Record player earthing. - UK Vintage Radio Repair and Restoration Discussion Forum

Reproman · 8th Dec 2005, 6:57 pm

Hello everyone,

I have a Pilot record player (1960's) that I am restoring and I wanted to get rid of the old mains flex (black and red wires) and replace it with standard three core cable.

I wired up the live and neutral correctly and it worked fine, but when I wired up the earth wire to the record player mech chassis assembly, it caused the mains circuit breaker to trip.

What is causing this to happen?, I have checked the mech chassis for any significant leakage and there is none. I hope you can solve this mystery for me.

Kind Regards

( Note from Archivist.....for the benefit of anybody new to the vintage technology hobby, please be familiar with the safety issues concerning the wiring - and wiring polarity - of potentially dangerous 'live chassis' AC/DC equipment )

Nickthedentist · 8th Dec 2005, 7:01 pm

Hello!

What model is this? What valves does it use?

Are you sure it's not an "AC/DC" or "universal" model, in other words, one that has no mains transformer, and uses U-series valves with the filaments wired in series?

If so, it will have the neutral (black or blue) mains wire connected straight to the amp chassis, so if you connect the earth (green or green/yellow) wire to the chassis as well, the RCD in your consumer unit will trip.

If it is one of these, all you should do is use a modern 2-core flex, making sure the neutral wire (and not the live) is connected to chassis), and always use it on an RCD-protected socket.

You should also ensure that the knobs are securely fixed, and that the capacitors that isolate the deck/cartridge from the amp are sound, and preferably replace them with modern ones of the right rating.

Nick

Reproman · 8th Dec 2005, 8:16 pm

Hello,

The record player is a Pilot model RC123, the positive and negative wires go straight to the on/off/volume switch, the output valves are UCL82's and the rectifier valve is a UY85, all caps have been replaced, along with a few bad resistors.

I don't think it's a DC set,as the amp chassis is not live and there is a transformer installed.

Kind Regards

mickjjo · 8th Dec 2005, 8:27 pm

If you look at the circuit of the Pilot RC123, in post *14 of this thread:-

https://www.vintage-radio.net/forum/...ighlight=pilot

This machine has a live chassis, and as Nick said, was not designed to be earthed.

.

Regards, Mick.

Nickthedentist · 8th Dec 2005, 8:51 pm

Quote:

Originally Posted by Reproman

the output valves are UCL 82's and the
rectifier valve is a UY 85,all caps have been replaced,along with a few bad resistors, I don't think it's a DC set,as the amp chassis is not live and there is a transformer installed.

Aha!

Those valve numbers are the giveaway, they start with U, which does indicate an AC/DC model with no mains transformer.

The transformer you can see must be the audio output transformer

Here's the link to the circuit that Mick posted: https://www.vintage-radio.net/forum/...achmentid=2101

It shows clearly that one of the mains wires goes, via the on/off switch (SW2), straight to the chassis. The transformer is T1, which couples the output valve to the speaker.

Note that the gram chassis is connected to the amp chassis by C13 - you should make sure that this is in good condition as if it shorts, it will connect the gram chassis to mains neutral, or if the the mains socket is wired backwards (not uncommon), to mains live

With the machine unplugged, set your meter to its lowest resistance range and connect one terminal to the amp chassis. Make sure that the on/off switch is set to on, then touch the other terminal to each of the wires in the mains lead. You should read a low resistance to one of them, the blue one if the wire has been fitted the right way round.

Let us know what you find.

Nick

Reproman · 8th Dec 2005, 9:34 pm

Hello

Many thanks for the info,this why it always wise to ask people who know more about electrics than yourself.

Was DC used in this country in the 1960's, or was this model designed for export? I had an HMV portable record player of the same vintage which had three wires coloured white!, at some point in the past someone wired the mains lead the wrong way round and as a consequence I got a 240 volt jolt from the pickup arm!!! .

