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Old 01-23-2006, 03:13 PM   #1
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Wink Humming Univolt

Hello to all of you airstream owners,

Just got our '71 airstream 27" from the States! We will tell the whole story later on,
but first of all, YES again !, another terrible humming univolt Triad Utrad TU 345A (installed somewhere in 2001).
Read this good, and if someone knows the solution, let him speak, please.
We are in Holland, Europe, and our electricity is 220V/50hz, we want to keep
everything running on 110V, and bought a very powerfull 'transformer' (forgot the propper english word)that does that.
Here is our question: since we are on 50hz, and this Univolt 'wants' 60hz, could it be that because of that, it hums like it's life depends on it? even with the radio turned on, you can still hear it humming!
Can this be fixed with some simple adjustment, or do we have to throw it away, and get another one, and are there univolts that will run OK on 50hz?
I know there have been lots of questions about this type of Univolt, but we could'nt find the answer to our question...
One thing we allready tried, and that was 'swapping' the positif and negatif wires, but no luck there !
Hope some of you guys have the knowledge to help us enjoy this practical new Univolt..
Thanks for your support.
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Old 01-23-2006, 03:45 PM   #2
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I am not sure if your UniVolt is new or not.
I do not recall any that are still made. Maybe I am wrong. Not sure.
I do know that you can get them to "hum the same tune" on 110 V/60 Hz.
I replaced mine with an IntelliPower 60 amp unit. These are readily available here in the states. Not sure where you could pick up something for yours in 110 V flavor in Europe.
If you can get a 220 VAC to 12 VDC over there I would make that swap.
Just my ten cents. My two cents are free.
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Old 01-23-2006, 09:34 PM   #3
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Hi, Holland,

Mine hums like it's expecting boredom, but it's still putting out 13.75 volts. I sleep on the other end, and the stereo/8 track still works... I just turn up the music and let it humm, humm, humm. The batteries are still 1979 technology, so why get fancy charging?

Lamar
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Old 01-24-2006, 03:00 AM   #4
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As a general rule it may be unsafe to operate 115V 60Hz rated appliances at 115V 50Hz. Operating 60Hz appliances at 50Hz may result in excessive heat buildup in transformers or in certain types of electric motors. The concern is mostly for inductive devices. Resistive things like heaters do not care.

Transformers designed for 60 Hz operation can overheat and sometimes burn up when used in 50 Hz circuits. Check to see if the Univolt is rated for both 50 and 60 cycles. If it is rated only for 60 Hz (the nameplate info doesn't state anything about 50 Hz power input) then it should probably be used only for 60 Hz.

Also, It may be important to see what voltage you are feeding it in the first place. While a transformer can be run under or over the rated voltage (with some limitations) the amount of voltage fed to a transformer can change the noise they produce. Generally the higher the voltage, the louder the transformer.

Lastly, there is a little beast called harmonics which could come into play here. The secondary of the transformer, rectified and coupled to capacitors could produce harmonic interference at the lower frequency that would not be apparent at the proper frequency.

Univolts are noisy beasts in the first place but if yours is uncomfortably loud, it may be telling you to beware. The sound produced by a transformer comes from the physical movement of parts windings and to limited extent the core as well as the case. Louder than normal sound could be the windings groaning under the strain of increased current flow. It is normal for transformers to make some noise but not too much noise.

So check the voltage coming in and if it is within 10% of 120 volts, that is normal. You may have to look powering your rig with a solid state unit like an Intellipower or equivalent. Also, if you can reach the Univolt, feel if it seems really warm or even smells hot. If it smells hot at all, you should be prepared for a catastrophic failure of the unit. Heat is a transformers worst enemy because it breaks down the insulation in the windings. The windings can short out and the results could be real ugly.

Best case scenario is that the Univolt is a tough old beast and while complaining may take the beating without any damage. In any event you have a few things to look at and determine for yourself if it is O.K. or not.
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Old 01-24-2006, 07:28 AM   #5
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Hello,
The Univolt was new in 2001, so that's not old, is it?
And the Univolt doesn't get hot at all,and no smells are noticed. Another thing is, that it doesn't charge the battery, when connected to city power, there is 6-12volt coming through the chargingwire though....,
Does that tell anything?
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Old 01-24-2006, 07:39 AM   #6
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That is a new unit so I suspect the problem is elsewhere.

I could guess one of a few things. One being that it is underexcited by operating at a lower frequency but I kind of doubt that.
Only one way to tell for sure is to somehow give it 60 Hz. If all is well then that is the problem. But I am starting to suspect the problem may be a faulty univolt.
The low voltage is a sign that perhaps one of the diodes is blown.
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Old 01-24-2006, 11:58 AM   #7
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KC and the Sunshine Band

Quote:
Originally Posted by SafeHarbor
Hi, Holland,

I sleep on the other end, and the stereo/8 track still works... I just turn up the music and let it humm, humm, humm.

Lamar
I bet you still have a stack of 8-track tapes, which includes at least one KC and the Sunshine Band tape??

Mitch
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Old 01-24-2006, 01:09 PM   #8
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I replaced my univolt a couple years ago but still have it. Can they be rebuildt?
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Old 01-24-2006, 03:22 PM   #9
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Thanks Buttercup,
Don't call me stupid, I'm Dutch, but this diode, is that one of those tiny glass fuses behind the Univolts lid ? and if so, I assume when it is brown/black that shows when it's not OK?They all look christal clear, to me.
Or are you talking about something completely different? We don't have the manual to this Univolt, wich makes it a hard job!and both of us are totally bums when it comes to electricity...
Thanks so far, Kai
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Old 01-24-2006, 09:27 PM   #10
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Quote:
Originally Posted by Holland
Thanks Buttercup,
Don't call me stupid, I'm Dutch, but this diode, is that one of those tiny glass fuses behind the Univolts lid ? and if so, I assume when it is brown/black that shows when it's not OK?They all look christal clear, to me.
Or are you talking about something completely different? We don't have the manual to this Univolt, wich makes it a hard job!and both of us are totally bums when it comes to electricity...
Thanks so far, Kai
Sorry I missed this one. Yes, those are fuses and the fact that they are not brown is not really the best indicator that they are good but a good visual at least.
The diodes are something else not serviceable so don't worry about that. I am curious about the voltage readings you got. Could you tell me more? What 12 volt readings do you have???
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Old 01-25-2006, 04:42 PM   #11
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Hello Buttercup,

We are going to call in the help of an electrician, to sort this out, as our voltage reader isn't a state of the art one..., if we get stuck somewhere, we will get back and call in your advice again, think it will be after the weekend.
Till then!
Thanks, Kai
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Old 01-26-2006, 11:27 AM   #12
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Please do - I would be interestred to see what you find.
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