What is this electronic component?
- Thread starter sams93
- Start date
Help Support UKworkshop.co.uk:
Sounds fine. The voltage rating of the replacement that you found also looks ok.
It was @Spectric 's point not mine, but placing the choke at that point in the circuit is about blocking electrical noise from the circuit board feeding back into the mains wiring. It will be needed for compliance with electromagnetic interference regulations.
StephenArfer
Established Member
I think you would end up chasing your tail trying to repair a board in this condition. It might even make your hair stand on end.
I'd suggest replacing the complete board. They are a common component in many types of equipment.
The form factor and connections might be different with any replacement, but you can usually deal with that quite easily. How about this? - Ebay Item
EMI = "Electro Magnetic Interference"
It's probably in the power circuit to prevent RF feedback from your dehumidifier back to the mains which might harm delicate electronics in the house. Ever switched something on which affects your workshop radio? Shouldn't happen nowadays but some no-name chargers and other illegally imported devices still cause it from time to time.
I'd suggest replacing the complete board. They are a common component in many types of equipment.
The form factor and connections might be different with any replacement, but you can usually deal with that quite easily. How about this? - Ebay Item
EMI = "Electro Magnetic Interference"
It's probably in the power circuit to prevent RF feedback from your dehumidifier back to the mains which might harm delicate electronics in the house. Ever switched something on which affects your workshop radio? Shouldn't happen nowadays but some no-name chargers and other illegally imported devices still cause it from time to time.
StephenArfer
Established Member
Please accept that I'm no expert on EMI, but I learnt what it was early on in my career as an aircraft (rotorcraft) maintenance engineer. HF radio and antenna installed - Transmit, and the emergency floats could inflate, or as I heard from other operations, Schermuly flares fired off. These flares were required "back in the old days" for a single-engine civil helicopter to be cleared for VFR at night in the UK. I installed the kit on a Bell 206A Jetranger. First power up with flares fitted was a bit sphincter tightening. Talk about lighting the blue touchpaper!
Both issues fixed by a modification to install a RF filter.
Both issues fixed by a modification to install a RF filter.
As others have suggested this is a Switched Mode Power Supply - SMPS and tbh likely cheaper to buy a replacement than attempt to repair. Also if the capacitor top you have damaged is the same value as the undamaged one on the right then it likely forms part of the input side mains rectified output smoothing and thus is 400V rated. If you have damaged the internals of it and you repair/replace what looks like a blown common-mode input choke filter then you quite likely will have fireworks as that capacitor blows up...
Better approach would be to find out if the voltage rating and hence current capabilities are - you state it's 40W so voltage x 40 = current, then look for a replacement on eBay - search open-frame SMPS
Better approach would be to find out if the voltage rating and hence current capabilities are - you state it's 40W so voltage x 40 = current, then look for a replacement on eBay - search open-frame SMPS
If that PCB board is in a bad condition with corrosion, what is the rest of the machine like ? Is it possible the corrosion has been caused by refrigerant leakage from the unit ?
Who is the manufacturer of this de humidifier ?
Who is the manufacturer of this de humidifier ?
It definitely looks like a common mode interference choke
That's it (different circuit diagram, but they are all pretty similar) on the left, marked EMI Coil Tranfo...
Although they are required for interference suppression legally speaking, many cheaper units don't even have one fitted!!! (including many OEM ones...)
In practice, any one rated for the current draw of the PSU would do the job, but it would be far easier to simply replace the entire unit with a new PSU (especially as you now have damage on the cap as well)
(they really aren't anything special- the only proviso is that they be able to carry the current used by the PSU safely- they don't have any particular properties other than that...)
How they work is that any interference generated internally in the PSU, will be transmitted back into the power lines- but because that interference will be 'equal but opposite' in phase each winding will generate a magnetic 'current' in the magnetic former, and being opposite, the interference will cancel each other out and be dissipated as heat in the former... (the incoming mains frequency, being in phase with each other, don't 'fight' in the magnetic former and pass through unhindered
a-guide-to-understanding-common-mode-chokes/
That's it (different circuit diagram, but they are all pretty similar) on the left, marked EMI Coil Tranfo...
Although they are required for interference suppression legally speaking, many cheaper units don't even have one fitted!!! (including many OEM ones...)
In practice, any one rated for the current draw of the PSU would do the job, but it would be far easier to simply replace the entire unit with a new PSU (especially as you now have damage on the cap as well)
(they really aren't anything special- the only proviso is that they be able to carry the current used by the PSU safely- they don't have any particular properties other than that...)
