What is a good Earth for radios use. - UK Vintage Radio Repair and Restoration Discussion Forum

ChristianFletcher · 29th Jul 2004, 6:31 pm

I have a question about earthing my GEC BC5645, but I am sure this question is common to many other sets.

I had a problem with mains hum that could be heard on some very quiet sections of music when played at high volume. While trying to track down the hum I used my scope and found that earthing out the chassis with the probe return cured the problem. The radio's mains lead it only two core with no provision for an earth. However the chassis does have provision for an earth via a plug on the back. This earth is a solid connection not through a capacitors such as used on floating chassis.

Where is the correct source for earth on valve radio's , did the previous users in the past go and bang and copper stake into the garden and why did they not earth the chassis through the mains lead - perhaps to prevent earth loops ?

Regards Chris

ajgriff · 29th Jul 2004, 6:37 pm

Hi Chris

I think the primary reason for not earthing via the mains was that the old round pin sockets very often had only two pins ie, no provision for earth.

Cheers.

Alan

Sam · 29th Jul 2004, 7:01 pm

I agree. When the radios were mew there were not earth pins in sockets. Some people ran them from adaptors in light-fittings

. I always replace the original 2-core leads with 3-core leads, if possible. You cannot earth AC/DC sets, or autotransformer ones. AC-only sets with 'proper' primary/secondary transformers can, and should, be earthed. As has been said before, safety comes before originality!

Sam

ChristianFletcher · 29th Jul 2004, 7:12 pm

Thanks for that info.

I do earth this types of chassis as a matter of course. I have not come across any mains plugs without an earth - apart from those isolated shaving plugs. How many types of plugs were around in the past ?

I remember seeing those 5 amp plugs without fuses and those three pin plugs that have a round pin right in the middle.

Chris..

AC/HL · 29th Jul 2004, 7:36 pm

In the early days most houses, if wired for mains at all, only had lighting circuits. This is why early radio books often show adaptors in light sockets. Even when power was introduced (5 & 15 amp unfused round pin sockets) there was often only one socket upstairs & one downstairs, often on the cooker box.

29th Jul 2004, 6:31 pm	#1
ChristianFletcher Heptode Join Date: Dec 2003 Location: South Yorkshire, UK. Posts: 900	What is a good Earth for radios use. I have a question about earthing my GEC BC5645, but I am sure this question is common to many other sets. I had a problem with mains hum that could be heard on some very quiet sections of music when played at high volume. While trying to track down the hum I used my scope and found that earthing out the chassis with the probe return cured the problem. The radio's mains lead it only two core with no provision for an earth. However the chassis does have provision for an earth via a plug on the back. This earth is a solid connection not through a capacitors such as used on floating chassis. Where is the correct source for earth on valve radio's , did the previous users in the past go and bang and copper stake into the garden and why did they not earth the chassis through the mains lead - perhaps to prevent earth loops ? Regards Chris __________________ Every Silver Lining Has Its Cloud https://youtube.com/channel/UCvBpiuUUnErJlNBm6DWb3Ww

29th Jul 2004, 6:37 pm	#2
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: What is a good Earth for radios use. Hi Chris I think the primary reason for not earthing via the mains was that the old round pin sockets very often had only two pins ie, no provision for earth. Cheers. Alan

29th Jul 2004, 7:01 pm	#3
Sam Hexode Join Date: Apr 2003 Location: Higham-on-the-Hill, Leicestershire, UK. Posts: 338	Re: What is a good Earth for radios use. I agree. When the radios were mew there were not earth pins in sockets. Some people ran them from adaptors in light-fittings . I always replace the original 2-core leads with 3-core leads, if possible. You cannot earth AC/DC sets, or autotransformer ones. AC-only sets with 'proper' primary/secondary transformers can, and should, be earthed. As has been said before, safety comes before originality! Sam __________________ Can he lead a Normal life, Doctor? No, he will be ... an Engineer.

29th Jul 2004, 7:12 pm	#4
ChristianFletcher Heptode Join Date: Dec 2003 Location: South Yorkshire, UK. Posts: 900	Re: What is a good Earth for radios use. Thanks for that info. I do earth this types of chassis as a matter of course. I have not come across any mains plugs without an earth - apart from those isolated shaving plugs. How many types of plugs were around in the past ? I remember seeing those 5 amp plugs without fuses and those three pin plugs that have a round pin right in the middle. Chris.. __________________ Every Silver Lining Has Its Cloud https://youtube.com/channel/UCvBpiuUUnErJlNBm6DWb3Ww

29th Jul 2004, 7:36 pm	#5
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: What is a good Earth for radios use. In the early days most houses, if wired for mains at all, only had lighting circuits. This is why early radio books often show adaptors in light sockets. Even when power was introduced (5 & 15 amp unfused round pin sockets) there was often only one socket upstairs & one downstairs, often on the cooker box.