Garrard 4HF voltage on chassis, earth leakage?

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Malcolm7908
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Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 02 Feb 2019 12:02

I’ve been using Vinyl Engine resources to Help me in the renovation of my Garrard 4HF (H) Schedule number 55540/2. But have now found a problem which may very well be terminal and I cannot find any previous post on the subject.
The deck is wired to the mains without an earth. I noticed that when the supply to the deck was live but the deck switched off there was a “furry” feeling in my fingers when the chassis was lightly touched. I couldn’t detect anything when the deck was running or unplugged from the mains. Having come across this many years ago I tested with a volt meter. With the setting on AC and holding one probe I tested over the chassis with the other probe and when not running it had a voltage of about 38v and when running a voltage of 7v.
The speed adjuster and spark arrester needed renewing and was duly carried out ( I thought it would resolve the problem) but the voltages still persist.
Before I embark on a systematic dismantling of the electrical system has anyone come across this problem or any suggestions?

One thing I did notice in some posts was the speculation of thread sizes used. As far as I can tell they are all BA threads as used in model engineering, fairly easy to get in the UK but I’m not so sure about our American friends.

Thank you, Malcolm

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Chiltern » 02 Feb 2019 14:29

Disconnect the spark arrester (capacitor + resistor) and see if you still have these voltages.

Alan

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 02 Feb 2019 19:22

Hi Alan.
With the spark arrester disconnected I’m getting 34v with the deck switched off. I didn’t attempt to start the deck.
Malcolm

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by A70BBen » 03 Feb 2019 01:49

Where are you located? If in the USA, with its unbalanced single-phase power feed, reverse the AC lind cord and try again.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Chiltern » 03 Feb 2019 10:26

Wiring diagram attached. Swapping the feed a good start. If you connect an earth does it trip your rcd?

Alan
4HF wiring diagram.jpeg
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Malcolm7908
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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 03 Feb 2019 10:55

To follow on from Alan’s suggestion and to answer your’s Ben.
With the switch dismantled and removed, the mains connector checked and unbolted (but not disconnected) and the motor assembly removed from the chassis and isolated I rechecked. There was still a 35v reading on the motor assembly and a 7v reading on the chassis.
I saw that the live feed went to the motor windings. The mains connector had no indication as to which side the live and return should go so I swapped them over. This immediately resolved the voltage problem. I put the deck back together.
There is now a voltage of 1-2v when the deck is not running and a voltage of 23v when it is.
Oh nearly forgot , I live in the UK.
I wonder has anyone checked their deck for residual voltages?
Maybe it’s the nature of the beast?

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 03 Feb 2019 11:55

Thanks, Alan, for the diagram. I had seen it on this site.
When I replaced the speed controller I used an Ohmite equivalent so only had to cater for its different size and fittings. I’ve just got to drill out the old knob then not even the fixing nut will be seen.
I replaced the flex with 3 core and connected the earth. No it doesn’t trip the RCD and the voltage is 6v on and off.
I noticed that the house earth is running at 6v anyway.
It seems like it’s a case of ignoring the idiosyncrasies of the electrics. I’d be interested to know what other decks are like.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Chiltern » 03 Feb 2019 13:06

I think that you have answered your own question.
I have a couple of 4HF , just checked one, reading 0v running or not.

No voltage on the house earth

Alan

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 03 Feb 2019 13:14

Thank you for your time and trouble. At least with all the dismantling I did I have cleaned parts that I hadn’t intended to and bits have been checked throughout.
All I have to do now is work out a way of refixing the broken arm rest in its mounting.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by A70BBen » 04 Feb 2019 02:02

I have a feeling that nothing may be wrong. You are measuring leakage with a high impedance instrument (your voltmeter). At a very high impedance, even a tiny bit of leakage within normal range could show up as what looks like an alarmingly high voltage.

Measure the resistance between chassis and each live pin of the power cord. It should be very high in the megohms.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 06 Feb 2019 11:14

Sorry for the delay in replying. Yes you are right. In which case it shows how sensitive my fingers were to the voltage in the first place.
Thank you.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Thermonic » 09 Feb 2019 07:49

My 4HF is earthed to the nut on the motor. My friend has the earlier version and his is grounded to the motor plate. I recently changed to the ohmite unit also and chopped and drilled the knob. The shaft on the ohmite is a bit longer so factor this in before you chop it. Regards.

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Malcolm7908 » 09 Feb 2019 12:19

When I replaced the speed controller housing I fitted it on some standoffs. This had a twofold result of making the spindle length approximately similar and hiding the fixing locknut. But it didn’t protrude further down than the spindle housing.
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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by Thermonic » 09 Feb 2019 23:52

Good idea. How robust is it? Does it wobble?

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Re: Garrard 4HF voltage on chassis, earth leakage?

Post by smee4 » 10 Feb 2019 01:17

A70BBen wrote:
04 Feb 2019 02:02
I have a feeling that nothing may be wrong. You are measuring leakage with a high impedance instrument (your voltmeter). At a very high impedance, even a tiny bit of leakage within normal range could show up as what looks like an alarmingly high voltage.

Measure the resistance between chassis and each live pin of the power cord. It should be very high in the megohms.
I agree. If it will run with the earth attached and not trip anything, I think I would feel fairly safe.

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