Record Decks - to earth or not? - UK Vintage Radio Repair and Restoration Discussion Forum

harvestgold · 26th May 2007, 11:53 am

Hi! I have just finished restoring a Marconiphone record player (from approx 1969) as a favour for somebody I know. The old mains lead was a bit scabby, so I have replaced it with a new one (together with new, legal plug!). My question is, would it be good practice to earth the BSR turntable? The single-valve amp chassis is earthed already, but the deck isn't. Also, as the motor body and the deck are separated by rubber mounts, would it be sensible to earth this too? What do others do?

I would normally leave things as they were for myself, but as this is for someone else, I need to be a bit careful.

Thanks, Neil.

Stewart · 26th May 2007, 1:13 pm

Just out of interest, what is the model number of this player? I only ask because most of the BRC valve players of this era that come to mind used U series valves and the AC/DC technique - with understandably just a two core cable.

harvestgold · 26th May 2007, 2:46 pm

Hi Stewart,

It's a Marconi Model 4026. The chassis was definitely earthed - the cable looks like it was the original one (old colours etc.).

All it needed to get it going was the usual grease removal / relube of the BSR deck and a spot of switch cleaner on the volume pot. For a single valve set, it gives out quite a decent volume! I have never come across the turntable before, it has a little peg which rises up at the side of the platter to determine record size rather than the more conventional method.

Stewart · 26th May 2007, 5:24 pm

Indeed - a transformer fed ECL86 circuit! Sorry to have doubted you...but you can't be too careful!

In which case I personally can't see any reason not to earth the motor and turntable metalwork.

There is a slight chance of creating a earth loop and getting hum problems given the pick-up ground probably goes to the turntable metalwork as well as the amplifier chassis - but at the gain levels involved I don't think it will be an issue..

Given you mention the amplifier chassis having an earth connection already - does that not earth the turntable via the pickup screen? Links on the centre three tags on the turntable connection tag-strip would suggest so if present.

That IS an unusual BSR changer...I've yet to see one in the flesh! It's the UA45 model. I'm trying to think of a good reason for them making such a variation over the standard models - and failing though!

Paul Stenning · 26th May 2007, 9:24 pm

I would earth the deck, for safety. Should a fault cause the deck to become live you wouldn't be very popular (plus it would fail a PAT test if not earthed).

The motor body doesn't matter as it can't be touched when the record player is being used normally.

Trevor · 27th May 2007, 12:16 am

Earthing.....

The worst that can happen if you do is an earth loop...... the worst that can happen if you don't is death.

Regards,
Trev.

harvestgold · 27th May 2007, 11:37 am

Thanks for that. I always tend to err on the side of safety, but I wondered if earthing could cause any problems. I have just tested it with and without the turntable earth lead fitted and there is no difference to the sound. Was it just penny-pinching which dictated no turntable earthing in the original design I wonder?

Stewart - I didn't realise this was such an unusual deck - I know I have never seen one before though! The deck functions well (as most BSRs do when they have had a bit of lubrication). I have quite a few variations of BSR autochangers from the early Monarchs to the last plasticky things - maybe I should start collecting all the versions and start a mini museum. I know they aren't popular decks in record collectors' circuits or for hifi afficianados, but I have always had a soft spot for them, having always had one or two around when I was growing up - there is something about the sound of them firing up that just takes me back. . .

Thanks! Neil.

Focus Diode · 27th May 2007, 6:04 pm

I had an interesting problem with my Rotel RP2500 turntable. This came with two core mains cable which I thought was unusual. At the time I used it with my Technics SU-Z150 amplifier, which is also two cored although did have a provision for Earthing the turntable.

The results with this combination resulted in a background buzz with a "brush tingle" feel on the turntable's metal parts, clearly akin to leaving the Earth disconnected in any 3-cored appliance when working normally.

I replaced the turntable's flex with a 3-core one which solved both problems.

The reasons for this are interesting: In 1975 when the turntable was made non Earthed amplifiers were just about unheard of. The turntable was dependent on the Earth connection at the amplifier, which was proven on trying a Pioneer 3-cored amplifier with the turntable before fitting the 3-core flex to the latter!

The turntable is now connected to my Leak Stereo 30 with no need to fit the turntable's original Earth lead to it, both now being 3-cored of course. Thec Technics is now used as a main amplifier.

Brian R

peter_sol · 30th May 2007, 11:21 am

Hi
The motors are double insulated with no need to earth and if the chassis is earthed so will the deck be through the screen of the input lead so should be ok.
Regards
Peter.

plumbweiss · 10th Jun 2007, 8:37 pm

Quote:

The results with this combination resulted in a background buzz with a "brush tingle" feel on the turntable's metal parts, clearly akin to leaving the Earth disconnected in any 3-cored appliance when working normally.

There's alot of mention of this on this forum. Before the advent of y-connected mains filter capacitors to meet EMC / CE requirements, any unearthed equipment which exhibits a marked, preceptible leakage to accessible conductive parts should be regarded as faulty! It doesnt matter if its AC only, AC/DC or whatever. If your turntable deck requires an additional earth adding to prevent a shock, then there's something gone leaky or breaking down....your new earth will simply mask the fault and is not a long-term answer.

