Power supply QRM shielding - UK Vintage Radio Repair and Restoration Discussion Forum

Malcolm T · 29th Apr 2020, 2:10 pm

I have a very nasty qrm coming from my psu inside the computer . Does anyone have any suggestions as to how to tackle this please . I have not had it apart yet so dont know if there are some critical filtering components missing !.

Thank you.

29th Apr 2020, 4:41 pm

I think you are right about missing filter components, all too prevalent today. A portable radio waved around the mains cable will find out.

Andrew2 · 29th Apr 2020, 5:22 pm

I found our previous PC was putting a lot of noise onto the mains lead and it was radiating all over the house.
So I made a short flylead which plugged into the PC's IEC socket and was fitted with a filtered IEC socket, see picture. This socket was mounted in a small plastic box for safety. Once fitted, peace & quiet reigned again!
The filtered socket came from Surplectronics. https://www.surplectronics.com/ It's listed under capacitors.

Malcolm T · 29th Apr 2020, 6:14 pm

Thanks for replies. Looks like i,m going to have the lid off and take a look see first then maybe even roll my own filter , its very noisy its unreal on the s meter.

Radio Wrangler · 29th Apr 2020, 6:39 pm

You'll probably find a nice virgin area on the PCB ready for X and Y capacitors, and a pair of links where a common mode choke ought to have been. Probably was on the one sent for testing. Fitting these ought to be a start. Adding a big ferrite on the output wires might help as well. 1 per connector.

David

Malcolm T · 29th Apr 2020, 8:39 pm

Yep, that's got me curious now as to missing stuff!!!. We shall see.

29th Apr 2020, 2:10 pm	#1
Malcolm T Hexode Join Date: Dec 2018 Location: Lugo, Spain Posts: 265	Power supply QRM shielding I have a very nasty qrm coming from my psu inside the computer . Does anyone have any suggestions as to how to tackle this please . I have not had it apart yet so dont know if there are some critical filtering components missing !. Thank you.

29th Apr 2020, 4:41 pm	#2
Guest Guest Posts: n/a	Re: Power supply QRM shielding I think you are right about missing filter components, all too prevalent today. A portable radio waved around the mains cable will find out.

29th Apr 2020, 5:22 pm	#3
Andrew2 Octode Join Date: Mar 2010 Location: Dukinfield, Cheshire, UK. Posts: 1,945	Re: Power supply QRM shielding I found our previous PC was putting a lot of noise onto the mains lead and it was radiating all over the house. So I made a short flylead which plugged into the PC's IEC socket and was fitted with a filtered IEC socket, see picture. This socket was mounted in a small plastic box for safety. Once fitted, peace & quiet reigned again! The filtered socket came from Surplectronics. https://www.surplectronics.com/ It's listed under capacitors. Attached Thumbnails __________________ Andy G1HBE.

29th Apr 2020, 6:14 pm	#4
Malcolm T Hexode Join Date: Dec 2018 Location: Lugo, Spain Posts: 265	Re: Power supply QRM shielding Thanks for replies. Looks like i,m going to have the lid off and take a look see first then maybe even roll my own filter , its very noisy its unreal on the s meter.

29th Apr 2020, 6:39 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 19,761	Re: Power supply QRM shielding You'll probably find a nice virgin area on the PCB ready for X and Y capacitors, and a pair of links where a common mode choke ought to have been. Probably was on the one sent for testing. Fitting these ought to be a start. Adding a big ferrite on the output wires might help as well. 1 per connector. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

29th Apr 2020, 8:39 pm	#6
Malcolm T Hexode Join Date: Dec 2018 Location: Lugo, Spain Posts: 265	Re: Power supply QRM shielding Yep, that's got me curious now as to missing stuff!!!. We shall see.