NS1000 Woofer magnet shift
- Thread starter srinath
- Start date
Yes yes yes yes yes ........ Wowee...
Did you get it aligned ? Did it work ? Can you loan me that ?
Or can I drill 3-4 holes in a car brake drum and put the woofer magnet side down and - basically the same rig but woofer facing up, and the wall of the brake drum preventing the magnet from getting away from our squeezing the plate/basket toward it.
Or if this did work, I'll just make this or a facsimile there of - but please can I borrow it ... please ... Its just coming to NC. I used to live in Houston TX. Should have started on audio back then.
Thanks.
Srinath.
Did you get it aligned ? Did it work ? Can you loan me that ?
Or can I drill 3-4 holes in a car brake drum and put the woofer magnet side down and - basically the same rig but woofer facing up, and the wall of the brake drum preventing the magnet from getting away from our squeezing the plate/basket toward it.
Or if this did work, I'll just make this or a facsimile there of - but please can I borrow it ... please ... Its just coming to NC. I used to live in Houston TX. Should have started on audio back then.
Thanks.
Srinath.
It is not mine, but found a pic in a quest to repair a 890 woofer that I have that is locked up. I have the tools and ability to build the jig.
I have zero knowledge and/or experience repairing speakers... so if I built the jig would have no clue how to use it properly.
I have zero knowledge and/or experience repairing speakers... so if I built the jig would have no clue how to use it properly.
I am in process of reworking a pair of these now.
With all the corrosion I find in these magnet assemblies- I would never rely on just "jigging" and re-gluing one of these Yamaha woofers, as a long-term solution. THAT CORROSION NEEDS TO BE ELIMINATED, ALONG WITH ALL THE ORIGINAL GLUE- or you are asking for more moisture wicking, and the same problem again later.
It takes me about a half-hour to use a Dremel sanding drum, to get rid of all the rust on one of these, after carefully scraping (almost chiseling) away the old glue. But, once it's done this way- it should work pretty much forever, in any practical sense...
Regards,
Gordon.
With all the corrosion I find in these magnet assemblies- I would never rely on just "jigging" and re-gluing one of these Yamaha woofers, as a long-term solution. THAT CORROSION NEEDS TO BE ELIMINATED, ALONG WITH ALL THE ORIGINAL GLUE- or you are asking for more moisture wicking, and the same problem again later.
It takes me about a half-hour to use a Dremel sanding drum, to get rid of all the rust on one of these, after carefully scraping (almost chiseling) away the old glue. But, once it's done this way- it should work pretty much forever, in any practical sense...
Regards,
Gordon.
GordonW - You're not too far from me in the ATL (I run between Columbia SC and Charlotte NC. Will be able to bring them to you and getting them back in person.
Would I be able to enlist you if needed in my VC swap on these ? I ordered the VC, mine are open. The magnet shift can be alleviated when you do the VC - if you get it close right ?
I will be cleaning all corrosion and the old glue off, sealing the outer edge as well with the epoxy.
Thanks.
Srinath.
Would I be able to enlist you if needed in my VC swap on these ? I ordered the VC, mine are open. The magnet shift can be alleviated when you do the VC - if you get it close right ?
I will be cleaning all corrosion and the old glue off, sealing the outer edge as well with the epoxy.
Thanks.
Srinath.
And the VC I bought does not fit. Looking at winding my own shortly.
But I also have another problem, one which can not use this solution.
In my initial photos I could not quite put my finger on it, hence I didn't document it. But the magnet did not shift. the pole piece and end cap shifted. Of course the magnet has to come off anyway, and the pole piece can be centered in the magnet with spacers, and glued back on of course.
Here is my pole piece now, after some repeated handling - I'd say its got significantly worse.
The first is my original pic, the second is as it is now.
Cool.
Srinath.
But I also have another problem, one which can not use this solution.
In my initial photos I could not quite put my finger on it, hence I didn't document it. But the magnet did not shift. the pole piece and end cap shifted. Of course the magnet has to come off anyway, and the pole piece can be centered in the magnet with spacers, and glued back on of course.
Here is my pole piece now, after some repeated handling - I'd say its got significantly worse.
The first is my original pic, the second is as it is now.
Cool.
Srinath.
Attachments
Jig for both ? you mean Voice coil and aligning this ?
I can align the pole piece in the bigger donut with a plastic spacer set, those tolerances are huge. Also we're dealing with metal on metal measurements so its easier as well.
I got to make the VC for it, that's my biggest issue.
Cool.
Srinath.
I can align the pole piece in the bigger donut with a plastic spacer set, those tolerances are huge. Also we're dealing with metal on metal measurements so its easier as well.
I got to make the VC for it, that's my biggest issue.
Cool.
Srinath.
If it uses 30 awg wire, I calculate about 70 turns, for a 50 foot length and 5 ohm DCR which translates to 25 X 2 turns and at .254mm dia the VC winding length is 6.35mm. Is that all this thing has, I would have thought it had more. But the part sticking in the magnet gap seems to be 3-4 mm. So maybe the 6mm is fine. Does it have 30 awg wire though > Does anyone know.
Cool.
Srinath.
Cool.
Srinath.
I have not got anywhere near winding this coil, but a pair appeared too cheap to pass up. And yes needs repair. And hoping its got the 5ohm they claimed it had.
Now I have a couple questions about the magnet shift for people who have opened em.
