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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 16th Apr 2021, 10:58 pm   #1
bigfathairyvika
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Default Yamaha Amplifier has magnets glued to sides of relay....

Not something I have seen before, but there are two magnets glued either side of the relay by the contacts.
It appears that they may have been fitted as an aftermarket modification.
But what are they there for?
Arc damping?
The relays are switching audio to speakers.
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Old 16th Apr 2021, 11:08 pm   #2
paulsherwin
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Is this the speaker protection relay? Somebody may have fitted the magnets as a bodge to improve relay operation (though you can buy a new relay for a couple of quid).
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Old 16th Apr 2021, 11:14 pm   #3
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Should have mentioned that....

Yes speaker protection and switching relays.

There are three relays ( three sets of speakers) , one relay I would say is an original matsushita, the two with magnets are DEC. The magnets are no where near the coils but right next to the contacts.
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Old 16th Apr 2021, 11:19 pm   #4
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

You do sometimes get contact problems with protection relays after a couple of decades.
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Old 16th Apr 2021, 11:26 pm   #5
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Yup, contacts do wear and get tarnished... but why the magnets?

Do they magnetise the contacts so they attract each other?

If I get relay contacts that have a problem , I just clean them with acetone and duraglit.
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Old 17th Apr 2021, 12:12 am   #6
paulsherwin
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

All I can think of is that they are intended to make the relays pull down harder. I'm only guessing though, and it might just be some sort of audiophool nonsense.
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Old 17th Apr 2021, 12:55 am   #7
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Rather like archaeologists putting all unknown artefacts down to something used in a religious ceremony, we could see every bit of weirdness added to an audio item as phoolery there may be some justification.

I wonder if there is some other justification. Are the coil ratings written on the case? and do they suit the power supply? It could be as innocent as someone trying to make do with whatever relays they had to hand when some originals failed.

Bodge or foo? not much of a choice. I think I'd find out what the originals were and replace them. Either way, I'd be embarrassed if anyone saw something like that in an amp I'd been associated with.

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Old 17th Apr 2021, 1:14 am   #8
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Quote:
Originally Posted by bigfathairyvika View Post
... are two magnets glued either side of the relay by the contacts.

The relays are switching audio to speakers.
It would seem that the magnets were not intended for any modification of force on the contact by the electromagnetic structure of the relay.

Magnets are sometimes used for polarity sensitive protection contacts to force a longer arc length during the opening of a contact. That said, the magnets would have to be oriented in such a way that the magnetic field was cutting across the direction of an arc, so hopefully the bodge had that aspect correct.

Maybe a keen amateur had just read some commercial blurb on protection cbs/contactors, or just cracked open such a protective device and recovered the magnets from there.
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Old 17th Apr 2021, 2:11 am   #9
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

That echoes my thoughts exactly.

Steve.
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Old 17th Apr 2021, 7:34 am   #10
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Is there some boutique firm out there selling 'Magic Magnets' at silly prices with a little pamphlet telling you where to play around with sticking them? Maybe this amp was someone doing their research before putting them on the market? We'll never know unless someone pops their head above the undergrowth.

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Old 17th Apr 2021, 7:57 am   #11
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

The same magnet fitments were discussed on audiokarma in 2018, the OP was about a Nikko Alpha 440 but by about the 5th post someone was reporting that these fitted OEM by Yamaha.

https://audiokarma.org/forums/index....-relay.814043/

The thread includes pictures.
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Old 17th Apr 2021, 9:17 am   #12
Malcolm G6ANZ
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

It looks as though magnets on relays are meant for high current applications:
https://www.durakoolrelays.com/infor...-why-use-them/
I'd be surprised if they have any effect at audio power levels
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Old 17th Apr 2021, 9:35 am   #13
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

what is the model number of the amp
John.
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Old 17th Apr 2021, 10:04 am   #14
turretslug
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Could the amp have a fault, e.g. slight/intermittent/unstable DC offset that causes the protection circuit to operate and open the contacts, or stop them closing in the first place, or maybe the amp is OK and the protection circuit is faulty, and the magnets are a bodge to keep the contacts closed? They may have shifted them about until they closed the contacts successfully.
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Old 17th Apr 2021, 10:42 am   #15
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Magnets are often used on heavy current contactors to "blow-out" any arc that may develop when the contactor is breaking a large current. The magnets serve to direct the arc plasma away from the contacts thus reducing contact erosion due to the very high local temperatures encountered.

John
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Old 17th Apr 2021, 10:53 am   #16
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Most so called 'speaker protection' relays don't stand much chance against an output device going dead short. They often aren't rated sufficiently to break the DC current and may just arc until the contacts burn away or the PSU blows a fuse (or the speaker goes open circuit...).

Shorting out the speakers using changeover contacts will give them a fighting chance even if the relay doesn't survive, and at least the arcing into the short will likely blow the fuse quicker.

Blowout magnets may help to reduce the arcing problem, but are usually fitted inside the relay. If Yamaha have indeed glued them to the outside of a normal relay, this is likely an attempt at a lower cost solution then a much larger and correctly rated relay.

A photo from the previously mentioned AudioKarma thread alledgedly showing a number of relays from Yamaha with magnets attached:-

Click image for larger version

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It's seems pretty unlikely it could have had any value as a marketing gimmick, and since it still adds a cost to them over the basic relay one might imagine/hope they did the appropriate testing to prove any benefit

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Old 17th Apr 2021, 3:40 pm   #17
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

I have delved a little deeper...
The amp is a MX-1000 Yamaha rated around 250W per channel.
The relays ARE original.
Removing the duct tape over the magnets there is a black fibre tape underneath. Which is probably original.
So as has been mentioned, the magnets were very likely fitted by Yamaha!
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Old 17th Apr 2021, 5:31 pm   #18
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

The Japanese marketing departments are always on the lookout for some new selling point. I bought a new CD player a few years ago. Sony made a big thing about R-core mains transformers and there being TWO of them as well as the chassis being copper plated.

Did they really believe this made any difference?

I wonder if Yamaha's little magnets made it into their brochure?

If no-one knows about the foo, how can it work?

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Old 17th Apr 2021, 9:14 pm   #19
Trigon.
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Quote:
Originally Posted by bigfathairyvika View Post
Removing the duct tape over the magnets there is a black fibre tape underneath.
A picture of a Yamaha speaker protection board from an eBay listing, showing what appears to be the tape described wrapped around the relays:-

Click image for larger version

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ID:	232013

Cheers
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Old 17th Apr 2021, 9:26 pm   #20
bigfathairyvika
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Default Re: Yamaha Amplifier has magnets glued to sides of relay....

Quote:
Originally Posted by Trigon. View Post
Quote:
Originally Posted by bigfathairyvika View Post
Removing the duct tape over the magnets there is a black fibre tape underneath.
A picture of a Yamaha speaker protection board from an eBay listing, showing what appears to be the tape described wrapped around the relays:-

The relays exactly match the ones in the MX-1000.

Mark
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