Forum member MW magnet repair tool set

pitdogg2

Gardenstater wrote: »

Back in April March he said he had some problems and was sorry and would be sending it on in a week or two. Since then silence.

Time to drive over....

Gardenstater

He has had it for around 15 months.

msg

Man, you guys are rough. Everyone knows it takes 16 months.

Gardenstater

msg wrote: »

Man, you guys are rough. Everyone knows it takes 16 months.

Maybe you are right. It is only 12.5% (1/8 th) of a DECADE. Not really that long in that context.

plastic_avatar

A blink of your eye in geologic time.

Maybe I missed a message [goes to look].

Nothing in my inbox.

Tony M

I hope the guy gets it back to you but it seems he might be in jail, prison or he had to bail from where he was living and left it.

There's NOTHING else it can be used for and anybody finding it and doesn't know a thing about it or why he came into having it will never understand its purpose. It probably will forever be a mystery what happened to him and it.

SAD! UNLESS....

I really! enjoyed fixing a few woofers and will always be grateful for the opportunity to have had a chance to borrow it. It's a beautiful work of art and your machining skills are second to none. I actually had fun using it and saving those woofers from the trash bin.

xschop

Loaner jig #2 being sent out Monday to @MrGeology

MrGeology

Picked up three 6500's. All are seized but ohm out good. Will see how it goes.

MrGeology

A quick update.
Received the jig Friday (thanks @xschop ). After figuring out how to use it properly began using it on the three drivers Saturday.
These drivers are all new to me as of last month. You can see the considerable mag shift on each.
Driver#1 = MW6500 dated 02/81

Driver#2 = MW6500 dated 05/81

Driver#3 = MW6500 dated 11/79 (silver basket)

After considerable toying with how to use the jig, the first driver was easy to set. However while removing it form the jig heard a very quiet 'creak---snap!' and sure enough it had re-seized. Re-set it using the jig again and played some bass oriented music through it (hooked to an old crossover I had laying around) and after about 15 minutes decided to more gently remove from jig.
This time it was good for about 30 seconds just sitting on the work bench, but as I was looking for the glue heard that same quiet 'creak---snap!'. Checked and sure enough it had seized again.
Went through this about half a dozen times late Saturday evening, noticing that each time it lasted a little longer before re-seizing.
Decided to re-set, and leave in jig for 24 hours playing some bass oriented music at about 45W.
Came back Monday, released from jig, cleaned and glued with no problems.

Driver #2 will not set properly (suspect pole piece/VC not plumb).
Driver #3 was set in about 10 minutes, what a breeze. However it did the same thing as driver #1, would not stay set.
This time let sit in jig playing music from late Monday evening until early this morning (about 9 hours). It is now glued, curing and has not budged.

Glue is Loctite Power Grab Ultimate Clear and looks pretty much the same around the perimeter on both finished drivers.

Now looking into making a sleeve for the jig so can remove PP/Magnet from driver #2.

xschop

If it is shifted, you can pull the magnet off by hand.

txcoastal1

Look man if a caveman can do it

https://www.publicdomainpictures.net/pictures/170000/nahled/cave-man-chiseling.jpg

Gardenstater

You could stuff some soft stuff through the windows propping up the cone so the voice coil is out of harms way too. Wrap some Armacell around a couple wood dowels?

xschop

^^^I used Dacron on a couple of 6500's that I clearanced Base Plate ID's without removing the dust cap.^^^

xschop

txcoastal1 wrote: »

Look man if a caveman can do it

https://www.publicdomainpictures.net/pictures/170000/nahled/cave-man-chiseling.jpg

https://youtu.be/T_wS0Kw6k9c

MrGeology

Magnet came off so easy by hand.
First thing visible was some corrosion that was rubbing VC/baseplate. After cleaning it discovered the real problem was the VC coming through at an angle similar to @Gardenstater 's. No mater how you push the cone, the coil would rub (at about 120 degrees clockwise from the corrosion in the pic).

So took @xschop 's advise and Dremeled the baseplate ID out to 1.086"

And voila! no more coil rub.

And because the original glue made a mockery of trying to remove it with acetone.

Only problem is that its so slippery now you can move the magnet around between the two plates by hand. Simple to align, but having trouble with keeping alignment when releasing set screws. Currently aligned in jig now, will get back to it later today.

ratpin

Are you still sending these out? As far as post count, I was previously username "G-force" on the forum before losing my email and having to start a new account. Join date 2006.

xschop

Great job and driver save. You can clearly see from the pic how bad that one was off-axis. That'd be the only resolution short of file 13 with these drivers doing their corrosion process over time. Seen quite a few with this issue.
BLUE Loctite the PP to magnet first using alignment dowel to confirm concentricity of the two. After they set, reset them to the base plate in the jig with Blue Loc-Tite also.