1. Do you see that the pole piece - the outer cap shiny part shifts ? Or the whole magnet assy, I can see how the magnet+pole would be heavier and over power its glue easier, but the main magnetic attraction forces are between the pole piece and the plate that's part of the woofers frame.
2. Then have you noticed that it shifts in one direction over another - The woofer is installed with the VC wires on top, so a shift would be in the direction of gravity - so away from the wires for the VC.
Thanks.
Srinath,
Now I have a couple questions about the magnet shift for people who have opened em.
1. Do you see that the pole piece - the outer cap shiny part shifts ? Or the whole magnet assy, I can see how the magnet+pole would be heavier and over power its glue easier, but the main magnetic attraction forces are between the pole piece and the plate that's part of the woofers frame.
2. Then have you noticed that it shifts in one direction over another - The woofer is installed with the VC wires on top, so a shift would be in the direction of gravity - so away from the wires for the VC.
Thanks.
Srinath,
edgewound
JBL Pro Authorized...
The correct way to realign the shifted magnet is to pry it apart and realign fresh. If the moving assembly is in good shape...voice coil still good, etc....
Carefully removed the dust cap by painting the glue joint with acetone. Use a suitable tool like a dull exacto knife to separate the glue joint. Be patient and use several applications of acetone. The Japanese glue is pretty hard and needs time to soften. Pick away the bits of rubber glue to clean it up for reuse.
Debond the cone and spider from the frame and remove the cone assembly. The voice coil is edgewound copper on a paper former. The surround is cloth, so let acetone do its work and carefully pry away the surround first, then the spider. It's a challenge of patience to get the spider off the frame landing without tearing it. Lots of acetone.
Remove the motor from the frame. Measure the diameter of the pole piece with a caliper around the copper sleeve. Measure the diameter of the top plate opening with a caliper, then subtract the pole piece diameter from the top plate hole diameter to get the difference. Divide the difference by 2 to get the gap width...~.068". You'll now need mylar shim material to realign the gap. Preferably a circular piece to fit around most of the pole piece diameter.
Clean ALL the epoxy and corrosion off the mating surface of the back plate, pole piece . EVERY LAST SPECK! Clean the mating surfaces of the magnet and back plate with acetone. Reattach the top plate to the frame. Reactivate the black rubber glue bond with acetone beforehand.
Here comes the fun part.
I like to use cyanoacrylate with an accelerator for the adhesive. This operation is best with a turntable like a sturdy wooden lazy Susan. Center the back plate, pole piece up, on the turntable and rotate while applying a continuous bead of adhesive from the inner diameter to the outer. Spray a mist of accelerator on magnet bonding surface. Lube both the pole piece surface of the gap and the top plate gap surface. Makes it easier to remove the shim.
Place the shim around the pole piece and lower the frame/top plate over the shim keeping your fingers out of the way...and WHAM! The back plate and magnet will forcefully attract and follow the shim for a nice realignment. Let the adhesive cure for several minutes before removing the shim, and you should be good to go to reinstall the cone assembly with a shim of about .007".
I just did this yesterday while my customer watched me disassemble his prized woofer. I reassembled later after he left. It's a win-win for all involved.
You need to be this thorough to make sure the bond is strong and doesn't happen again.
Carefully removed the dust cap by painting the glue joint with acetone. Use a suitable tool like a dull exacto knife to separate the glue joint. Be patient and use several applications of acetone. The Japanese glue is pretty hard and needs time to soften. Pick away the bits of rubber glue to clean it up for reuse.
Debond the cone and spider from the frame and remove the cone assembly. The voice coil is edgewound copper on a paper former. The surround is cloth, so let acetone do its work and carefully pry away the surround first, then the spider. It's a challenge of patience to get the spider off the frame landing without tearing it. Lots of acetone.
Remove the motor from the frame. Measure the diameter of the pole piece with a caliper around the copper sleeve. Measure the diameter of the top plate opening with a caliper, then subtract the pole piece diameter from the top plate hole diameter to get the difference. Divide the difference by 2 to get the gap width...~.068". You'll now need mylar shim material to realign the gap. Preferably a circular piece to fit around most of the pole piece diameter.
Clean ALL the epoxy and corrosion off the mating surface of the back plate, pole piece . EVERY LAST SPECK! Clean the mating surfaces of the magnet and back plate with acetone. Reattach the top plate to the frame. Reactivate the black rubber glue bond with acetone beforehand.
Here comes the fun part.
I like to use cyanoacrylate with an accelerator for the adhesive. This operation is best with a turntable like a sturdy wooden lazy Susan. Center the back plate, pole piece up, on the turntable and rotate while applying a continuous bead of adhesive from the inner diameter to the outer. Spray a mist of accelerator on magnet bonding surface. Lube both the pole piece surface of the gap and the top plate gap surface. Makes it easier to remove the shim.
Place the shim around the pole piece and lower the frame/top plate over the shim keeping your fingers out of the way...and WHAM! The back plate and magnet will forcefully attract and follow the shim for a nice realignment. Let the adhesive cure for several minutes before removing the shim, and you should be good to go to reinstall the cone assembly with a shim of about .007".
I just did this yesterday while my customer watched me disassemble his prized woofer. I reassembled later after he left. It's a win-win for all involved.
You need to be this thorough to make sure the bond is strong and doesn't happen again.