Yamaha NS-670 woofer repair help needed

[201bk]

Hi,

Long story short I got scamed by seller. And now he won't admit that he has hidden this issue. He says that I have damaged the woofer. I was doing 10wpc tops and it's first time I've heard that you can damage woofer by decentralising it with proper usage.

Everything looks fine with this one faulty unit visually but low bass is distorted like a lot. After a bit of "manual" inspection I have discovered that coil is scratching the magnetic hole. The other woofer is fine.

It looks like it's not centered properly or you need to glue surround to the membrane in one spot because I discovered it played fine when I put my finger with almost no pressure at all to the bottom of membrane right around the spot the surround is glued to it.

I have pushed it a bit manually a few times and it played fine for like a few hours no problem but I guess gravity outdid it.

Now I have two options, try to repair this driver or buy an used working woofer.

Now has anyone done this kind of thing, can you "unglue" and glue this cloth surround and will it survive that's the question. You can remove dust cap fairly easy and glue it back I think.

Will contact a firm which makes surrounds and does the repairs too of drivers here in Poland, they do cloth surrounds I think too. But dunno it's quite unusual shape for a cloth surround. I saw only foam ones with this shape.

It was supposed to be a present for my 30th birthday and now I guess I have a nice furniture until I sort this one out Fortunetly I have a second pair of speakers.

Haven't have found any repair kit but maybe I will be surprised. It was supposed to be a future proof buy because of cloth treaded surrounds but I guess this one worked pretty well for me ...

Thanks in advance for any kind of input really. Much appreciated cuz I want to have a fully functioning set for my Yammie A-960II.

 

[201bk]

So I gotta update from Umifon Września Poland. They said that it's doable. That the should repair it without damaging membrane and surround. I also unscrewed the woofer and checked it up. There's like water condensation on magnet with weird smell of vinegar. Coil casing is probably paper so it swelled up. But they should remake new one with proper specs.

 

[Seventy7]

I hope you can get this sorted! I am a big fan of my NS-690 II's, and most things Yamaha, from that era. Good luck! Keep us posted when you get things worked out... and Happy Birthday!

 

[BillyTheKid]

Replacing the foam and centering the voice coil should fix the problem. That's straightforward.

But what's up with the wet magnet that smells like vinegar ? That's a new one to me.....

 

[201bk]

Replacing the foam and centering the voice coil should fix the problem. That's straightforward.

But what's up with the wet magnet that smells like vinegar ? That's a new one to me.....

The seller it could be his fault I suspect that he stored them in his garage. If not permanently then for a bit. I suspect it's just regular water condensation, dunno about that smell though. Of course he denies it. He says that he stored them in house with heating and only bringed them into his garage at the time of the transaction, he conveniently didn't have proper signal cable and only played me some light sounding vinyl and radio in the garage so I didnt catch it and couldn't play my tunes. So I suspect he did know it was faulty and he gave me a cold shoulder saying its my fault and my amp earlier but after finding out it could be his fault he got defensive.

It's not foam, it's cloth. But Umifon said that it's doable to unglue it without damaging it or membrane.

OK, let's focus on repairs. I will try to unsolder the driver and I will see if magnet gets dry when I get the chance in proper room temperature. And yeah, that's a first one for me seeing a wet magnet smelling like vinegar. Could be there was water in the magnetic hole since coil is ventilated in NS-670 woofer, there's a small hole in the back of the magnet. Coil got hot when I did use them and coil casing swelled up I suspect it has paper casing- that's my guess. Still it's not really my fault. Because I plugged them in hours after buying them and I couldn't have known that there would be this kind of issue.

 

[ehoove]

Your issue is probably that the magnet has shifted which is common on The NS690 series as well. The magnet will need to be removed and re-centered. There are several threads on AK.
Regards,
Jim

I can move this to Yamaha for better exposure if you desire.

@201bk

 

[201bk]

I hope you can get this sorted! I am a big fan of my NS-690 II's, and most things Yamaha, from that era. Good luck! Keep us posted when you get things worked out... and Happy Birthday!

Yeah I hope so too. Well my birthday is like in two months but I saw those NS-670s and I couldn't resist! But thanks anyways!