How they work is that any interference generated internally in the PSU, will be transmitted back into the power lines- but because that interference will be 'equal but opposite' in phase each winding will generate a magnetic 'current' in the magnetic former, and being opposite, the interference will cancel each other out and be dissipated as heat in the former... (the incoming mains frequency, being in phase with each other, don't 'fight' in the magnetic former and pass through unhindered
a-guide-to-understanding-common-mode-chokes/
Woody2Shoes
Impressive Member
I think that - as others have already said - this is a common-mode choke intended to reduce the amount of interference caused by the circuit, which would otherwise generate a lot.
Looking at the photo, I think that there as been a catastrophic event causing the winding to vaporize between the two points I've highlighted in red.
I think that the windings are flat because of the fact that these devices operate at frequencies where the 'skin effect' operates https://www.arrow.com/en/research-and-events/articles/the-skinny-on-the-skin-effect
At the sort of frequencies that these switching power supplies operate at, the skin depth in copper is only about 0.2mm.
If you look at the example diagram posted above, a broken winding will cut off power to the whole circuit. You have to ask yourself:
1) What caused this, and why didn't a fuse blow instead?
2) What other devices got damaged when this happened?
I'd be trying to draw a circuit diagram, by inspecting the board, and do some basic tests on the other components too. But I'd second/third/fourth? the suggestion that it would be safer and simpler to replace the whole module.
Looking at the photo, I think that there as been a catastrophic event causing the winding to vaporize between the two points I've highlighted in red.
I think that the windings are flat because of the fact that these devices operate at frequencies where the 'skin effect' operates https://www.arrow.com/en/research-and-events/articles/the-skinny-on-the-skin-effect
At the sort of frequencies that these switching power supplies operate at, the skin depth in copper is only about 0.2mm.
If you look at the example diagram posted above, a broken winding will cut off power to the whole circuit. You have to ask yourself:
1) What caused this, and why didn't a fuse blow instead?
2) What other devices got damaged when this happened?
I'd be trying to draw a circuit diagram, by inspecting the board, and do some basic tests on the other components too. But I'd second/third/fourth? the suggestion that it would be safer and simpler to replace the whole module.
Attachments
sams93
Established Member
I have to dissapoint you terribly by reporting that the reason the bits of copper are separated how they are is that I was prying with a screwdriver to see how bad the corrosion underneath had penetrated.
Nothing got damaged when it stopped working, I just went up to the shed one day and the lights on the machine was off. It had been running 24/7 for about 2 years at this point in a shed environment (although it's fairly insulated it's not the same as being indoors).
As you rightly say, replacement is more sensible, I just didn't like the idea of throwing something away if it was repairable, particularly as it had been working so well for so long.
Though the current that needs to pass through the coil is the 50Hz differential AC between L and N , the currents that the choke is intended to block are the high frequency common mode ones.
Woody2Shoes
Impressive Member
At this point, it really needs a new PCB entirely- the common mode filter is heavily corroded, and that damaged cap would need replacing as well, plus from your description there is still something else wrong as well to have made it stop working originally... (and its general overall shape looks to be in pretty poor condition... those aren't the only signs of corrosion visible on it)
I doubt a 'generic' supply would work, there's a LOT of plug/sockets on that PCB, which tends to suggest that it is a multi rail device (ie multiple voltages generated)- likely a 'specialty item' manufactured specifically for that unit
If you have a brand name/model number, I would suggest seeing if they have a repair section that could provide a new unit, otherwise you need to have someone who knows electronics and can test/trace the circuit and both 'clean it up, and repair it'...
IF a new one can be located, then I would strongly suggest a coating of 'spray on tropicalising protection' (often called 'conformal electronics coat' or similar, comes in 'brush on' and spray can versions) be applied to it before using it (we use it a lot here for protecting electronics- its basically a special insulating 'enamel' to prevent the kind of damage seen on that PCB from heat and moisture causing corrosion issues)
heat and moisture in a dehumidifier... lol
(although that type of application is precisely where you would expect to find both)
I doubt a 'generic' supply would work, there's a LOT of plug/sockets on that PCB, which tends to suggest that it is a multi rail device (ie multiple voltages generated)- likely a 'specialty item' manufactured specifically for that unit
If you have a brand name/model number, I would suggest seeing if they have a repair section that could provide a new unit, otherwise you need to have someone who knows electronics and can test/trace the circuit and both 'clean it up, and repair it'...
IF a new one can be located, then I would strongly suggest a coating of 'spray on tropicalising protection' (often called 'conformal electronics coat' or similar, comes in 'brush on' and spray can versions) be applied to it before using it (we use it a lot here for protecting electronics- its basically a special insulating 'enamel' to prevent the kind of damage seen on that PCB from heat and moisture causing corrosion issues)
heat and moisture in a dehumidifier... lol
(although that type of application is precisely where you would expect to find both)
