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Old 06-26-2004, 01:01 PM   #1
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Univolt HUMMING!

I have a 1984 Excella and the original Univolt system has a noticeable hum when connected to the 110V AC that bothers me. Is this normal or is this a result of aging parts, like capacitors or the transformer?
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Old 06-26-2004, 01:03 PM   #2
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My '67 hummed. I don't think it is something to worry too much about...
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Old 06-26-2004, 01:20 PM   #3
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The reason your Univolt hums is because the varnish in the transformer has become brittle and allows the plates of steel to viberate causing the noise u hear.Its really more annoying than anything,You can take it apart and re-coat the transformer with varnish it if becomes too annoying.
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Old 06-26-2004, 06:00 PM   #4
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Thanks

Thank you Tradewind for that advice.
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Old 06-29-2004, 08:03 AM   #5
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Quote:
Originally Posted by 71tradewind
The reason your Univolt hums is because the varnish in the transformer has become brittle and allows the plates of steel to viberate causing the noise u hear.Its really more annoying than anything,You can take it apart and re-coat the transformer with varnish it if becomes too annoying.

Has anyone actually done this?

Did it work?

In hindsight, would you do it again?
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Old 06-29-2004, 09:11 AM   #6
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Your Univolt hums because it is a ferro-resonate charger. The technology is very old. I have worked on this type of charger that dates back to the early 40's. They hum is because the circuit sets up the transformer in resonance, hence; ferro (iron core) resonance.
If you want quiet you will have to go the the newer switched mode supply which raises the resonate frequency up in to about the 200kHz frequency range where you can't hear the components ring.
Another advantage to changing out your old Univolt is the newer chargers have multiple charge modes which help to take better care of your battery banks. (Last Longer)
I changed mine out and am happy as a clam that I did. Quiet, and my battery does not boil dry.
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Old 06-29-2004, 09:15 AM   #7
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Originally Posted by 87MH
Has anyone actually done this?

Did it work?

In hindsight, would you do it again?
I have not done this, but the idea has merit. But, between what I understand about transformers, and what I have read about Univolts in general, there will always be a hum.

I believe the individual plates which make up a transformer's core are "varnished" before assembly. Disassembly will be a chore. IMO, the amount of hum reduction would probably not offset the labor involved to perform the task.

Tom
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Old 06-29-2004, 10:34 AM   #8
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On my 75, during the day I really don't notice it, at night I turn if off.

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Old 06-29-2004, 11:53 AM   #9
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Inteli-Power 9100 Converter

Here is a link to Inteli-Power 9100 Converters which has a link to a lay-man's tutorial on the various types of converters:

http://www.progressivedyn.com/rv_power_converters.html
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Old 10-11-2004, 04:28 PM   #10
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Gary
Read your thread with interest. Just purchased a 1976 Tradewind and was wondering about the hum. What newer units do you recommend and is it a difficult task to replace it?

Thanks for your time

Ivo

it is a ferro-resonate charger. The technology is very old. I have worked on this type of charger that dates back to the early 40's. They hum is because the circuit sets up the transformer in resonance, hence; ferro (iron core) resonance.
If you want quiet you will have to go the the newer switched mode supply which raises the resonate frequency up in to about the 200kHz frequency range where you can't hear the components ring.
Another advantage to changing out your old Univolt is the newer chargers have multiple charge modes which help to take better care of your battery banks. (Last Longer)
I changed mine out and am happy as a clam that I did. Quiet, and my battery does not boil dry.[/QUOTE]
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Old 10-11-2004, 04:43 PM   #11
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Originally Posted by drivo
...and is it a difficult task to replace it?
It is an easy, wire-for-wire replacement. Many people will probably offer a much better, care-free replacement.

I, on the other hand, am someone who would milk the cow in the morning for fresh milk. I enjoy the challenge of running the Univolt while not overcharging the battery.

Just another point of view,
Tom
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Old 10-11-2004, 06:39 PM   #12
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they hum 'cuz they can't sing!

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Old 10-11-2004, 07:25 PM   #13
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Mine hums sometimes.....I thought the thing had a fan and cooled itself off once in a while.
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Old 10-11-2004, 10:26 PM   #14
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I guess you now have an Airstream & a hummer!
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