Kind Regards

Nickthedentist · 8th Dec 2005, 9:56 pm

Quote:

Originally Posted by Reproman

was DC used in the country in the 1960's,or was this model designed for export

DC was very rare by the 60s in the UK, but radios and record players like this were still produced because they were cheaper to make than AC-only ones, because the expensive transformer could be done away with, and replaced by a cheap "dropper resistor" instead.

But AC/DC sets are riskier (as you've found

) and run hotter so are somewhat less reliable than their AC-only cousins.

Assuming you've got broadband, download the classic book "Radio Repair, Questions & Answers" by Les Lawry-Johns from here http://vintage-radio.info/docs/index.htm and read Chapter 6 (starts on page 58 of the PDF).

Nick.

8th Dec 2005, 6:57 pm	#1
Reproman Retired Dormant Member Join Date: Nov 2005 Location: Southampton Posts: 17	Record player earthing. Hello everyone, I have a Pilot record player (1960's) that I am restoring and I wanted to get rid of the old mains flex (black and red wires) and replace it with standard three core cable. I wired up the live and neutral correctly and it worked fine, but when I wired up the earth wire to the record player mech chassis assembly, it caused the mains circuit breaker to trip. What is causing this to happen?, I have checked the mech chassis for any significant leakage and there is none. I hope you can solve this mystery for me. Kind Regards ( Note from Archivist.....for the benefit of anybody new to the vintage technology hobby, please be familiar with the safety issues concerning the wiring - and wiring polarity - of potentially dangerous 'live chassis' AC/DC equipment ) Last edited by Darren-UK; 23rd Jul 2007 at 10:05 pm. Reason: General tidying and note added.

8th Dec 2005, 7:01 pm	#2
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,866	Re: Record player earth problem Hello! What model is this? What valves does it use? Are you sure it's not an "AC/DC" or "universal" model, in other words, one that has no mains transformer, and uses U-series valves with the filaments wired in series? If so, it will have the neutral (black or blue) mains wire connected straight to the amp chassis, so if you connect the earth (green or green/yellow) wire to the chassis as well, the RCD in your consumer unit will trip. If it is one of these, all you should do is use a modern 2-core flex, making sure the neutral wire (and not the live) is connected to chassis), and always use it on an RCD-protected socket. You should also ensure that the knobs are securely fixed, and that the capacitors that isolate the deck/cartridge from the amp are sound, and preferably replace them with modern ones of the right rating. Nick Last edited by Nickthedentist; 8th Dec 2005 at 7:06 pm.

8th Dec 2005, 8:16 pm	#3
Reproman Retired Dormant Member Join Date: Nov 2005 Location: Southampton Posts: 17	Re: Record player earth problem Hello, The record player is a Pilot model RC123, the positive and negative wires go straight to the on/off/volume switch, the output valves are UCL82's and the rectifier valve is a UY85, all caps have been replaced, along with a few bad resistors. I don't think it's a DC set,as the amp chassis is not live and there is a transformer installed. Kind Regards Last edited by Darren-UK; 13th Jun 2007 at 12:41 am. Reason: General tidying.

8th Dec 2005, 8:27 pm	#4
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Record player earth problem If you look at the circuit of the Pilot RC123, in post *14 of this thread:- https://www.vintage-radio.net/forum/...ighlight=pilot This machine has a live chassis, and as Nick said, was not designed to be earthed. . Regards, Mick.

8th Dec 2005, 9:34 pm	#6
Reproman Retired Dormant Member Join Date: Nov 2005 Location: Southampton Posts: 17	Re: Record player earth problem Hello Many thanks for the info,this why it always wise to ask people who know more about electrics than yourself. Was DC used in this country in the 1960's, or was this model designed for export? I had an HMV portable record player of the same vintage which had three wires coloured white!, at some point in the past someone wired the mains lead the wrong way round and as a consequence I got a 240 volt jolt from the pickup arm!!! . Kind Regards Last edited by Darren-UK; 13th Jun 2007 at 12:46 am. Reason: General tidying.