Mersey_Swimmer · 11th Jun 2007, 12:37 am

Quote:

Originally Posted by plumbweiss

If your turntable deck requires an additional earth adding to prevent a shock, then there's something gone leaky or breaking down....your new earth will simply mask the fault and is not a long-term answer.

I'm sure that in my days as an audio engineer (early '70s) I came across earth leakage via the motor's microswitch mounted in the autochanger mechanism. Might be an idea to check out the switch and associated wiring for damaged insulation.

Re. hum loops. Easy to prevent. Thoroughly ground the autochangers' metalwork to the mains earth, but make sure the "signal" earth (ie cartridge "cold" connection and cable screen) is not connected to any metalwork. This should be grounded only via the amplifier's input.

Pete

Trish · 11th Jun 2007, 8:43 am

This is where I feel that the 'rules' that relate to PAT testing needs to be followed.. If the turntable has exposed metalwork that can be touched. And what it is connected to (be it control circuitry or motor) isn't double insulated or isolated via a transformer. Then it should be earthed.

As for Hum / Earth loops. Most stand alone turntables have a seperate earth lead that connects to a terminal on the amplifier.. The point of this is to create a star earth system, which avoids hum loops. Star earthing is standard practice in sound studios.

Once you have got your head around what earth loops are about. You are then on the way to getting it right everytime. Regardless of what the equipment is.. There is lots of technical information available about this if you do a quick search.

If in doubt ... Earth it. Your life is valuable.

Trish

plumbweiss · 17th Jun 2007, 9:01 pm

Trish is right of course. I suppose the bone of contention is that alot of our beloved old stuff isn't made to modern standards...so do we make it conform, or leave it? Since safety is the main issure regarding 'modern' standards, then I reckon it's best to err on the side of safety. I shan't go on since this approach has been covered elsewhere....

However, even 60 year-old stuff was made such that you wouldn't get a shock (no matter how small!) if it was all working correctly...any subsequent problems are all about deterioration of insulation rather than downright design faults. So we must now address these deterioration issues (and potential for deterioration) in the 21st century!

If you are worried about introducing hum-loops on turntables (a real problem with adding extra safety earths), then why not add an audio isolating transformer between pick-up and pre amp? Maplin, CPC and goodness-who-else do these for a couple of quid or so and are about half-an-inch square so will fit anywhere. I've used several of these when renovating vintage organs where the owner wants to interface them to modern mixing desks for studio use.

26th May 2007, 11:53 am	#1
harvestgold Hexode Join Date: Jul 2005 Location: Worcestershire, UK. Posts: 282	Record Decks - to earth or not? Hi! I have just finished restoring a Marconiphone record player (from approx 1969) as a favour for somebody I know. The old mains lead was a bit scabby, so I have replaced it with a new one (together with new, legal plug!). My question is, would it be good practice to earth the BSR turntable? The single-valve amp chassis is earthed already, but the deck isn't. Also, as the motor body and the deck are separated by rubber mounts, would it be sensible to earth this too? What do others do? I would normally leave things as they were for myself, but as this is for someone else, I need to be a bit careful. Thanks, Neil. Last edited by Darren-UK; 15th Jul 2011 at 1:48 pm.

26th May 2007, 1:13 pm	#2
Stewart Retired Dormant Member Join Date: Jul 2003 Location: N.E. Surrey, UK. Posts: 361	Re: Turntables - to earth or not? Just out of interest, what is the model number of this player? I only ask because most of the BRC valve players of this era that come to mind used U series valves and the AC/DC technique - with understandably just a two core cable.

26th May 2007, 2:46 pm	#3
harvestgold Hexode Join Date: Jul 2005 Location: Worcestershire, UK. Posts: 282	Re: Turntables - to earth or not? Hi Stewart, It's a Marconi Model 4026. The chassis was definitely earthed - the cable looks like it was the original one (old colours etc.). All it needed to get it going was the usual grease removal / relube of the BSR deck and a spot of switch cleaner on the volume pot. For a single valve set, it gives out quite a decent volume! I have never come across the turntable before, it has a little peg which rises up at the side of the platter to determine record size rather than the more conventional method. Attached Thumbnails

26th May 2007, 5:24 pm	#4
Stewart Retired Dormant Member Join Date: Jul 2003 Location: N.E. Surrey, UK. Posts: 361	Re: Turntables - to earth or not? Indeed - a transformer fed ECL86 circuit! Sorry to have doubted you...but you can't be too careful! In which case I personally can't see any reason not to earth the motor and turntable metalwork. There is a slight chance of creating a earth loop and getting hum problems given the pick-up ground probably goes to the turntable metalwork as well as the amplifier chassis - but at the gain levels involved I don't think it will be an issue.. Given you mention the amplifier chassis having an earth connection already - does that not earth the turntable via the pickup screen? Links on the centre three tags on the turntable connection tag-strip would suggest so if present. That IS an unusual BSR changer...I've yet to see one in the flesh! It's the UA45 model. I'm trying to think of a good reason for them making such a variation over the standard models - and failing though!

