Sunday, 1 June 2014

Yamaha turntable and audio feed back

Hi Roy,

Earthing via the mains electrical earth is possible but not advisable. If you do encounter an earth leakage situation from another appliance it will be expensive....   This is almost a guaranteed outcome unfortunately, unless you also have a very sensitive surge arrester or similar.




Please read the above at least twice before copying what I have tried below!

Thanks Justin.

The service of a Yamaha turntable was posted some time back.

There is a series of pictures in the link showing the opening and cleaning of the turntable that I bought new from Hamrad in Cape Town.

However I have continued to be wondering why there is feedback when the clear plastic lid is lifted and a record is playing, its fine when I am not touching the player.

This is what the trouble was caused by:

These sets and the audio amplifier by Sony are both connected to 220v electric supply with a two core wire, so positive and negative, there is no ground or earth wire, why?

The turntable has an earth wire which is part of the white and red audio wire loom, the back of the Sony amp has a ground connection which the earth wire connects to but when handling that earth pin with the set powered up gives a lot of noise, why?

The reason was simple, there was no continued earth or ground wire  feed to the buildings power supply.

I took a single wire from the amplifier and then to the power plugs earth pin, unused as there were only the two wires to connect, positive and negative. With the single earth wire connected to the buildings ground system the feedback was gone, simple fix!

How easy was that?


Note, I would suggest that if your not qualified to do such connections or have doubt in your ability to employ someone who is qualified, at all times make changes and connections with the power switched off and with the power supply wall plug removed.

I was going to delete this entire posting as I have obviously made a mistake and posted an error but on thinking about it the post may just stop some person from making the same mistake?

I have removed the ground wire to the domestic power supply earth, next I will run the ground wire to the domestic water supply copper pipes which are in the roof space close by.

The Sony amp and Yamaha turntable were later grounded to the Akai music center, we use the audio tape and CD side on that. This seems to have acted as a large enough ground and so far the feed back has stopped!

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