ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Had these delivered today.......usual story, cones held fast by a wandering magnet against the voice coil, otherwise look in good shape
seen from the side elevation the problem is apparent........we see this all the time.
Once the magnets have been popped off the frame both voice coils are nice and free, I will check out the resistance of the coils to be sure but they look very recoverable.
Will clean everything up and get them epoxyed back into place.......
Hi Criag
Are these from a pair of S45.2?
I'm about to inherit a pair of these and want to carry out some preventative maintenance on them to avoid this happening, so am very interested in your post!
Cheers
Nigel
Apply epoxy resin all around the magnet top and bottom as shown, this wont stop the core becoming free however but I suspect that only happens when the magnet moves and dislodges the core....so if the magnet is fixed firmly the odds are in your favour.
Craig
Brilliant! And there was me dreading a complete strip down and re-assembly (I'm a bit ham-fisted), but I think even I can carry out your very sensible advice!
And thanks for replying so quickly!
Nice job Craig!
Magnets cleaned up and epoxy applied prior to placing back onto the frame, the only thing to watch for is putting them back the same way around as they came out, the magnets are polarised after all. Cores back onto the back plates after a clean up and also epoxy glued into place.....24hrs to set.
Looking good, did the coils check out OK?
Keith
Coils both measured around 3.4 ohms.........good readings
Girlfriends hairdryer to soften the glue and peel back the dust covers to see whats going on....
Clamp the base plate, complete with newly affixed magnet core, in the vice and set it a little below the level of the jaws.....3-4mm or so.
And very carefully lower the speaker onto the core, watching closely through the hole created by removing the dustcap, untill the magnet pulls down onto the vice jaws
Releasing the vice grip allows the base plate to snap up against the magnet once the core is safely inside the voice coil therefore reducing the risk of damaging the coil on reassembly
Fit the "alignment tool" and centre the core.........
This takes around 5mins............
Pour in the epoxy and leave to rest overnight......
Soon be ready for the big test.
Second speaker into the pot....quite literally! doing this allows the epoxy to go off without the weight of the speaker pressing on the rubber surround and pushing the voice coil into the core. Just a precaution really.
Now where really cooking.
Epoxy in the gaps where the adjustment screws where located, with epoxy all around it should be good for another 40yrs.
Fascinating procedure. The gap you left on the step where you used the vice...Was that for some insurance so you have a bit of control on the initial placement? It seems like the first lowering of the speaker onto the core would be a tense moment. Once in place you adjust the screws on your alignment tool to center the core?
Well done on the procedure and thanks for sharing the pictures. What kind of epoxy do you use?
-sonavor
Sonavor..
Yes the gap between the base plate and the magnet, when the base plate is held in the vice, allows you to carefully place the voice coil over the core holding the speaker tightly in both hands, the magnet will jump the last few millimeters as you lower the assembly over the core but its a lot easier to control this way. And as you say the initial lowering is the most fraught part of the procedure, I dont attempt to centre the core until the vice grip is released of course. For the epoxy I have tried both Araldite and Gorilla glue versions....both seem to harden off fine in a 24hr window.
Tested these out with one of my cabinets connected to a BM6000.........
And the other one........these sound as good as new, I will get these wrapped up and in the post in the next day or so.
Many thanks for taking the time to repair them. And looking forward to putting back together with my BM4400.
Please PM with your bank details and expenditures.
Kind regards
Top job Craig, congrats to both of you
Collecting Vintage B&O is not a hobby, its a lifestyle.
My pleasure Keith.....I will get them out to you as soon as I can, its tricky through the week due to work commitments but I'll see if the girlfriend can take them down to the post office tomorrow......as for my expenses the addition of a bottle of New Zealand Sauvignon Blanc is always welcome in our house ;¬)
All boxed up and ready to go.....girlfriend has offered to take them down to the post office tomorrow, next day delivery signed for.
Thanks Craig
As soon as you know the final cost PM and I’ll add a bit extra for a couple of bottles for you and your girlfriend.
Your a grand chap!
sent you an email with the tracking number.....on there way!
The woofers arrived today, fitted and Sound Fantastic.
Many thanks again Craig for taking the time to repair them.
Its my pleasure Keith.............
Without pics it didn't happen
Cheers Soren