Help,transformers buzzing

[Electric flower]

In past two days weird stuff started happening.
For some reason i can't figure out why transformers are buzzing on my equipment.
For roughly one month everything worked fine untill two days ago.
As soon as i heard it i turned them off. I tried powering them some time after and same happened.

My own DIY PSU started buzzing yesterday and i tought it was due to my failure or just cheap components.
Weller PU 81 soldering station (base) today when i turned it on also started buzzing and i even heard some poping.

I live in Croatia in town that has very unstable mains, they go from 190V to 245V. (230V is what they are supposed to be)
I also tought of condensation but last few days were warm and sunny, and for some other reasons i think this is not likely the case, also there has been no spilling on the desk.

I have opened both cases and everything looks fine, no carbon anywhere.

Please help becouse im scared shitlessly, stuff i saved money for almost half a year is trying to kill me or at least make me insane.

Also to note, insides of both cases and boards smell like some sort of candy, they didn't smell like this before. No fuses were blown.

Weller PU81 uses 0.5A Time.
My psu uses 1.5 A time.

Thanks for help and sorry for poor English.

[mariush]

The power supplies that use those classic large and heavy transformers are more sensitive to the input voltage. Those transformers output a voltage that's a percentage of the input voltage ( for example  230v in, 24v out makes it 9.5 : 1  , so if you have 195v at the socket, the transformer may output only 20v  and that could hurt the device.

The soldering station... will probably be fine, most of the energy is used by the heating element, and lower voltage just means it will heat up slower.
Your DIY power supply... well, I guess it depends on your design.

Your problem may be related to the mains frequency.. due to the flooding or whatever happens in your country, the power grid may be affected and the mains frequency may move around, won't be a stable 50 Hz. Some classic transformers will make noise when they get such mains frequencies combined with irregular input voltages.


Computers, monitors etc use switching power supplies, which work differently, rectifying ac voltage to dc (up to 400-420v) and then convert it to lower voltages, so they're not so sensitive to mains voltage or frequency.

[retrolefty]

I too think that frequency variation is most likely responsible for your buzzing transformers. Not much you can do about it short of just not using the effected equipment.

[Electric flower]

I'm not in part affected by floods but that does not exclude possobility of frequency variations.

But what with candy smell? Could that be due to heating or something being done to insulation varnish on coils?

[Richard Crowley]

I live in [wherever, actually] that has very unstable mains,...

If I  lived in a place with unstable power mains, and especially if I had much electronic gear powered from those unstable mains I would get (or MAKE) a power monitor that would at least show the voltage and frequency.  And with a cheap Arduino (or equivalent) you could make a cheap monitoring device that could log voltage and/or frequency excursions and time-stamp them.

Maybe a logging power mains monitoring gadget is an interesting DIY project.

[Jeroen3]

My soldering iron/hot-air also has a buzzing transformer. Its buzzing at 50 Hz while "off" and about 1 sec with the iron on (probably the heater control instability).
I'm not putting any effort in it since cheap non-potted transformers do this. Even the big kV one's. Or those small switching regulator ones, just on a higher frequency.

That candy smell might just be the smell of all the electronics in there, nothing to worry about.
Unless you have some weird candy over there that smell like burned electronics.

@Richard, those projects are also (more) dangerous on (unstable) mains. Get some proper safety components.

[Paul Price]

A candy smell is a clear sign that a transformer has been overloaded or overheated and might soon issue forth smoke.

[Paul Price]

 The buzzing can be silenced by applying a few drops of superglue to the lamination.

[c4757p]

A candy smell is a clear sign that a transformer has been overloaded or overheated and might soon issue forth smoke.

That's what the wire enamel smells like when it melts. Watch out with this one.

[IanB]

The best, but very expensive, option is to get a power conditioning UPS with a clean and regulated output voltage. The slight snag here, apart from the cost, is that the bad mains might fry the input side of the UPS.

However, it's hard to avoid the sense that if the mains is bad, it's not a good idea to plug stuff into it.

[johansen]

unless there is some natural resonance, most all transformer buzzing is going to be caused by high line voltage, or low line frequency. increasing frequency or reducing line voltage (or both), reduces flux and the electrostriction effect, which reduces noise.

[planet12]

One possibility that hasn't been mentioned is a DC bias on the mains.

This will both dissipate power directly through I²R losses in the windings, and also will have the effect of magnetically basing the core - and the AC mains on top of that could be causing the core to reach saturation - causing a precipitous drop in magnetising inductance, and hence increase the current drawn through the primary winding.

To summarise, one or more of these will be causing you grief:

• DC bias - I²R losses
• DC bias moving core towards saturation
• AC voltage too high - exceeding volt-seconds core can handle
• AC frequency too low - exceeding volt-seconds core can handle

[Shredhead]

Yeah, I made a regulated power supply recently and you could feel the transformer vibrating.  At first I was concerned but it's been on for about a year straight now and nothing bad has happened.  I think the transformer I got is not of the best quality and they didn't glue the core plates very well so the main's frequency vibrates them.  I have also noticed that cheap switching supplies make a high pitched "whine" when you go up to them closely.

Now "poping" is a different story.  That kind of worries me.  The only thing I've been around that pops are electro caps when they blow from too much voltage.  Maybe that is the problem?  Too high of a mains voltage which is heating up your transformer to the point of breaking down the glue (candy smell) making them vibrate and blowing the filter caps?  Sorry about your power stations where you live, that would be hard to deal with.

"Scared shitlessly"  That's a good one dude, I'm going to say that all the time now!  Power supplies will do that to ya.  I was working on one while playing one of Dave's EEVblog videos on youtube in the background and you know how at the end of his videos it makes that "ZOOURRRCH" electrical zap noise?  I shit my pants. 

[rexxar]

Weller PU 81 soldering station (base) today when i turned it on also started buzzing and i even heard some poping.

Do you mean capacitor rupture popping, or electrical ark "snapping"?

A sharp snap or popping sound with the candy smell of melting enamel would suggest arcing in your transformers, especially if you don't see any other damaged components.

[VK5RC]

I recently moved house and was pleased to see the mains switchboard had an earth leakeage detector but it also included under AND overvoltage cut out.  It looks like a wholesale electrical fitting,  if you can find one easily it may be a good investment.

[Richard Crowley]

@Richard, those projects are also (more) dangerous on (unstable) mains. Get some proper safety components.

No issue with using proper safety components.

But a properly designed DIY monitor can use a safe wall wart to isolate the monitor from the mains while retaining the ability to monitor mains voltage and frequency. Even operating on "battery backup" in the case of extremes of mains voltage (up or down).

The informed way of selecting the "proper safety components" often requires some idea of what is happening on your mains feed.  And commercial power monitors are typically way out of the reasonable budget for hobby or home users.  But we now have the technology do do the basic monitoring (voltage and frequency, and even current where necessary) quite inexpensively.  There are commercial products like "Kill-A-Watt" that will do basic measurement. And I think they even to simplistic tracking (keeping track of MIN and MAX (?)  And there are wireless hacks to them so you can send data to your Arduino, etc.

In fact, it appears that there are some projects to do just that already underway...
http://dangerousprototypes.com/2012/11/09/loggrid-power-line-frequency-and-voltage-monitorlogger/
http://www.edcheung.com/automa/power.htm

[Electric flower]

After some time i had free morning (mains less used and more stable) and i tested it all, they both work fine.
Poping i heard yesterday it was like 2-3 pops per second but they werent loud as 230V arcing

Thanks for the help and here are some photos of Weller

[Electric flower]

White blocks are here becouse i had to reduce picture size or else i would not be able to upload it