Dr.Gonzo
My transistors hurt
This might be covered elsewhere in the forum but if not maybe it will help someone. Back story - I picked up a pair of Boston acoustics a-60's that had been re-foamed, when I got home & tested them up one speaker had what I assumed was a v.coil rub. The guy didn't seem to know what he was doing, glue slathered everywhere & dust caps still intact so who knows if he bothered to center the coils properly. I removed the dust caps & shimmed the coils then glued another set of foams on, but the one woofer still made this weird chirping noise. Both woofers test the same ohms, no shorts on the meter & no audible noise when cycling the woofer by hand so I figured it must be a piece of debris in there or a loose coil. I didn't wanna ruin my brand new foams so I decided to remove the magnet. Now how to do that without wrecking anything.......... No flames, no hammers & chisels, no crowbars, just an old clothes iron.
I put the speaker on the bench, magnet up. Set the iron on max & once it got to temp I rest it flat on the magnet assembly for about 4-5 min. Pry/twist with 2 steak knives on either side & the rear plate/pole piece lifted right off, now use one of the knifes to clean the adhesive off the magnet surface so the iron makes full contact with the ceramic. Put the iron directly on the ceramic portion of the magnet for about 4-5 min then use a piece of hardwood to pry it up, if everything's hot enough then steady pressure on the wood should lift the magnet in about 5-10 sec. (This was my experience, your time/temp may vary). No part of the speaker was damaged during this experiment & Lo and behold there was the loose section of voice coil. There seems to be enough info about re-centering & glueing the magnet so I'll stop here. (p.s. the idea to use the clothes iron came from an old machinist trick to install a press fit bearing on a shaft, set your bearing on the hot iron for 10 min or so & it'll drop right on the shaft, the iron doesn't get got enough to damage the bearing just hot enough to expand it)
I put the speaker on the bench, magnet up. Set the iron on max & once it got to temp I rest it flat on the magnet assembly for about 4-5 min. Pry/twist with 2 steak knives on either side & the rear plate/pole piece lifted right off, now use one of the knifes to clean the adhesive off the magnet surface so the iron makes full contact with the ceramic. Put the iron directly on the ceramic portion of the magnet for about 4-5 min then use a piece of hardwood to pry it up, if everything's hot enough then steady pressure on the wood should lift the magnet in about 5-10 sec. (This was my experience, your time/temp may vary). No part of the speaker was damaged during this experiment & Lo and behold there was the loose section of voice coil. There seems to be enough info about re-centering & glueing the magnet so I'll stop here. (p.s. the idea to use the clothes iron came from an old machinist trick to install a press fit bearing on a shaft, set your bearing on the hot iron for 10 min or so & it'll drop right on the shaft, the iron doesn't get got enough to damage the bearing just hot enough to expand it)