whats this component

[Thunderchild]

I have been given a SMPS and it has a funny lokking component in series with the AC supply (its right after the fuse) it consists of a central disk that looks like ferrite to me there is a washer tag on each side with the wires from it and plastic or ceramic spacers/washers on each end, the lot is bolted together. I can supply a pic if you don't know what it is off the bat.

Thanks
Simon

 

[Brian218]

Hi Simon,

A picture would be a big help; as they say, "a picture's worth a thousand words"

 

[crutschow]

It's likely an EMI (low-pass) filter to minimize contamination of the power line with SMPS switching noise.

 

[Blueteeth]

agreed, a large 'ferrite bead' type affair to attenuate high frequency components.

 

[Optikon]

It's likely an EMI (low-pass) filter to minimize contamination of the power line with SMPS switching noise.

Common mode.

 

[Thunderchild]

ok that sounds about it erm the ferite disk is partly broken is it going to be a problem ? if so could a suppressor be used i think there is a 2 X coil thing after it don't know if they have anyting to do with one another.

 

[mneary]

It's a NTC thermistor. Initially when the power is applied the resistance limits the inrush current. As the thermistor heats up a little, the resistance decreases and reduces the wasted power.

 

[Thunderchild]

hm so the fact that some of it is missing means that there is a little more resistance than there should be ?

 

[tonigau]

Looks like & easy fix, but begs the question why is is broke.
If its an open frame type supply then maybe just got knocked while laying around or could have been cracked during manufacture. Is there any evidence the broken disk has been hot.
Of all the SwitchMode supplies that I have repaired, 70% of parts I get from old boards & no comebacks. These used parts are "burned in" during use & are quite reliable generally. (except output electrolytics that are usually poor quality or overstressed)

So look around for an old TV or PC power supply of similar power Watts & you get your part for less than free.

 

[Thunderchild]

well as its an unboxed circuit board and it was given to me by someone that has had it lying around I guess its just had a bash and not been burnt out or anything the unit does appear to work although I havn't actually put a load on it yet