Mica Replacement tips

[Henry]

When my Exhibition was rebuilt, the original mica was retained. I subsequently reworked the box myself because, in the rebuild, the mica gaskets were pinched. This job involved removal of the mica and rewaxing the needle bar. On the old forum there was a discussion of the different types of beeswax, and one of the knowledgeable posters recommended brown beeswax as the best for the job. I happened to have some of the stuff on hand, but I've seen it for sale by vendors who sell beeswax candles. When I flowed the wax on (using a 25 watt pencil-tip soldering iron) it made a nice circular deposit about 5/16ths-inch diameter, and wax also flowed through the tiny hole around the tiny screw and onto the back of the mica. The sound box plays beautifully: no distortion or rattling. The keys to a successful rebuild, IMO, are these: soft, pliable front gaskets; new back flange, sealed against air leaks; mica diaphragm in A-1 condition; proper adjustment of the needle bar relative to the face of the diaphragm; a good "wax job," as described; and some good luck! The results will justify your efforts.

[Technomaniac]

I currently have one acting similarly, but it seems to me that my mica is too thick and unweilding, so that all of the wave motion occurs between the needle and the mica. , the mica becoming a fixed node. Ive been looking for thinner mica.

[Lah Ca]

I recently rebuilt two Aeolian Vocalion reproducers. The rebuilds were my first and so far only two. I did my spare soundbox first in case I damaged something. Then I did the original.

viewtopic.php?f=7&t=55990&sid=d5db0fb7c ... 731362cc1f

Various people here gave me advice. Member Inigo's advice--go slowly and carefully--helped me through my initial nervousness.

I got mica and gasket tubing from The Phonograph Shop. The order was processed and shipped quickly. Via email they were helpful if hurried and brief.

What can I tell you that might help you?

If you go slowly and carefully, the job is not very difficult. It just requires close attention and some manual dexterity. The results should be startling. Even my non-audiophile and somewhat musically inattentive wife was gobsmacked at the positive difference the rebuilt reproducer made to her enjoyment of her favourite records.

Watch as many video tutorials as you can find for rebuilds of similar reproducers.

In disassembling the reproducer do not force anything. Be patient. On both of my AV soundboxes, I had to apply a drop of penetrating oil on the end of a toothpick to most screws. I had to leave things for a day or two and then come back and apply more oil and wait again, before the screws would come out easily. Don't force things. Be patient.

Be careful when detaching the needle bar from the mica. Parts are very small here. On one of my reproducers there were two tiny extremely thin washers, one on either side of the mica, barely visible through the old brown wax. The reproducer with the washers sounds much better than the one without.

Don't forget to clean, adjust, and re-lubricate the needle bar on its pivot pins. I gave mine a bath in isopropyl alcohol while working the needle bar back and forth. A century of black gunk came loose and was flushed out. In the absence of other advice and with the thought that grease will have a greater dampening effect on mechanical chatter than oil, I applied tiny amounts of synthetic grease on the end of a toothpick to the pivot points and worked the needle bar back and forth to spread the grease around. As explained by helpful members here, the screw-pivot pins should be as tight as possible to restrict chatter caused by movement against the axis of the pins but without restricting movement on the axis. Also check that needle bar is centred between the pins--it does not have to be OCD machinist thousands of an inch exact, but if it is out of centre much it will cause problems getting the mica aligned (the mica should not contact the metal of the sound box when it is in place--it should rest on the gasket with a fairly even gap all around between it and the metal housing of the soundbox). I also cleaned and re-lubricated the thumbscrew workings for the needle chuck--these were also gunked up with black grunge and stiff to the point of being troublesome. I used a tiny drop of synthetic oil here after cleaning.

Two points of uncertainty for a novice re-builder (read me) are cutting gasket tubing and applying wax.

If uncertain about what length to cut the tubing to, err on the side of excess. The cut tubing can always be shortened but not lengthened. Use a very sharp utility knife. Cut as close as you can get to right angle to the tubing. Don't worry too much if there seems to be a tiny, tiny gap between the ends of the tubing when fitted into the reproducer. The compression on the tubing when the reproducer is reassembled seems to both flatten and extend the tubing. The gap will disappear if it is not too large.

With wax err on the side of caution. I know from sad experience it is very easy to use way, way too much, and then there is a cleanup job. Bee's wax can be worked into a soft putty-like consistency. Take a small piece, put it on something like a plate, squash it flat with the back of a finger nail, scrape it off, ball it up, and repeat until you have a very soft consistency. The small piece you then put on the end of the needle bar before heating can be pressed lightly into place, and it will stay there and not fall out of place while you nervously and tentatively fumble with the soldering iron on your first rebuild .

I could not find new back flange gaskets. AV machines are not as mainstream as other brands. So I used a rubber cleaning/rejuvenating solution, the stuff used for cassette player pinch rollers or laser printer rollers, and my century old gaskets came up fairly clean and pliable if still somewhat squashed.

[Inigo]

NIce explanation!

[PeteLeoni]

I would like to add that I found that too *little wax* causes a resonate peak around 1200 hz in the #2 reproducers. I found that out by adding a smaller and smaller ball of putty at the crook of the needle bar till the peak was diminished without damping out the high end. Eventually I realized that too little wax was the was the true issue and the guys at Victor knew a thing or two about horns, drivers and mass loading even before the input of the Western Electric geniuses and the illustrious Orthophonic.