I'm getting a rythmic thumping/pulsing noise from my OEM 1964 AM radio....

Doesn't matter what frequency it's set to, it's the same noise.

It's not interference from anything else, as it does it when the engine and everthing else is off and it is running on battery.

I think it may be temperature or humidity related as it's cold and wet now in Southern California.

Sometimes turning the radio off will fix it.

Eventually it seems to go away if the radio has been on for awhile.


Something in the back of my mind thinks there's a vibrator inside for high voltages. I don't know if that's for old solid state or old vacuum tube radios.


Anybody know of a site that has a diagram and writeup on how these old radios work?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I used to have a 64 Valiant factory service manual and it actually gave the wiring diagrams for the radio in it.

Have you tried a noise suppressor on the coil? Could be the capacitors in the radio crapping out after 44 years.

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Casually looking for a Clifford hyperpak intake for cheap.

Engine is off......

Only thing on is the radio....

Thumping frequency is about 2/second...


Still have the wiring diagrams?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Nope sorry. The shop manual went with the car when I sold it. Try your local library, they might have a shop manual in the reference section. That's where I got the one for the 64 Valiant. I spent a couple hours and a few rolls of quarters in the copy machine at the library.

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Casually looking for a Clifford hyperpak intake for cheap.

I have the 1965 FSM, and it doesn't have a diagram for the radio.....



Must have quit putting the diagram in in 1964 then.


(yes, I have a 64 car and a 65 FSM; figured close enough...)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I've had great success buying Sams Photofact manuals for the Mopar factory radios. I seem to remember that I bought them from Tannenbaum; they were in perfect unused condition and have the schematics and photos of the board layout; well worth the money.

You need to know the *exact* # of the radio, usually a sticker glued to the case. The car info doesn't help - you need the radio # to get the right manual. Even though my radio was made by Motorola, that company never even responded to my inquires.

I've found that those radios were fairly easy to fix *unless* the output transformer was fried - I was unable to locate a source for new ones. The most common parts I saw fail were electrolytic capacitors and the power transistor; I'd expect that your symptoms are caused by the former.

My '64 radio does the same. The frequency stays pretty constant. The engine status - on or off - makes no difference. If the car interior is cool, the radio chatters. The pulse width increases with time and temperature so that when the car has been driven long enough, I can actually listen to the music/talk. In the summer, there's not much of a problem. In cold weather, it takes a long time. Eventually, the threshold temperature of this problem got high enough to bother me in the fall and spring as well.
It's not the speakers - checked by substituting known-good speakers - or the power to the radio - nice and steady.

I just haven't taken the time to dive into the radio itself.

Right now the factory radio is there for looks. Its round pushbuttons and "Valiant Transaudio" markings look right, when nothing else would. I put a cheap AM/FM/USB/SD radio in the glovebox. Fewer critical moving parts than on a CD player. My only complaints about it are:

1. I actually use my glove box, and need the storage space back.
2. With a non-retractable shoulder belt, it's a long reach to some of the buttons.
3. I need to mount it deeper or get a shorter thumbdrive, so I can leave a drive in the player with the glovebox door closed. Hmmm ... maybe an "L"-shaped USB adapter?

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Most likely (from the sound of it) you have a bad electrolic capacitor. It is leaking electrically. The electrolyte in it has dried out and it will not hold a charge any more. The symptom is call "motor boating". You do not have a vibrator-those went out around 1956. It needs repair.

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

My 64 Valiant had a neat factory option of a rear speaker that had a variable delay resistor on the dash. It created a fake "stereo" or "surround sound" and actually sounded pretty cool. I forget the factory name of it, but the wiring diagram for that was in the FSM too.

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Casually looking for a Clifford hyperpak intake for cheap.

Radio Speaker Reverberator

Got the wiring diagram for that.................

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That's it! It was a pretty neat little device that sounded good too. Dang, I wish I still had that car. My first project car ever- a 64 Valiant Signet.

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Casually looking for a Clifford hyperpak intake for cheap.

My 67 GTX had the reverb in it-sound was great, until the news can on LOL.

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

It's pretty common that the 5V electro-mechanical voltage regulator can cause all kinds of noise in old radios (it comes when the arm moves over the coil).

Its the radio-it needs repair. The dash voltage regulator makes a "hash" sound. The sound you are describing is called "motor boating". You have a bad cap. Might be in the AGC/AVC circuit or one of the audio coupling caps. If you look inside the radio and you are lucky you may see a cap with a white powder on it. That would be the bad cap. Some have a polarity to them and some do not. The value of the cap is important but not its voltage as long as it is equal or more than than the original volts. 10 micofarads at 10 volts can be replaced with 10 microfarads at voltage of 25 volts. Or 50 volts

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50 chrysler,54 Plymouth, 64 Valiant conv 4 speed, 66 Valiant V8 wagon, 70 Challenger R/T 440+6 conv 4 speed,80 Colt, 98 Neon ACR,84 Honda V45 Magna
Taking care of 57 300C conv,48 T&C conv. Missing my 67 GTX and 36 Ply coupe

The noise has a good chance of being the dash voltage regulator. It cycles on and off at a relatively rapid rate, and often the radio picks it up as a basso profundo "pop".

What can you do about it? a properly located capacitor will help, and if you're lucky, you might be able to fit in one of those electronic replacements for it.