# my bed humms



## johng1974 (Jan 17, 2007)

well, the electrickery underneath it does.. 

I have moved back to the rear bedroom for a while..
And the noise is getting to be a pain... I am happy to unplug the hookup overnight, but the fridge will loose (a little) cold..

is this humming most likely to be the yellow step down transformer, or the van's charging / electricity unit, do you think?

I will take a proper look as soon as i can,,

thanks as always 
John

oh.. and when a 240V fan heater came on last night, the humming subsided for the time the fan was on..


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## 98452 (Apr 2, 2006)

My charger hums to but located under the fridge.

Interestingly enough was quiet while using it in the States.


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## zaskar (Jun 6, 2005)

johng1974 said:


> ge will loose (a little) cold..
> 
> is this humming most likely to be the yellow step down transformer, or the van's charging / electricity unit, do you think?
> 
> oh.. and when a 240V fan heater came on last night, the humming subsided for the time the fan was on..


It's a bit of both, ours does the same, some are worse than others and there's basically beggar all you can do about it unless you want to spend a LOT of money on isolation mounts and accoustic blanketing to line the locker in which the unit is situated. It because of the differences in American/UK frquencies (240V at 50HERTZ versus 110 at 60 HERTZ (or is it the other way round, i alwways flippin forget this one!


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## johng1974 (Jan 17, 2007)

thanks RR..

on that subject, why are RV fridges so quiet!? they presumably have a different cooling system than domestic ones?

The grey powerunit in my van... what is its purpose.. it must send 12V to the batterie(s), does it receive 110 from yellow and then send this out to all 110 sockets, appliances?

so, 240V comes in (to Fusebox (cant remember its proper name, domestic unit?)

then
goes to yellow and also to 240V sockets, and then from yellow to grey as 110v - am i sort of right?

J


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## johng1974 (Jan 17, 2007)

Thanks Zas...

I have a load of acoustic carpet stuff.... well a few meters...

hmm


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## zaskar (Jun 6, 2005)

johng1974 said:


> Thanks Zas...
> I have a load of acoustic carpet stuff.... well a few meters...
> hmm


Just be carefull not to "stiffle" the unit. they create a surprising amount of heat, especilly if it's a hot day and the aircon is going sub-orbital!
The locker door for ours has a small "judas" gate in it, a small 4" square door which can be opened to allow excess heat out. Im seriously toying with fitting a small extractor fan on a thermostat cos as i say, the heat build up in the locker is quite surprising.


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## 98064 (Mar 10, 2006)

Yellow transformer sound suspiciosly (never could spell that word!) like a building site job to me, is it? Can't remember the full argument but I seem to remember there are issues using them for RV's.
Anyway, our transformed humms like the proverbial, I just un plug if it bothers us, getting used to it now though.
Apparently you can get silent ones £££££££'s.

Si


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## johng1974 (Jan 17, 2007)

I have a PC in one cupboard

(drives TV Music Net etc) 

the heat from that is unbelievable!!

need an extraction fan for that one


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## johng1974 (Jan 17, 2007)

yes building site job 

remember reading on here about them not being on all the time so think I will start unplugging overnight 

suspiciously i thik

oops

think

I am sure my spelling has got a lot worse since i left school... crossword time I guess..


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## Scotjimland (May 23, 2005)

Hi John

Mine is a 'building site' tranny.. rated at 3kva and it does get hot, but it's been in use for 10 years with no problem, and yes it does hum ..

If you want change, fit one of these .. £75 for a 3kva

>>Air link transformers<<

Don't be tempted to fit larger than you need, the larger the transformer is the more likely it is to trip site supplies when you first switch on due to high inrush currents.


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## johng1974 (Jan 17, 2007)

thanks J will have a look


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## Snelly (Aug 20, 2005)

I have a yellow transformer jobbie too. Mine doesn't humm, but the charging system for the batteries does. It has a fan which humms and whirrs! :lol:

Its not much of a problem though, because we havent been on hook up in ages, damn rallys! :lol:


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## 99181 (May 12, 2006)

hi...under our cooker humms and at night the magic wizard flashes no probs though it's just the fan on the charger...lol


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## olley (May 1, 2005)

Hi 110v building site trannys are 2 phase and deliver 55volts on both conductors 180 degrees out of phase. 

Because of this they can't be used in reverse (110-230) unlike normal transformers. So if you want 230 from your genny you need another tranny. And thats the only real drawback.

Olley


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## johng1974 (Jan 17, 2007)

ooh..

i haven't tried the genny yet, but your saying when I do, it will most likely power all 110V and 12V i.e. fridge/lights/charging/AC and that's it..

no 240 Volt stuff at all?


