AR88D Earthing ( or lack of )? - UK Vintage Radio Repair and Restoration Discussion Forum

Aub · 9th Oct 2012, 9:27 am

Hello All,

My AR88D receiver has, what looks like, the original mains power lead. The mains lead has connections to live and neutral, in the 13A plug, both coloured black and has a black rubber outer. There is no earth connection.

When the receiver is connected to my transmitter, it gets a mains earth via the mains earth on the transmitter, but if I use it on its own it doesn't get a mains earth. I've thought of fitting a 3 core mains lead, for safety reasons, but wondered if there is a down side to doing this?

Thanks.

Aub G4KQL

Radio Wrangler · 9th Oct 2012, 10:00 am

The AR88 mains side is not to the standard for floating operation and the receiver must be earthed. Relying on other things is always a bit dodgy and having things which require unobvious precautions is risky too. Say I come off my horse this evening and break my neck (I'll try not to). My house will need clearing and there are two AR88s there. Both with 13A plugs on them. Someone is going to try them in the most obvious way, plug one in and see what happens. I don't want to leave anything in an unobvious dangerous condition.

The older of my two was rebuilt in 1953 (according to the RAF label stuck to the outside of the right side gusset plate) with a PVC wiring harness, and they replaced the mains cable. PVC, red, black and green cores.

The younger AR88 has not been rebuilt and has the original wiring, though someone has replaces the mains lead. The internal stuff is crumbly. I wouldn't trust it without a solid earth and an RCD.

I don't think a 2-wire mains cable is original for an AR88 shipped to the UK, anyway

David

Breaking earths is usually done for breaking up audio hum loops, or for very dodgy floating of oscilloscopes.

G6Tanuki · 9th Oct 2012, 12:14 pm

You really should use a proper 3-core cable and a proper earth.

When I bought my AR88D back in the late-1970s (from a place that used to advertise in the back of "Wireless World" - I forget their name but their ads were always in a narrow column down the full length of the page) it came in an ex-UK-military wooden transit-case with Air Ministry markings and a fairly thick 3-core PVC mains lead - paradoxically colour-coded red, white and yellow !

This was wired to a 3-pin metal-cased Niphan/Clang-type 5-amp 3-pin 'industrial' type plug (the type with a screw-down retaining ring) and the voltage-selection tapping was set to 110V. There was a "set to 110V" warning label on the packing-case too.

It's still got the red/white/yellow lead, though the 5-amp plug is now replaced by a 13-amp and the selector is set to 240V.

--G6Tanuki.

Aub · 9th Oct 2012, 12:26 pm

Thanks for the replies. I'll fit a new, 3 core, mains lead. Just got to get the lump on to the workbench now!

Cheers

Aub

Radio Wrangler · 9th Oct 2012, 1:41 pm

All of the most unreliable parts in the AR88 are arranged around the edge of the chassis so they are least accessible through the removable cover on the underside of the cabinet.

I'm not sure I can believe this is coincidence.

David

9th Oct 2012, 9:27 am	#1
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,038	AR88D Earthing ( or lack of )? Hello All, My AR88D receiver has, what looks like, the original mains power lead. The mains lead has connections to live and neutral, in the 13A plug, both coloured black and has a black rubber outer. There is no earth connection. When the receiver is connected to my transmitter, it gets a mains earth via the mains earth on the transmitter, but if I use it on its own it doesn't get a mains earth. I've thought of fitting a 3 core mains lead, for safety reasons, but wondered if there is a down side to doing this? Thanks. Aub G4KQL __________________ Life's a long song, but the tune ends too soon for us all.

9th Oct 2012, 10:00 am	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,867	Re: AR88D Earthing ( or lack of )? The AR88 mains side is not to the standard for floating operation and the receiver must be earthed. Relying on other things is always a bit dodgy and having things which require unobvious precautions is risky too. Say I come off my horse this evening and break my neck (I'll try not to). My house will need clearing and there are two AR88s there. Both with 13A plugs on them. Someone is going to try them in the most obvious way, plug one in and see what happens. I don't want to leave anything in an unobvious dangerous condition. The older of my two was rebuilt in 1953 (according to the RAF label stuck to the outside of the right side gusset plate) with a PVC wiring harness, and they replaced the mains cable. PVC, red, black and green cores. The younger AR88 has not been rebuilt and has the original wiring, though someone has replaces the mains lead. The internal stuff is crumbly. I wouldn't trust it without a solid earth and an RCD. I don't think a 2-wire mains cable is original for an AR88 shipped to the UK, anyway David Breaking earths is usually done for breaking up audio hum loops, or for very dodgy floating of oscilloscopes. __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

9th Oct 2012, 12:14 pm	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,996	Re: AR88D Earthing ( or lack of )? You really should use a proper 3-core cable and a proper earth. When I bought my AR88D back in the late-1970s (from a place that used to advertise in the back of "Wireless World" - I forget their name but their ads were always in a narrow column down the full length of the page) it came in an ex-UK-military wooden transit-case with Air Ministry markings and a fairly thick 3-core PVC mains lead - paradoxically colour-coded red, white and yellow ! This was wired to a 3-pin metal-cased Niphan/Clang-type 5-amp 3-pin 'industrial' type plug (the type with a screw-down retaining ring) and the voltage-selection tapping was set to 110V. There was a "set to 110V" warning label on the packing-case too. It's still got the red/white/yellow lead, though the 5-amp plug is now replaced by a 13-amp and the selector is set to 240V. --G6Tanuki.

9th Oct 2012, 12:26 pm	#4
Aub Nonode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 2,038	Re: AR88D Earthing ( or lack of )? Thanks for the replies. I'll fit a new, 3 core, mains lead. Just got to get the lump on to the workbench now! Cheers Aub __________________ Life's a long song, but the tune ends too soon for us all.

9th Oct 2012, 1:41 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,867	Re: AR88D Earthing ( or lack of )? All of the most unreliable parts in the AR88 are arranged around the edge of the chassis so they are least accessible through the removable cover on the underside of the cabinet. I'm not sure I can believe this is coincidence. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done