Mains noise filter - UK Vintage Radio Repair and Restoration Discussion Forum

Jolly 7 · 26th Sep 2019, 11:51 pm

Here is an unused filter purchased in Japan. It did not come with any instructions. Is this a mains filter that's supposed to remove mains-borne RF interference ? It has five terminals, two to the left and three to the right. If it is what I am thinking, how should it be connected to the mains ? Can someone please advise ?

Terry_VK5TM · 27th Sep 2019, 12:16 am

Before wiring it up, do a meter test to confirm there is a circuit between pin 1 and pin 3.
Same between pin 2 and pin 4.

Assuming that is OK (if not, tell us what you get):
Pin 3 incoming mains active
Pin 4 incoming mains neutral
Earth to central pin
Pin 1 active to circuit
Pin 2 neutral to circuit

You can actually change the incoming and outgoing around, I only suggested this configuration as it keeps the incoming earth line in proximity to the incoming mains active and neutral connections.

Jolly 7 · 27th Sep 2019, 1:15 am

Thanks Terry. Pins 1 and 3 are continuous, so are pins 2 and 4. My meter momentarily read 50 to 60 Megaohms between pins 1 and 2 and the same between 3 and 4 before jumping to OL. The earth pin is not continuous with any other pin. If all is OK, I might connect this to the regulated variable PSU I'm building at present.

Terry_VK5TM · 27th Sep 2019, 3:50 am

Sounds OK, the momentary 50 to 60 Megaohms is the bypass capacitors charging, so that's OK.

Are you going to use it on the incoming AC feed or somewhere else in your power supply?

Sideband · 27th Sep 2019, 6:36 am

Also do you have any idea what the maximum current capacity is?

Terry_VK5TM · 27th Sep 2019, 6:50 am

1A, it's written on the front.

Herald1360 · 27th Sep 2019, 10:52 am

Remember it'll only reduce conducted noise and then only if the earth at the point of use isn't as "dirty" as the line and neutral wires. A lot of mains borne interference actually gets picked up by radiation to the set in use, so the effect of the filter may be disappointing. Nothing to lose by trying it, though.

Jolly 7 · 27th Sep 2019, 7:52 pm

Quote:

Originally Posted by Terry_VK5TM

Sounds OK, the momentary 50 to 60 Megaohms is the bypass capacitors charging, so that's OK.

Are you going to use it on the incoming AC feed or somewhere else in your power supply?

I may have a problem with installing the filter because my PSU enclosure is part metal and I have earthed this directly to the mains plug. If I were to fit the filter inside the enclosure, then the earth wire would need to go to the filter input and I would lose the casing earth connection. Is there a solution to this ?
The other issue is that the filter has pins that need to be soldered to a PCB and if I do that the PCB will have live mains voltage. Not sure how to insulate the PCB properly to make it acceptably safe and shock free. Any suggestions please ?

Jolly 7 · 27th Sep 2019, 8:05 pm

Picture attached. The yellow wire is earth connected to the metal base of the enclosure.

Refugee · 27th Sep 2019, 10:05 pm

I would just crimp a ring tag onto a short bit of green and yellow wire and add it to the earth post on the case and solder the other end to the filter earth.

Herald1360 · 27th Sep 2019, 10:39 pm

If the filter has only pins and no other mounting arrangement then easiest way to use it would be to mount it on some 1.6mm ERBGF (fibreglass PCB material, bare- no copper) sheet with the pins pushed tightly through suitable holes. Soldered wire connections can then be made direct to the pins and the whole assembly mounted to the equipment using further holes in the ERBGF sheet and suitable nuts, bolts and spacers.

For the box you show, it could be mounted on its insulating plate on the outside of the box with suitable clearance holes in the box around each connection so that all wiring is inside the box.

Terry_VK5TM · 28th Sep 2019, 1:36 am

As per Herald, but I would mount the filter inside the box if you have the room.

If you make the standoff's fractionally shorter than the height of the filter, it will clamp it to the back of the case.

Jolly 7 · 29th Sep 2019, 1:24 am

Quote:

Originally Posted by Refugee

I would just crimp a ring tag onto a short bit of green and yellow wire and add it to the earth post on the case and solder the other end to the filter earth.

Thank you very much. This has been successfully implemented.

Jolly 7 · 29th Sep 2019, 2:26 am

And here is the filter mounted on thick insulating plastic material as I had no copperless board. The plastic in turn is screwed down to wooden blocks affixed to the base of the metal enclosure.

Herald1360 · 29th Sep 2019, 4:50 pm

Other than the very slight extra fire hazard in the event of other problems from the use of wood and unknown plastic material (PCB ERBGF is usually rated for UL94-V-0 fire resistance) that should be just fine.

ColinTheAmpMan1 · 30th Sep 2019, 12:32 pm

Quote:

Originally Posted by Refugee

I would just crimp a ring tag onto a short bit of green and yellow wire and add it to the earth post on the case and solder the other end to the filter earth.