26th May 2007, 9:24 pm	#5
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Re: Turntables - to earth or not? I would earth the deck, for safety. Should a fault cause the deck to become live you wouldn't be very popular (plus it would fail a PAT test if not earthed). The motor body doesn't matter as it can't be touched when the record player is being used normally. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

27th May 2007, 12:16 am	#6
Trevor Octode Join Date: Aug 2006 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 1,082	Re: Turntables - to earth or not? Earthing..... The worst that can happen if you do is an earth loop...... the worst that can happen if you don't is death. Regards, Trev. Last edited by Darren-UK; 13th Jan 2008 at 10:56 pm. Reason: Made comprehensible.

27th May 2007, 11:37 am	#7
harvestgold Hexode Join Date: Jul 2005 Location: Worcestershire, UK. Posts: 282	Re: Turntables - to earth or not? Thanks for that. I always tend to err on the side of safety, but I wondered if earthing could cause any problems. I have just tested it with and without the turntable earth lead fitted and there is no difference to the sound. Was it just penny-pinching which dictated no turntable earthing in the original design I wonder? Stewart - I didn't realise this was such an unusual deck - I know I have never seen one before though! The deck functions well (as most BSRs do when they have had a bit of lubrication). I have quite a few variations of BSR autochangers from the early Monarchs to the last plasticky things - maybe I should start collecting all the versions and start a mini museum. I know they aren't popular decks in record collectors' circuits or for hifi afficianados, but I have always had a soft spot for them, having always had one or two around when I was growing up - there is something about the sound of them firing up that just takes me back. . . Thanks! Neil.

27th May 2007, 6:04 pm	#8
Focus Diode Octode Join Date: Jan 2006 Location: Borough of Gateshead, UK. Posts: 1,420	Re: Turntables - to earth or not? I had an interesting problem with my Rotel RP2500 turntable. This came with two core mains cable which I thought was unusual. At the time I used it with my Technics SU-Z150 amplifier, which is also two cored although did have a provision for Earthing the turntable. The results with this combination resulted in a background buzz with a "brush tingle" feel on the turntable's metal parts, clearly akin to leaving the Earth disconnected in any 3-cored appliance when working normally. I replaced the turntable's flex with a 3-core one which solved both problems. The reasons for this are interesting: In 1975 when the turntable was made non Earthed amplifiers were just about unheard of. The turntable was dependent on the Earth connection at the amplifier, which was proven on trying a Pioneer 3-cored amplifier with the turntable before fitting the 3-core flex to the latter! The turntable is now connected to my Leak Stereo 30 with no need to fit the turntable's original Earth lead to it, both now being 3-cored of course. Thec Technics is now used as a main amplifier. Brian R

30th May 2007, 11:21 am	#9
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Turntables - to earth or not? Hi The motors are double insulated with no need to earth and if the chassis is earthed so will the deck be through the screen of the input lead so should be ok. Regards Peter.

11th Jun 2007, 8:43 am	#12
Trish Retired Dormant Member Join Date: Apr 2005 Location: Reading, Berkshire, UK. Posts: 95	Re: Turntables - to earth or not? This is where I feel that the 'rules' that relate to PAT testing needs to be followed.. If the turntable has exposed metalwork that can be touched. And what it is connected to (be it control circuitry or motor) isn't double insulated or isolated via a transformer. Then it should be earthed. As for Hum / Earth loops. Most stand alone turntables have a seperate earth lead that connects to a terminal on the amplifier.. The point of this is to create a star earth system, which avoids hum loops. Star earthing is standard practice in sound studios. Once you have got your head around what earth loops are about. You are then on the way to getting it right everytime. Regardless of what the equipment is.. There is lots of technical information available about this if you do a quick search. If in doubt ... Earth it. Your life is valuable. Trish

17th Jun 2007, 9:01 pm	#13
plumbweiss Retired Dormant Member Join Date: Nov 2006 Location: Manchester, UK. Posts: 157	Re: Turntables - to earth or not? Trish is right of course. I suppose the bone of contention is that alot of our beloved old stuff isn't made to modern standards...so do we make it conform, or leave it? Since safety is the main issure regarding 'modern' standards, then I reckon it's best to err on the side of safety. I shan't go on since this approach has been covered elsewhere.... However, even 60 year-old stuff was made such that you wouldn't get a shock (no matter how small!) if it was all working correctly...any subsequent problems are all about deterioration of insulation rather than downright design faults. So we must now address these deterioration issues (and potential for deterioration) in the 21st century! If you are worried about introducing hum-loops on turntables (a real problem with adding extra safety earths), then why not add an audio isolating transformer between pick-up and pre amp? Maplin, CPC and goodness-who-else do these for a couple of quid or so and are about half-an-inch square so will fit anywhere. I've used several of these when renovating vintage organs where the owner wants to interface them to modern mixing desks for studio use.