Your issue is probably that the magnet has shifted which is common on The NS690 series as well. The magnet will need to be removed and re-centered. There are several threads on AK.
Regards,
Jim

I can move this to Yamaha for better exposure if you desire.

@201bk

Oh, thanks Jim for this particular message! Soo.. I've been thinking now if this vinegar smelling water is not water but liquefied glue which was used to glue magnet to the cast basket, it could make a lot of sense tbh! Since surrounds look absolutely mint so does the cabinets so it didn't really make sense. Maybe Umifon won't have to touch dust cap, membrane and surround at all it's worth checking out, this magnet thingie. Yes, yes, do move it into Yamaha subforum. Thanks!

They still have original Yamaha stickers and whatnot plus Quality Check ones too. So it didn't make sense to me. But hey, we learn something new everyday.

I'm finishing my recap of my A-960II so it would be nice to have a proper Yammie+Yammie set.



I can post some vids too. Especially of the faulty woofer and how they properly played before.

Thanks, thanks I really appreciate it,
Michael.

 

[ehoove]

Moved per request. There is a video in this thread that is in Japanese, but the visual should help.
Regards,
Jim

https://audiokarma.org/forums/index.php?threads/prevent-magnet-shift.801451/#post-11127927

 

[201bk]

Moved per request. There is a video in this thread that is in Japanese, but the visual should help.
Regards,
Jim

https://audiokarma.org/forums/index.php?threads/prevent-magnet-shift.801451/#post-11127927

Thanks a lot Jim. So the dust cap needs to be removed either way. If the coil casing will be swollen up it was water if not then magnet shifted. The tech guy should be able to see it, I think. Repair looks fairly simple if someone has the right tools, and this firm I contacted should have them. They do this stuff daily.

 

[saharajim]

Thanks a lot Jim. So the dust cap needs to be removed either way. If the coil casing will be swollen up it was water if not then magnet shifted. The tech guy should be able to see it, I think. Repair looks fairly simple if someone has the right tools, and this firm I contacted should have them. They do this stuff daily.

I had a similar issue when I bought my 690's. I did the repair myself and added some notes to this thread. Hope it helps.
https://audiokarma.org/forums/index...er-shifted-magnet-video.778930/#post-15526668

 

[201bk]

I had a similar issue when I bought my 690's. I did the repair myself and added some notes to this thread. Hope it helps.
https://audiokarma.org/forums/index...er-shifted-magnet-video.778930/#post-15526668

Oh, thanks for pitching in! Looks like adhesive that was used to glue the magnet to the cask basket is faulty after 45 years. Didn't see any rust like in the Japanese vid though on my magnet or the cask basket. But there was some condensation after the magnet shifted and coil got hot after usage could be water or liquefied glue since it smelled weird.

I think after reading this stuff that I should send in two woofers to the repair shop to secure the other one too since it may have the same problem in a while. I've sent this stuff to them in a mail. Along with your post and notes - really appreciate it.

I hope they have some kind of tool to do this because it looks fairly easy to do with proper tools and really hard without them, I guess I will find out in a few hours. This diy dongle you've made looks hardcore, man. Looks the same as the one from Japanese vid - did you copy the same tool? I'm just curious.

Much thanks, @saharajim!

 

[saharajim]

think after reading this stuff that I should send in two woofers to the repair shop to secure the other one too

Agreed. I also secured my second one by coating the outside edges of the magnet to the pole piece.

Looks the same as the one from Japanese vid - did you copy the same tool?

Yes, I copied his design and just modified it to use the bits I had laying around. I'd be interested in knowing how much your repair shop charges to fix yours. I would have paid to have someone fix mine too but I couldn't find anyone to tackle the job. I was told it couldn't be done and to just buy another driver. It was posts on this site that made me think I could do it.

 

[201bk]

I'd be interested in knowing how much your repair shop charges to fix yours. I would have paid to have someone fix mine too but I couldn't find anyone to tackle the job. I was told it couldn't be done and to just buy another driver. It was posts on this site that made me think I could do it

150 Polish zlotys per one woofer. Demagnetizing, uglueing, centering it back, glueing it back and magnetizating it to proper specs. He can even change the magnets polarity so he won't be marking it like you did. He said that he likes a good challenge so he will tackle it.

