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Discussion Starter #1 (Edited)
This just started yesterday. I recently re-capped my original AM radio and it has been playing great. Yesterday, I started hearing a motoring sound, not a whine, coming through the radio especially with the AC compressor on. Talking gets a bit distorted too. There is no noise or distortion when the engine is not running. There is a radio suppressor next to the voltage regulator that I substituted a .5 mf cap with but there was no change. Anybody got any ideas? Thanks, ,Cliff

PS: The noise may coincide with the repair I made yesterday to the amp meter wire near the starter solenoid. The noise is not a RPM whine and does not change with engine speed. Also, it was doing this before I snapped the mast off of my antenna which I also repaired. Reception is very good and I have adjusted the trim on the radio. FYI: I do not have the rear mounting strap on the radio. It was missing. Possible bad ground?
 

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Yes bad grounds are a culprit it seems more often than not when something has been either sitting a long time or recently disturbed.
 

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Discussion Starter #5
Yes bad grounds are a culprit it seems more often than not when something has been either sitting a long time or recently disturbed.
I tend to agree. I suspect a bad ground. Does the support strap on the radio act as a ground strap? Does the antenna base need to be grounded to the fender? Any other grounds I should suspect?
 

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Instrument Voltage Regulator. Little silver thingy screwed to the back of the instrument cluster that turns 12VDC into 5VDC but switching on & off at a constant rate.
 

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Discussion Starter #7
Instrument Voltage Regulator. Little silver thingy screwed to the back of the instrument cluster that turns 12VDC into 5VDC but switching on & off at a constant rate.
Hmm. Ok. Hadnt thought of that. Another thing I was thinking. When I got the car, the radio was a broken Custom Autosound that I tossed and replaced with this original . They had the CAS radio wired directly to the battery with an inline fuse so, I didnt know which wire the original radio was fed with. I just selected a 12 volt keyed source that wasnt being used behind the cluster and connected it there. I wonder if a different 12 volt power source would make any difference?
 

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Try using the actual Radio Suppressor that was meant for the car at the VR. You can buy them from Virginia Classic Mustang's (VCM) website.

There was also a Secondary Radio Suppressor and its hard to find today. It was located underneath the Wheel hub Dust cap and would work while the car was in motion.

1965 Mustangs also had a Radio Suppressor on the back of the Alternator. (Pictured Below) It was deleted on 1966 and later Alternators.

:eek:)

Tony K.
 

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Discussion Starter #10
Try using the actual Radio Suppressor that was meant for the car at the VR. You can buy them from Virginia Classic Mustang's (VCM) website.

There was also a Secondary Radio Suppressor and its hard to find today. It was located underneath the Wheel hub Dust cap and would work while the car was in motion.

1965 Mustangs also had a Radio Suppressor on the back of the Alternator. It was deleted on 1966 Alternators.

:eek:)

Tony K.
I am using the factory radio suppressor at the VR. I sub'd a .5 mf cap in its place as a test to see if the original was good or bad. It made no difference. I would expect a whine that would increase with RPM if it needed a suppressor at the alternator. Also, it doesnt matter if the vehicle is in motion. Just running while sitting will produce the noise.
 

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Maybe the new caps have no shielding? I have no idea. You might try some shielding material inside the radio...What have you got to lose...???

:eek:)

Tony K.
 

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Discussion Starter #12
Maybe the new caps have no shielding? I have no idea. You might try some shielding material inside the radio...What have you got to lose...???

:eek:)

Tony K.
Could be but there was no noise for several weeks after I recapped it. Its going to be fun figuring this one out.
 

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Could be the Antenna too maybe... Try using one of those "Hide away" Antennas and see if the humming goes away.....

If not, Maybe the car's ignition system?.....Move over to Pertronix??!??....lol.... Shooting in the dark here....lol....

:eek:)

Tony K.
 

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Bad solder joint on one of the replacement caps?

Btw what caps did you use? And lessons learned? I need to recap my am/fm
 

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Discussion Starter #15
Bad solder joint on one of the replacement caps?

Btw what caps did you use? And lessons learned? I need to recap my am/fm
A bad or cold solder joint would produce the noise with just the key one and engine not running.
Ive been restoring antique tube and early transistor radios for about 25 years so I have accumulated a huge stash of new capacitors and resistors. I also bought all of the ones my local Radio Shack had when they were closing. There is nothing mysterious about re-capping these radios. Its pretty straight forward. Go slow, match the value on the original cap as close as possible. Its OK to go slightly higher than the marked value but dont go below that number. At least 1 cap will have 2 caps in one can. Those are electrolytic capacitors and the most important. Before you remove that cap, note the orientation of it and study the information that is stamped on the can. I have not recapped a FM car radio so, I would expect several more capacitors. Is your radio currently working OK ? If so, I would leave it alone until the volume or clarity starts to diminish . Good luck!
 

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I too lean towards a bad solder connection. The modern solder is crap. Pretty much, you have to use an external flux and even then the connection could be iffy. Not so much of a problem with surface mount components as they have very little mass and produce almost no moment in a vibratory environment. The big old axial caps are a different story. Couple that with the vibratory environment of a vehicle and you have the recipe for electronic mayhem. I jealously guard and accumulate all the 60/40 I can find.
 

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@;
A bad or cold solder joint would produce the noise with just the key one and engine not running.
Ive been restoring antique tube and early transistor radios for about 25 years so I have accumulated a huge stash of new capacitors and resistors. I also bought all of the ones my local Radio Shack had when they were closing. There is nothing mysterious about re-capping these radios. Its pretty straight forward. Go slow, match the value on the original cap as close as possible. Its OK to go slightly higher than the marked value but dont go below that number. At least 1 cap will have 2 caps in one can. Those are electrolytic capacitors and the most important. Before you remove that cap, note the orientation of it and study the information that is stamped on the can. I have not recapped a FM car radio so, I would expect several more capacitors. Is your radio currently working OK ? If so, I would leave it alone until the volume or clarity starts to diminish . Good luck!
Thanks, I have done a fair amount of electronic work over the years. My current radio is fuzzy, and the sound breaks up as the volume increase. The reception is poor too.
 

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Discussion Starter #18
Wouldnt you guys agree that it would have the noise without the engine running if it was a radio issue? Im not opposed to pulling the radio and rechecking it but, it doesnt make sense to me.
 

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Wouldnt you guys agree that it would have the noise without the engine running if it was a radio issue? Im not opposed to pulling the radio and rechecking it but, it doesnt make sense to me.
Not if engine vibration was affecting it. My first though though is a bad ground somewhere causing feedback in the electrical harness.

The rear strap is important for supporting the radio, but shouldn’t affect the sound.
 
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