Bypassing a choke on the neutral

[adrianarcher]

Hi,

I have a wine fridge that doesn't work. I'm not 100% sure, but I think someone else may have tried to repair it unsuccessfully.

I have found a ET-24 choke that has a broken lead, and the repair won't be that easy. The PCB has a choke on both the line and neutral, it is the neutral one that is broken. I have included a picture of the choke, because I can't find a data sheet, the number is HEC2332/A ET-24, I think the manufacturer is GP

How bad is it if I just bypass this choke on the neutral? Am I right to think that this is for filtering noise feeding back into the grid?

Thanks,
Adrian

[Ian.M]

That's a common mode choke - the currents in the L and N coils are equal and opposite, and on the same core, so their inductance effectively cancels out, but common mode (on both L and N with the same phase) RFI is strongly attenuated.   If you bypass the N winding, its equivalent to adding an inductance in series with L. 

For testing, remove it completely and link across where it was.  If the fridge then works, try to either repair the choke or scavange a compatible replacement e.g. from a dead PC PSU or other appliance

[wasyoungonce]

Ian is totally correct. Usually the mrn on the choke may allow you to order a replacement but often it’s just the former type/ size etc. 

I’ve seen chokes & txfmrs break copper wire rugby near the PCB from mechanical stress or vibration.

Easy enough to take off unwind resolver break coat with insulating varnish & wind back on... oh take note of direction etc. 

Many of these common modes are very much alike as they are common items an thus very much alike in specs ... well for TVs etc

Brendan


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[Ian.M]

I think some of your meaning was obscured by the spell-chucker! e.g "... wire rugby near the PCB ..." and "... unwind resolver break ..." 

If you do remove a turn to get enough wire length to repair it, you need to do exactly the same to the other winding to keep it balanced.   If the broken wire end is on the outside of the winding or there's even 5mm left before it dives into the former, you'll probably be better off scraping and tinning the stub, then extending it by splicing on some magnet wire of similar thickness with its end pre-tinned,  sliding some 1mm bore heatsink over the joint for insulation and reconnecting it to the pin.  Don't pull it too tight, and apply a drop of rubbery impact adhesive where it runs round the edge of the former to damp the vibration that probably caused it to break.  Its a good idea to add a drop of adhesive to the other three wires.   DON'T use any adhesive that sets rock-hard.

[adrianarcher]

Thanks for all the suggestions everyone.

I was able to successfully repair the choke by soldering a pin onto the remaining wire and putting it back through the hole.

Unfortunately I’m pretty sure whoever tried to repair this in the past messed up two mosfets so badly by putting solder all over the traces effectively joining all their leads together. It’s not worth me trying to remove all this solder and fix them when if I wanted I could just buy a new board.