Its is like 44 CAD for one woofer or 34 USD per one woofer. I said that for that price I will throw in some Ballantines as a thank you because I thought I would pay like 170-200 USD.

 

[saharajim]

150 Polish zlotys per one woofer. Demagnetizing, uglueing, centering it back, glueing it back and magnetizating it to proper specs. He can even change the magnets polarity so he won't be marking it like you did. He said that he likes a good challenge so he will tackle it.

Its is like 44 CAD for one woofer or 34 USD per one woofer. I said that for that price I will throw in some Ballantines as a thank you because I thought I would pay like 170-200 USD.

That is a steel of a deal. He's definitely not doing it for the money. I'd guess that I have 40 hours into it. Fingers crossed that it all works out. Keep us posted.

 

[saharajim]

Ballantines

I had to Google it. I'm more of a rum drinker than scotch. But nice touch.

 

[201bk]

That is a steel of a deal. He's definitely not doing it for the money. I'd guess that I have 40 hours into it. Fingers crossed that it all works out. Keep us posted.

I will.

BTW a lil offtop but it's a bit on point though.
Polish Tonsil remade both of my GDN 25/55 woofers with coil ventilation last year. For my Saba CE 9596 speakers that I have in avatar for like 280 Polish zlotys with shipment.

I only had cask baskets with magnets and old coils, so they remade those woofers almost from from scratch- they also have demagnetized magnets, unglued centered them, glued them back and magnetised them and remade the membranes and surrounds. So it may be regular pricing here in Poland for a woofer service. But they only do their own products so its not a repair all types of units shop. It was a special set made only for export to France by Tonsil in the 80s under the Saba brand.

I had to Google it. I'm more of a rum drinker than scotch. But nice touch.

Check out Nikka from The Barrel and Nikka Blended, a really nice Japanese Whisky. A bonus Yammie in the background to not keep it completely off topic

 

[201bk]

So I have them now at my place. Will try to unscrew and unsolder woofers this weekend, I think. Then packaging and shipment to repair shop and time to center the magnets, I guess.

Anyways, I found out that the crossovers use electrolytic capacitors along with bipolar caps. Could this residue on the back of the magnet with weird vinegar smell... Could it be that it came from some bad cap? Am I on to something here? Any thoughts on this matter? I was quite surprised they used regular caps and not some film ones like mkt/mkp or smth - because they don't loose any capacitance over time. @saharajim @ehoove @BillyTheKid
My Polish speakers you see standing on top of Yammies have film caps and my brothers 1971 Polish speaker has those too.

From what I've seen there are two groups one says that Yamaha engineers used electrolytic caps so I should use those too and they did so for a reason. And second group just says to use the same capacitance and it doesn't make a difference and that I could put in some film ones. What do you think?

And I've been meaning to ask about tweeter driver and midrange driver. If I unscrew those do they fall apart or there are more steps to it? I was planning to replace the wiring with some ofc wires but I've read that I shouldn't touch those drivers at all since it's a pain to put them together if they fall apart. So if there are more steps to it I will maybe upgrade the wires but the change I quess will be minimal at best but its always good to work on your audio eq - if unscrewing them is all it takes to take them apart then I won't touch the wires at all- since it will be all pain and minimal gain ; ).

Thanks in advance for any kind of input. Will update this thread as soon as I will have any new stuff to share! Plus I'm curious to read the answers to my questions and to see if my guess is right about this vinegar smell!

 

[201bk]

First speaker the one that coil is scratching the magnet

Checked the caps there isn't any visual leakage going on so it may not be the "water" from caps it can be something else entirely.

Rust and condensation the one that was mentioned on this forum and the NS-690s video, hmm I wonder what caused this

Had to cut off a bit of wires the two minus ones was almost soldered with coil wire and I was afraid that I would loose it or damage something.

 

[201bk]

Second speaker the one that is working, still

I did stick some cork mat thingies to not scratch them more than they already are - did so with the other speaker too.

Is this wool?


No visual leakage on those caps either. The damping is dry too. So was the one in the other speaker.



Looks more rusted than the one that is scratching! It's a miracle it works, I guess.

 

[201bk]

I guess I didn't see that when I first opened them up. Bonus pic magnet is still wet and smells a bit like vinegar only it is a weaker smell.

Just touched it with my finger and smeared it a bit. What is this?