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
This was delivered in the post today, usual issue.....cone seized solid in the coil.
Otherwise its in very good shape, coil measures up at 3.4 ohms, cone and rubber both in good condition, one can see that the issue is the magnet has shifted on the frame...been knocked I expect....doesn't show well in the picture but it is off to one side.
Clamped it in the vice and popped it apart, for me the most scary part of the exercise, once its separated out each part can be rubbed down and the old adhesive removed.
The magnet and its mating face on the frame cleaned up first prior to allying epoxy, need to be careful to put the magnet back in the same polarity.
This doesn't need to be dead centre on the frame, but the closer it is the better.....
The rear plate and core need to be cleaned up too, old adhesive removed....
And then they need epoxying together.....they need to be placed on a completely flat surface or the core floats around!
Ooooh... glad someone knowledgeable is doing this :-D
thanks for updates craig
And for quick progress!
frugal audiophile
Dust cap lifted off with the assistance of the girlfriends hairdryer...….
When the epoxy has cured the base plate is held in a vice and the frame, magnet and coil are carefully lowered onto the upright core. then the "alignment jig" is fitted, a saucepan is useful to rest everything on
Adjusting the screws around the lower half of the jig secures it to the magnet, then looking through the dustcap one can adjust the upper row of screws to centre the core in the coil.....
This takes very little time and once happy epoxy is applied before opening a bottle of wine...….
great work!
Any recommendation on wine for this repair :-)
Will be on the look for some stands for these I think... might have to make some since they are reasonably rare I think...
No one can do this better than you Craig!
Now looking at how the old glue was applied; it tells a lot why the magnet shifted...
Keep filling the Workbench forum with exiting projects Craig!
I have been listening to the speakers for a couple weeks now occasionally, seems no issues with them at all really.
I may now take some measures to stiffen the enclosures and recap, and check the resistors haven't caused heat damage.
and in background I now have to consider making some stands myself since these are so rare now.
I want to lift them 18in / 45cm from the ground over a low sideboard which I think is not possible with the original stands.
the low bass seems present but modern music with very low frequencies seems to be confused.
bass guitar and drums seem well reproduced though.
classical music really protrays well.
I think high treble could be improved with cap change, is there a kit for caps / resistors?
also the sockets for the speaker wires at the back are giving really quite a loose connection, I've not seen any common solution for this yet, can anyone help?
and thanks again to Craig...
Beo_Jean: No one can do this better than you Craig! Now looking at how the old glue was applied; it tells a lot why the magnet shifted... Keep filling the Workbench forum with exiting projects Craig!
Charles
Thats very kind of you to say....I am keeping an eye open for another BG4000 in need of repair, friend of mine is quite taken with mine (and withb good reason )
Craig: This was delivered in the post today, usual issue.....cone seized solid in the coil.
Just received a pair of these and one of the bass units have suffered the same fate. Reading 3.4 ohms across the coil so I'm hoping it can be fixed? I've read several threads here on the topic, which leads me to this question? Am i right in thinking it's just the strength of the magnet holding the motor system together? Hence you have to prise them apart? Cheers.
The magnet, core that sits inside and the top plate are all glued together during manufacture.....the glue gets tired over the years and fails, follow the post and carefully pull the magnet from the frame.....
I have a pair extra. Let me know if you're interested.
styppen: I have a pair extra. Let me know if you're interested.
What are you asking for them?
Craig: The magnet, core that sits inside and the top plate are all glued together during manufacture.....the glue gets tired over the years and fails, follow the post and carefully pull the magnet from the frame.....
Thanks Craig I had a little play over the weekend and managed to separate everything. Will be cleaning them up today and re-gluing following your thread. Without a Jig I'm racking my brain how to align the centre cone accurately.
I have tried a couple of different methods....none have worked as well as the jig method, its not difficult to make one from a section of plastic pipe ;¬) I can post a few pics if you like?
Craig