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## olley (May 1, 2005)

Hi no not unless you have a 110-230 tranny. Most of the professional conversions I have seen use a single tranny to supply 110v on hook up and are reverse fed when you run the genny to give 240v.

Olley

No offence meant with the word "professional" guys


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## gromett (May 9, 2005)

Humm from electical device is mains hum and is usually always the transformer.

When a transformer is made the wire is wrapped around a plastic (or similar) core. This is then laminated with thin metal sheets shaped like the Letter I and the letter E which are put in alternately. ie
first an E is put in from one side of the coil then one from the other side.
The i's are then slid in the gaps after the full stack of E's has been applied.

Piccy here http://www.ec21.com/company/k/kscmotor/upimg/tra_2.jpg

The whole transformer is then varnished to solidify and seal the block of metal. This serves two purposes one is to get rid of air gaps which cause eddie currents in the magnetic field but the other is to lock the laminations in place to prevent them vibration in the 50Hz magnetic field.

If the laminations are not packed tight enough or they are not left in the varnish tank long enough the laminations will vibrate and cause that annoying hum.

This cannot be fixed easily without replacing the transformer, But if you are comfortable with electrics you can try applying a thin coat of araldite or other epoxy resin around the core of the transformer. This sometimes works as it deadens the vibrations. Please note if you attempt this it is at your own risk and voided waranties and risk of electric shock may result. Please be careful not to put too much on as it may cause overheating it really is just a thin layer to lock the laminations in place.

This is one of the reasons I like the Victron Inverters is that it uses a toroidal transformer that doesn't suffer this problem (although the fan can be loud under full load in hotter climes)

Cheers
Karl


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## johng1974 (Jan 17, 2007)

thanks Olley


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## johng1974 (Jan 17, 2007)

cheers Karl too
I will live with it a while longer.. enough has broken in two months already


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## 99702 (Jun 18, 2006)

the only thing that hums in ours is the on board charger, clicks in and out very annoying so i flick the breaker only runs that ,of at night and let the van run on its batts only the fridge and a light, i thought it was the tranny but its silent, worth checking


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## gromett (May 9, 2005)

peabug said:


> the only thing that hums in ours is the on board charger, clicks in and out very annoying so i flick the breaker only runs that ,of at night and let the van run on its batts only the fridge and a light, i thought it was the tranny but its silent, worth checking


The charger has a transformer in it as well :wink:

Karl


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## LC1962 (Oct 6, 2005)

You will find that the newer digital charge convertors are a lot quieter than the old style linear ones.


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## gromett (May 9, 2005)

They are indeed quieter but they still have a transformer which is a lot lighter weight and operates as a switched mode. Problem with these tends to be a whine rather than a hum as the frequency the transformer uses is higher and the volume changes depending on load. Sounds a lot like the sound you used to get from the back of a telly (EHT Tranny).



These switched mode chargers annoy youngesters a lot more as the harmonics of the higher frequencies tend to fall on deaf ears once you reach 25 or so :lol: 

Karl


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## johng1974 (Jan 17, 2007)

well i am sick of this office....

home for whatever I can drink then ;later off to bed for zz's I''ss and e'ss 


J


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## G2EWS (May 1, 2006)

Linda beat me to it!

You may recall when I bought the Winnie I had a problem with my charger under the fridge/freezer. This unit went kaput which as mentioned was caused by the change in frequency between US and UK.

Here is a clip out of my thread of 26/6/06:


(Thursday, just getting ready to leave for the office and check in the MH. The batteries have discharged to about 9V! Oh dear! Again a quick check (all suited up ready for work) and it appears there is nothing coming out of the 110V to DC converter and charger. Quick search on the internet for the Magnetek 6345 converter finds information including circuit diagrams and a fault flow chart. Which confirms the unit is not only duff, but not a good one either.

Mmm, decide to call Stateside Tuning and chat with Linda and James. Brilliant, James does not even have to think about it. 'Your RV is what year?' 'Oh well you will have the Parallex 6300 series, it will only last a few days with 50hz I guess it is broken' 'Correct' I say, 'can you help I have a Wife and Daughter who will lynch me if am not ready for the weekend - gulp'. 'It just so happens that I have a new model in stock' says James. 'I'm on my way'. Off to Moreton In The Marsh to visit the very helpful Linda as James had to go out. Return and install the power unit and hey presto we have 12V and guess what? No noise, zilch, silence! Ahh.)


Seems to me changing the charger is probably a low cost way of getting peace and quiet. Wish I could get rid of snoring as quickly!!

Regards

Chris


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