[dconant]

Hello,

I have a 1937 or so Philco speaker that looks to have a waxy build up around the voice coil. This sometimes prevents the speaker cone from its full travel. If I push on the cone near the spider several times it will free up but if its sets for a couple of days it sticks again. I was wondering if I could clean that crud away. If so what would be best? Picture is not the best but shows the area I am speaking about.

Thank you,
Dan

[Radioroslyn]

Well you could use a drift the drive the 4 fasteners out. Then you can lift the field coil assembly off of the basket. You'll probably will want to unsolder the voice coil and fc wires. Pull it straight up else you'll reck the vc as it's fitted down in the gap. The tough part is getting the fasteners back in. I would use a c clamp and socket to apply pressure to the head of it to press it back in place. Think about what you are doing before you do it... Be sure to keep the fc in place till your really to remove it. You don't want it bouncing around as it could deform or rip the vc out of the cone.

Once you get it apart you can clean the gap which probably full of dirt and dust with thin piece of plastic.

GL

[dconant]

Wow that sounds like pretty rough treatment for a speaker. I'll have t think about that. Thanks GL.

[Chas]

Before I would tear the speaker down, I would try using a soak in odorless mineral spirits, (odorless has less aromatic solvent). The purpose is to dissolve the wax that has melted from the field coil into the voice coil gap. Mineral spirits will not dissolve the collodion glue that holds the voice coil winding nor loosen the cone to voice coil former bonding. Use an acid brush to flow more mineral spirits

May, want to remove the center spider, first, to do that will need acetone and those long disposable eyedroppers. Use the eyedropper to flow acetone sparingly into the bond of the spider to the voice coil. Repeat maybe several times over 10 minutes, that, should soften the collodion and allow careful removal of the spider. Treasure the spider as no one is making these. Though some have created via 3D printing... Gently flexing the cone while mineral spirit/brush cleaning.

Create shims, three from scrap plastic bottles or cans that can fit between the leaves of the spider. must use three and not very wide, shim equally until it is noticed that the shims are supporting the voice coil and not allowing movement. Place the spider over the shims and down to the apex of the cone. Be sure the hole in the spider is centered over the screw hole in the pole piece. Apply G-C speaker service cement using the eyedropper as a bead around the bond line of the cone/spider. Allow an hour at least for a setup or 6 hours for a hard set, run the screw in the spider and secure to pole piece. Pull shims. Speaker should now be clear of debris and cone centered.

If the procedure fails then knocking apart the speaker is the other option. The frame can be tapped to receive grade 5 screws to re-assemble. The pole piece should be shimmed at the time the magnet yoke is re-installed to keep the pole piece centered.

Grade 5, as one has to really sock down the yoke...


BTW, the wax melted and flowed because of high current load, probably a defective filter cap and/or low bias on PA tube, check...

GL

Chas

[dconant]

Thanks for the detailed solution Chas. Not so sure I will be able to do that but I may try. The radio has been completely recapped. I do have a spare speaker that I might use instead of messing with the original one. 

Dan

[Chas]

Dan,

I forgot to add a warning, mineral spirits are hazardous, use in an open area as well as acetone. Wear nitrile gloves but these will give way with acetone. Beware of fumes creeping to a source of ignition, like the hot water heater of the oven pilot.

Keep the solvents off the skin, all the times...

BTW my hot water heater gave out some 10 days ago, I got some 20 years out of it but what happens the firebox draws in solvent fumes. It does not explode but the flame converts solvent fumes to acids that eat the bottom of the tank

There are a lot of details I had to work out with common tools to repair speakers. One has to apply some two steps ahead to work out how to accomplish the task of speaker repair.

IMHO the original speaker will always sound the best, though some may argue the "hard" cones of the early Philcos rather tinny. There is good reason. Lower tones from a new speaker will cause more vibration to tube elements and possible mechanical oscillations... The other benefit is the ideal filtering of the field coil as a choke.

GL

Chas

[dconant]

Thanks for the warning, never realized that about mineral spirits. My replacement speaker is a field coil Philco speaker.

Dan

[Chas]

Dan,

I was unaware of common solvent reaction to fire, that is beyond explosion... Though I did know that fluorocarbons, Freon, break down.

Until I read the instructions for the new water heater, a high efficiency 30 gal. Rheem. Even common solvents, laundry product fumes (esp chlorine bleach), though may not burn are broken down in the flames to acids that condense on the bottom and flue of the hot water heater, to a lesser extent also erode the vent piping as well.

Another forgotten example is the propellant in some aerosol cans.

I had an experience when I was fitting rolled rubber foam insulation around a refrigeration line in the utility room. I used a can of silicone spray to ease the rubber into the wall. The hot water heater started and roasted the fumes of the Freon which I did not smell, into phosgene gas. I felt the tingle in my nose, I shut the gas main, had my family run out of the house. I went in 15 minutes later and ventilated the utility room. The fumes turned all the copper pipes down to 4' off the floor green. Very scary, needless to say the hot water heater was short lived

My apologies for going off topic, but solvent fumes are a danger beyond the explosion risk.

My "shop" is a made-over garage, I open the back door and slider at opposite ends of the room to ventilate when using solvents.

Chas

[dconant]

Chas,

Wow. I guess you never know. My shop is in the basement away from furnace and hot water heater separated by two doors. I have used brake cleaner (non flammable) but just a small squirt. 

Is it possible to make a new spider if needed out of something like thick card stock? I saw Buzz1151 (YouTube video) make one but I don't remember what he used.

Dan