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Electronics => Beginners => Topic started by: HomeLate on March 06, 2021, 08:56:05 pm

Title: Identify part and how to check if it’s broken or not
Post by: HomeLate on March 06, 2021, 08:56:05 pm

Can this part be identified? And is it possible to check if it ok or not and if not, is it easy to find a replacement?

(https://i.imgur.com/mVIwnVZ.jpg)

(https://i.imgur.com/KqGeNe2.jpg)

Thanks!

Title: Re: Identify part and how to check if it’s broken or not
Post by: Terry Bites on March 06, 2021, 09:32:00 pm

Looks like a common mode choke, probably OEM. https://sme.co.uk/

Electrically its two coupled inductors AKA a transformer. Look for two isolated pairs of low ohms connections

Title: Re: Identify part and how to check if it’s broken or not
Post by: Algoma on March 07, 2021, 12:25:02 am

Its generally a noise filter for the AC mains, both incoming and outgoing. One half is connected to live, the other neutral. The wires simply in one pin, around the coil a few times and out the other pin. its a fairly simple construction.  It acts generally as noise filter for the AC line, by keeping the balance between live and neutral as they go through the coil.

Check that the wires on each half have an equal resistance.

Title: Re: Identify part and how to check if it’s broken or not
Post by: HomeLate on March 07, 2021, 07:05:28 am

Thank you both! I checked the resistance and it is 0.9 ohms on both ends. That looks fine to me so I have to continue my search.

This comes from a Compaq 1996 era psu which is non standard ATX/AT. The computer switches on as soon as I plug in the mains, while the power switch is switched off.

Title: Re: Identify part and how to check if it’s broken or not
Post by: SeanB on March 07, 2021, 09:17:31 am

If the power switch connects to the motherboard it is ATX, so power on type is set in the BIOS, to either power on with mains applied, stay off or to come on in last state. If the switch is connected to the power supply, and is fed mains voltage then it is an AT power supply, and the switch is faulty.

ATX power supplies always have a standby 5V supply there, even when the main power supply is turned off but mains is supplied. Thus the power on behaviour is controlled from the tiny embedded controller in the South bridge, which runs whenever standby power is applied, and which handles power sequencing, RTC alarm functions and, if enabled, will power up the network interface and listen in for a magic wake packet sent to the network card MAC address. That is why, if you have an old NE2000 or clone network card, you would have that 3 pin connector on card and motherboard for "Wake On LAN" support, that was invariably never used.