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Humming noise
Yahoo Message Number: 149383
Hello everyone,

I'm new here. I'm also new to RVing and Lazy Daze. I'm still in the learning phase and I appreciate all the help I can get.

I have a 1990 26.5 ft Midbath Lazy Daze. I got it in July in preparation for my fulltime RVing.

I've been hearing some humming/buzzing noise underneath the kitchen sink area that's gotten progressively louder. In the beginning, the noise would cycle (come on and off), but now it's constant. I believe that's where the RV converter is located. I'm hooked up to a shore power. The noise stops when I unplug.

I also have what I believe to be a weak battery, because the other day, my generator wouldn't start. I was running it as a routine maintenance because I was told if I don't run it once every 2 weeks-month or so, it would stop working.

When I used the search function to see if anyone had a similar problem, I was not successful. I might've not tried harder though.

The noise is starting to get to me, so I greatly appreciate any thoughts. Thank you.

Clara
Re: Humming noise
Reply #1 –
Yahoo Message Number: 149384
Clara, you're probably right in thinking that the buzzing noise is coming from your converter. Your 1990 midbath has a Magnetek 6345 converter--an old design that uses a special ("ferroresonant") transformer. Transformers are basically just big coils of wire wrapped around steel plates, and with standard 60-cycle-per-second AC current going through them, they can hum or buzz at a low (60 Hz) pitch if the wires loosen up a little with age.

There's not much that can be done to change this, short of replacing the converter. In your case, because the Magnetek 6345 was a very inefficient design to start with, you'd do well to put in a more modern converter such as a Progressive Dynamics Inteli-Power 9145 or 9160, and gain several advantages: much faster battery charging (meaning that when dry-camping, you won't have to run your generator nearly as long), less chance of overcharging your batteries when plugged into shore power, and so on.

"I also have what I believe to be a weak battery, because the other day, my generator wouldn't start."

It's possible that your house batteries are weak, but I'd suggest that the first thing to do is check their fluid levels. Batteries like yours need regular checking and topping off when necessary, and if the fluid level gets low, you won't get much power.

This is especially likely when plugged into shore power, as you are now. The 6345 converter is a crude device, and can easily overcharge your batteries and boil off much of their water if left plugged in for a long period.

Tip: if your house batteries don't have enough power to start your generator, try running the Ford engine for awhile; usually that will provide enough power (from its alternator) to get the generator going.

But in the long run, you need to make sure the house batteries are healthy... and it would help a lot if you replaced that old converter. :-)

Andy Baird

Travels with Andy
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Humming noise
Reply #2 –
Yahoo Message Number: 149386
Andy,

Pardon me for being pedantic, but a minor correction is needed.

60 Hz AC electric power produces a 120 Hz hum.  Instantaneously, there is a power peak at both positive and negative voltage peaks.  This is the effect seen in transformers.  In AC to DC converters, you're likely to have a "full wave" rectifier bridge which flips over the negative part of the sine wave doubling the number of positive sine wave parts.  This too gives primarily 120 Hz.

Wikipedia gets into this here:

https://en.wikipedia.org/wiki/Mains_hum

Alex Rutchka, SE #4 '05 MB
Re: Humming noise
Reply #3 –
Yahoo Message Number: 149387
Thanks Andy and Alex.

I'll look into the problem based on your suggestions.

Andy, just wanted to let you know your Skylark inspired me to RV in a Lazy Daze. Thank you again.
Re: Humming noise
Reply #4 –
Yahoo Message Number: 149388
"60 Hz AC electric power produces a 120 Hz hum."

I'm all for pedantry, Alex. :-) However, the Wikipedia article you cited appears to contradict what you said. It says, "The fundamental frequency of this sound is usually 50 Hz or 60 Hz, depending on the local power-line frequency." (For the US, it would be 60 Hz.) And the accompanying spectrum plot shows a strong peak at 60 Hz and relatively little amplitude at 120 Hz.

Andy Baird

Travels with Andy
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Humming noise
Reply #5 –
Yahoo Message Number: 149389
Doesn't really matter if it's 60 or 120 hertz, it's an annoying low  frequency hum or buzz from the ferro-resonant converter (which some folks refer  to as a "buzz box").
It will overcharge and boil the water out of your batteries and eventually  ruin them.  Go for one of the modern smart converters which, as someone  stated, will do a much better job of keeping your batteries charged and prolong  their life.
That old doorstop will make a good 12 volt bench power supply  for experimenter types.  If you don't know any of those folk, try  freecycle.

RonC

Humming noise

andybaird2000


  • Today at 8:49 PM

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      "60 Hz AC electric power produces a 120 Hz    hum."

      I'm all for pedantry, Alex. :-) However, the Wikipedia article you cited appears to contradict what    you said. It says, "The fundamental frequency of this sound is usually 50 Hz    or 60 Hz, depending on the local power-line frequency." (For the US, it would    be 60 Hz.) And the accompanying spectrum plot shows a strong peak at 60 Hz    and relatively little amplitude at 120 Hz.

      Andy    Baird

    Re: Humming noise
    Reply #6 –
    Yahoo Message Number: 149390
    I've got a hum too, and just assumed it was "normal". As I'm not comfortable doing this sort of thing, where's the best place to have this sort of work done?

    Pat
    The Pearl - 2000 31'
    "Of all the things I've lost, I miss my mind the most."
    Re: Humming noise
    Reply #7 –
    Yahoo Message Number: 149391
    Well, Andy it's all a question of what part of the linked article to look at.  Here is what I refer to:

    "Magnetostriction  is a second source of vibration, where the core iron changes shape  minutely when exposed to magnetic fields. The intensity of the fields,  and thus the "hum" intensity, is a function of the applied voltage.  Because the magnetic flux density is strongest twice every electrical  cycle, the fundamental "hum" frequency will be twice the electrical  frequency. Additional harmonics above 100 Hz or 120 Hz will be caused by  the non-linear behavior of most common magnetic materials."

    And further down:

    "This hum is usually at the second harmonic of the power line frequency (100 Hz or 120 Hz), since the heavy ground currents are from AC to DC converters that rectify the mains waveform."

    The "mains hum" is the effect between a constant magnetic field (i.e. the earth magnetic field or a permanent magnet in a speaker) and alternating magnetic field produced by the electric current in a wire.  That indeed would be 60 Hz in the US.

    But, we're getting far off the original topic.  Sorry about that.

    Alex Rutchka, SE #4 '05 MB
    Re: Humming noise
    Reply #8 –
    Yahoo Message Number: 149404
    I'm enjoying this thread. It has the potential to equal the famous "solar radiation through the driver's door window" topic of a few years ago. I wonder how many remember that one? Or am I really showing my age?

    WxToad
     Posted by: "Alex Rutchka"  rutchka Date: Sun Nov 9, 2014 5:07 am ((PST))

    Well, Andy it's all a question of what part of the linked article to look at.  Here is what I refer to: