1955 Granco FM-610U Tube Radio (pics)

[dieseljeep]

Originally Posted by Reece

I have fixed plenty of speakers with the water trick. Get some water in a cup. Using your finger or a small brush, dampen the whole cone. Keep water out of the voice coil area. Set the radio with the cone facing UP towards the ceiling and let dry overnight. Be sure it's completely dry and try it the next day. You have nothing to lose.

I'm going to try that trick! I have a Zenith 845 series, with the 8" bass and midrange speaker. The voice coil has a real slight drag, only heard at low volume.
I think it should be allowed to air dry and not force dried, as by a hair dryer or such.

[Robb]

Im going to try this.

thanks

[Reece]

Yes, let it dry slowly, overnight and into the next day, even. What happens is that over the years the cone sags by gravity and by absorbing moisture. When it's dampened again, it becomes pliable, and the spider, which is not made of paper but of a treated cloth, and is not hydroscopic, can now pull the cone back into center where it will stay when the paper dries out again.

If this doesn't work, the next step is to remove any felt center cover disk, loosen the glue joint between the outer edge of the spider and the speaker frame with acetone, and use three or four thin paper or business card spacers between the voice coil and the center pole piece. Then the spider is reglued to the speaker frame.

Should have said at the first, you can tell if it's a voice coil rub, with radio off gently grasp cone 180 degrees apart with finger and thumb and move slightly in and out: listen for scratching to indicate a rubbing voice coil which should respond to the wet cone treatment.