Hey everyone, today as I was taking my 63 out for the first drive of the spring, my radio cut out.  The radio turns off and on and still makes the light thump through the speakers when you do so, it just doesn’t produce any sound.  The radio is a AM only.  Does anyone have any experience with radio repair that could provide any advice?  Any input would help,  thank you.  

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is there a chance that your speakers are less than 10 ohm?  if so, you may have burned out your amplifier.  This is not fatal if you can solder and are willing to try it, I can walk you through it if that's the case. costs around thirty bucks but is EXTREMELY satisfying when you hear it play again.  

Other than that, the am set is very simple, so the only thing that I can suggest is to check the antenna cable.

I have torn some apart and repaired them, and they are old school basically bulletproof units, except the tuners.....  They are hand wound cardboard tubes that can decay and stick to the ferrite, breaking the wire and cutting off reception till it's repaired.  This usually happens when you are turning the radio channel.  The one on the far right is broken off on the picture below:unless it's the antenna, i'd suggest you get an AM FM that works and keep the am for parts.  The AM board and the amp are shared with the FM units, as well as the knobs, bulbs, belt/pulleys, and most of the face. 

Thank Mark for the reply.  I did replace the speakers with 8 ohm reproductions from a corvette supplier, I was hesitant but they assured me they wouldn’t be a problem.  

8 ohm will work,  there are companies advertising 10 ohm replacements that are actually chinese relabel 8 ohm speakers, and they work ok, i have used them because they fit the 66 stereo dash.  

I’m going to try investigating the coils, if they are damaged how would you go about repairing them?  Do they make a new replacement?  

It's not necessarily that a coil went bad, that's just the weak link in the system.   Is the radio out?   There are some simple things you can check before jumping into replacing things.

A little update on the radio repair.  I did a little more investigating, I noticed that the wonder bar would still seek properly which led me to believe my problem was with the amplifier circuit not the tuner.  On the circuit board there is a fusible resistor that had no continuity when I tested it.  I replaced the fusible resistor and the amplifier transistor and now the radio works again.  Hopefully it stays working, thanks to all the guys who chimes in with their advice.  

My guess is the transistor burned out causing the fusible resistor to blow.  The replacement resistor is a NTE105 sourced off of Amazon and the resistor I removed from another radio.

this is exactly what happens if you use low resistance speakers, or a speaker coil shorts out.  good job with it, you should do a write up on it, i'm sure it'd save a few people from replacing their dead radios with aftermarket units.
The resistor is also available out there, i have about ten left, but the ones i have aren't ceramic encased.  I believe i bought them from jameco or newark electronics.

make sure that your speaker wires aren't cut and shorting anywhere. and also, if aftermarket, have alook to ensure that the speakers don't have a short.  Once on this site, there was a short because of sloppy solder from the factory bridging to the negative post, but there could also be a short in the lead wires to the cone or the terminals may hit metal in the car.

anyway, good job.  feels awesome when the some comes out, don't it?

Mark would it be possible to buy 6 ohm speakers and fit some kind of resistor on the speaker wire?

I'm not good at all with electronics and the question is only academical.

yes, absolutely you can add a resistor.  The resistor has to be in series with the speaker circuit, not parallel, of course, and each speaker circuit would have to include the resistor, or have a ten ohm speaker.  
Resistance in series is calculated by adding resistance values, so if you have a 4 ohm speaker, you add a 6 ohm resistor to that circuit to make 10 ohm.  But if you have a voltmeter that is accurate enough, it's better to figure out the actual resistance of the speaker using volt drop because i no longer trust what is 'rated resistance' when it comes to protecting the amplifier circuit

On an side note to this excellent discussion I wish I could find someone that would want to take the say of 30+ am only radios that I have and go through and refurbish and/or use for parts. Some power up with no WonderBar function, some will not tune regardless. On some the wheels on back have just broken apart from heat. Aside from some quick pop open, clean out with air and tuner lube/cleaner, and replace a rear belt here and there I have had zero time to work with these. If anyone wanted a project and would like to source 10 or 20 of these I would make someone a deal. AND... I know there are some relatively easy things I could check/do to get some of these going but again I have ZERO time to commit to these.

If any interest email me atjasonedge@nc.rr.com



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