OK, so I'm being a bit "H&S" here

, but it would actually be better to make a separate connection to the metal casing. That way, it would meet current standards for safety earth better, even if you don't use the multitude of nuts, locknuts and lockwashers that are specified for the connection of the safety (mains) earth.

Colin.

Refugee · 30th Sep 2019, 2:45 pm

Yes I agree you need a star washer between each layer of the termination.

26th Sep 2019, 11:51 pm	#1
Jolly 7 Octode Join Date: Feb 2018 Location: Southampton, Hampshire, UK. Posts: 1,063	Mains noise filter Here is an unused filter purchased in Japan. It did not come with any instructions. Is this a mains filter that's supposed to remove mains-borne RF interference ? It has five terminals, two to the left and three to the right. If it is what I am thinking, how should it be connected to the mains ? Can someone please advise ? Attached Thumbnails

27th Sep 2019, 12:16 am	#2
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: Mains noise filter Before wiring it up, do a meter test to confirm there is a circuit between pin 1 and pin 3. Same between pin 2 and pin 4. Assuming that is OK (if not, tell us what you get): Pin 3 incoming mains active Pin 4 incoming mains neutral Earth to central pin Pin 1 active to circuit Pin 2 neutral to circuit You can actually change the incoming and outgoing around, I only suggested this configuration as it keeps the incoming earth line in proximity to the incoming mains active and neutral connections. __________________ Terry VK5TM https://www.vk5tm.com/

27th Sep 2019, 1:15 am	#3
Jolly 7 Octode Join Date: Feb 2018 Location: Southampton, Hampshire, UK. Posts: 1,063	Re: Mains noise filter Thanks Terry. Pins 1 and 3 are continuous, so are pins 2 and 4. My meter momentarily read 50 to 60 Megaohms between pins 1 and 2 and the same between 3 and 4 before jumping to OL. The earth pin is not continuous with any other pin. If all is OK, I might connect this to the regulated variable PSU I'm building at present.

27th Sep 2019, 3:50 am	#4
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: Mains noise filter Sounds OK, the momentary 50 to 60 Megaohms is the bypass capacitors charging, so that's OK. Are you going to use it on the incoming AC feed or somewhere else in your power supply? __________________ Terry VK5TM https://www.vk5tm.com/

27th Sep 2019, 6:36 am	#5
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,577	Re: Mains noise filter Also do you have any idea what the maximum current capacity is? __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

27th Sep 2019, 6:50 am	#6
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: Mains noise filter 1A, it's written on the front. __________________ Terry VK5TM https://www.vk5tm.com/

27th Sep 2019, 10:52 am	#7
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Mains noise filter Remember it'll only reduce conducted noise and then only if the earth at the point of use isn't as "dirty" as the line and neutral wires. A lot of mains borne interference actually gets picked up by radiation to the set in use, so the effect of the filter may be disappointing. Nothing to lose by trying it, though. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

27th Sep 2019, 8:05 pm	#9
Jolly 7 Octode Join Date: Feb 2018 Location: Southampton, Hampshire, UK. Posts: 1,063	Re: Mains noise filter Picture attached. The yellow wire is earth connected to the metal base of the enclosure. Attached Thumbnails

27th Sep 2019, 10:05 pm	#10
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Mains noise filter I would just crimp a ring tag onto a short bit of green and yellow wire and add it to the earth post on the case and solder the other end to the filter earth.

27th Sep 2019, 10:39 pm	#11
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Mains noise filter If the filter has only pins and no other mounting arrangement then easiest way to use it would be to mount it on some 1.6mm ERBGF (fibreglass PCB material, bare- no copper) sheet with the pins pushed tightly through suitable holes. Soldered wire connections can then be made direct to the pins and the whole assembly mounted to the equipment using further holes in the ERBGF sheet and suitable nuts, bolts and spacers. For the box you show, it could be mounted on its insulating plate on the outside of the box with suitable clearance holes in the box around each connection so that all wiring is inside the box. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

28th Sep 2019, 1:36 am	#12
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: Mains noise filter As per Herald, but I would mount the filter inside the box if you have the room. If you make the standoff's fractionally shorter than the height of the filter, it will clamp it to the back of the case. Attached Thumbnails __________________ Terry VK5TM https://www.vk5tm.com/

29th Sep 2019, 2:26 am	#14
Jolly 7 Octode Join Date: Feb 2018 Location: Southampton, Hampshire, UK. Posts: 1,063	Re: Mains noise filter And here is the filter mounted on thick insulating plastic material as I had no copperless board. The plastic in turn is screwed down to wooden blocks affixed to the base of the metal enclosure. Attached Thumbnails

29th Sep 2019, 4:50 pm	#15
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Mains noise filter Other than the very slight extra fire hazard in the event of other problems from the use of wood and unknown plastic material (PCB ERBGF is usually rated for UL94-V-0 fire resistance) that should be just fine. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

30th Sep 2019, 2:45 pm	#17
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Mains noise filter Yes I agree you need a star washer between each layer of the termination.