaker wires). You should here a "popping" sound coming from the speaker. If the speakers are fine, the radio is next. The finals are usual suspect there.
JeffComment
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Re: Original Radio in Back into 1970
Les, there are 3 terminals on the drivers side of radio, the one towards engine is the radio light, middle terminal is ground and the last towards rear of car is the power for radio. Seems like you did have power source correct as you described, if light is working then you have a ground also, the heat sink must be good for the radio to work at all. The last c-3 radio repair cost me about 125.00 if all else fails. Do if not already tried, move slide am/fm in small incriments and listen for a sound, radio will not work until in proper am or fm position, also try another antenna even if its not for a corvette. I hope this helps. SteveComment
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Re: Original Radio in Back into 1970
Good instructions Steve, "the heat sink must be good for the radio to work at all." That is the final amplifier. In my days as a bench tech., this was a culprit in many OEM radio repairs. The transistor would be toast...
JeffComment
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Re: Original Radio in Back into 1970
And how do you bench test a heat sink? Then we'd have an idea on all three component portions.Comment
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Re: Original Radio in Back into 1970
Very simple (IF you're an electrical engineer/tech)! You whip out your transistor curve tracer, connect this transistor (I believe it's a DS-501) and sweep the sucka.
What, you're not an EE/tech and don't have that kind of test equipment? Then, you're stuck with the 'go/no-go' tests described in the Delco Radio manuals that use a conventional multi-meter on resistance scale.
That'll tell you if the xsistor is COMPLETELY blown, but it won't tell you if she's been 'hit' and is among the walking wounded...Comment
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Re: Original Radio in Back into 1970
BTW, the 'heat sink' is the metal platform the transistor is mounted onto. They rarely 'fail'....Comment
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Re: Original Radio in Back into 1970
Yes Jack, I've used that too, we called it a "tracker". It makes a checkmark in the scope when it has a good semicondcutor junction. I never liked that machine and preferred testing bias voltages to tell me if good or bad. I used to see blown finals all the time at the stereo shop I worked at during college, all different manufacturers of course. (BTW -later on I worked for Motorola for 20 years ) As for the other discussion....
I'm not familiar specifically with the 1970 corvette radio finals but imagine it can't be much different than the others I worked on. I used to signal trace up to and through the amplifier(s) with an oscilloscope but that's not practical for most people. Truthfully I never removed the AC ducts in my car to look at it. Most car radios have the finals with heat sink on the back of the radio chassis. My assumption for the Corvette is the "heat sink" is separate from the radio chassis due to lack of space behind the radio when installed.
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JeffComment
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