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Old 07-15-2003, 12:19 PM   #21
3 Rivet Member
1975 24' Argosy 24
Burlington , Ontario
Join Date: May 2003
Posts: 109
Power Supply Hum (Buzz)

The reason for the HUM is that the AC electricity running through the windings in the transformer causes the lamination plates to vibrate at 60 cycles and thus it hums.
Because of the magnetic field

The answer is to move the transformer. SORRY

Other than taking the transformer out and binding the plates and dipping in a varnich (and that may not help) I can only sugest that two sticks of dynamite or the same can cure it. Or don't plug into external AC

Rae Baker
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Old 07-15-2003, 01:29 PM   #22
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1971 27' Overlander
Join Date: Nov 2002
Posts: 632
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Hummm at 50 hz

My magnetec make too a noise like you but in 50hz and I think the noise is the same;
To attenuate it, I've put a polystyren plate under the univolt because it was fixed on a wood plate on the furnace tunnel and , in this way , you really heard the sound vibrations from there, in the bathroom.
With the ploystiren plate, the humm is very light, nearly inaudible.

If that can help you...

the prior owner has equiped a switch too, to stop the hummm during the night surely.

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Old 07-15-2003, 06:42 PM   #23
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I never even heard my univolt at all while I was plugged in at KOA. It's under the right twin bed which my youngest son sleeps on. He never said anything about a hum keeping him awake. Now that makes me curious as to wether it's even working! I will check soon...I really appreciate all the brainstorming here, although it may get expensive
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Old 07-16-2003, 07:23 AM   #24
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1975 24' Argosy 24
Burlington , Ontario
Join Date: May 2003
Posts: 109
Power Supplies for Air Streams

Not all but many are merely an AC transformer that have voltage doubling and a diode arrangement to supply 12 volts to the trailer and charge the batteries.

A 55 Amp unit is capable of delivering up to 55 Amps but does not push 55 Amps through your battery.

It is like having a gallon bucket and taking out only a once at a time or what you need. one ounce , two , or more, but capable of 55 amps if needed.

Your battery has an internal resistance, and this is low when the battery is used up and the current from the charger will supply enough voltage and current to charge the battery. As the battery is charged the internal voltage will rise in the battery and the resistance increases, and limits the charging current. Once fully charged the voltage in the battery is the same as the charger and little if no more current is delivered to the battery.. An automatic limiting system.
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