by Joe_DS »
Mon Jan 26, 2015 5:15 am
I've never worked on a Sonora sound box, but, based on the photos--
and assuming nothing is missing, and the back plate doesn't simply screw in from the back--it looks like the back plate would have to be inserted through the large front opening--once the needle bar is removed. If that's the case, then there should be a groove or notch that will secure it in place in the proper position.
After that, you'd install the "back" rubber tube gasket first, then the diaphragm (which should have just enough clearance to fit through the front opening), and then the "front" gasket which would be tucked between the rim of the front plate and the edge of the diaphragm.
Following this, you would re-attach the needle bar to the fulcrum, and turn the screws on either side of the fulcrum so that the "foot" of the needle bar just touches the center hole of the diaphragm. Then, re-attach the small foot to the center of the diaphragm with the tiny screw. The job would be completed by putting a tiny bead of wax over the foot and holding a match over it until it melts to create an air-tight seal.
After this is done, you would test the sound box. If it's shrill sounding or if it rattles, you would adjust one or both fulcrum screws until it sounds right to you.
If the back plate does not "lock" in place when inserting it through the front, you'll probably want to get in touch with one of the shops that specialize in sound box repair, such as Great Lakes Antique Phonograph Company --
http://www.victroladoctor.com/HTH,
Joe