No need to glue perimeters unless youre OCD.

pitdogg2

Why would you not use red (271 or 262) to permanently glue the magnet?

MrGeology

xschop wrote: »

Great job and driver save. You can clearly see from the pic how bad that one was off-axis. That'd be the only resolution short of file 13 with these drivers doing their corrosion process over time. Seen quite a few with this issue.
BLUE Loctite the PP to magnet first using alignment dowel to confirm concentricity of the two. After they set, reset them to the base plate in the jig with Blue Loc-Tite also.

No need to glue perimeters unless youre OCD.

Loctite 243 or is 242 OK? Haven't got any 243 and haven't seen it locally. One of the industrial supply shops may have it, but that takes a bit of running around to check.

xschop

Blue 242 is what I use.
The red 271 does not give much work time.

MrGeology

Never mind, Loctite 243 available at local Napa...

MrGeology

Ran into a small problem with the centering tool. The hole in the end fits the PP to perfection. However it won't fit through this particular magnet.
Micrometer read 1.2735" in one orientation and 1.270" in the other. Too hard to hold calipers on magnet and operate camera, so modified a piece of sched 40 PVC (3/4" flange) that was laying around to verify fitment. I forget what the centering tool measures.



Figured @xschop may be interested in these numbers for future reference.

Gardenstater

Yeah it doesn't fit the MW6500s in my experience as well. I was going to make one out of PVC on my lathe but haven't gotten to it yet.

xschop

I spun the dowel off the CNC program from previous batch.

If one of you guys want to chuck it on a manual lathe and index it to the 6500 ID @ 0.200 depth, then the dowel would center 6500's and newer drivers as well.

Hind sight is still 20/20

Gardenstater

@Kryten could you do this ^^ to yours as well? 🤣😜

xschop

It was everybody's here on the forum, now it belongs to somebody in Manasshat, VA.

MrGeology

On Saturday I managed to negotiate a deal for a pair of M5jr (circa May 1989). The drivers are pristine and did not need reset via the jig so they are now glued. They feel like they aren't even broken in yet.

MrGeology

Just got back from a rather long road trip which yielded a pair of M5B's (I believe) with the 8" passive, MW6502 and SL2000's, circa 1985.
Massive corrosion (?) has this 6502 locked up for the most part. Pics of it, as well as an update on the MW6500 driver #2 upcoming, once I have caught up on some sleep...

xschop

Good score. 5Bs respond well to all the mods, don't require much power for amplification, and fill any space with big sound stage.

MrGeology

As far as MW6500 driver #2 goes, not sure it is salvageable after all. Actually wondering if something went wrong from the factory after closer inspection.
-Before I pulled it apart (the first time) had it freed up and played music through it to see if that would help VC rub (it didn't). While doing this noted that it sounded a few db quieter than the other two 6500's on the bench and hoped it was just due to VC rub.
Turns out it was not. DATS confirms after re-assembly it measures a few db lower than any other 6500's I own (six drivers in total).
The impedance chart looks all wrong too.
The VC also measures 40% less induction (Le) than any other 6500's I have (0.3 mH vs the usual 0.5+ mH). It also measures 6.3 ohms.
Luckily Blue Loctite was used on re-assembly. So used a heat gun on magnet and plates while rotating on a lazy Susan. Kept an eye on temps with an IR thermometer. Once it was above 250 degrees, set the jig back on and used it to break the plates loose from the magnet. So easy. Re-centered then let cool and pulled magnet off by hand again.

The plates mic out at 0.250" and the magnet mics out at 0.545".

-The first time it was apart noticed that the VC former was curled over (to the inside) on the end under the dust cover, so gently (as possible) straightened it out.
After second disassembly cut the dust cover off to inspect. The VC former protrudes 0.100" from cone (not sure what it should be).
You can see where the former had to be straightened. Also not sure if the cone is supposed to look like that around where it is attached to the former. (Pics of others on the forum do not look like this)

Upon further inspection, the spider has a convex shape (instead of flat or concave like the other drivers) when in resting position. The other drivers also have noticeably more cone length at the base where the spider is glued to the former than this one.

Not sure where the resting VC position should be, but it measures 0.170" recess from baseplate.

Contemplating doing a Wu-coil overhaul on this since there is nothing to loose.
In the meantime moving on to the 5B MW repair.