FOLLOW THE RESTORATION: brass Edison Needle Type reproducer
Posted: Sat Nov 12, 2016 3:34 pm
Much like the Victrola #2 reproducer, the Edison Needle Type (NTP) reproducer is VERY VERY VERY under-rated, primarily because it is often repaired incorrectly. This specific reproducer would not only make a perfect replacement on the Needle Type Portable (NTP), P1 or P2 portable, but alone by itself it is very Art Deco. The reproducer is VERY well made, with lots of plates and screws, and gasketry. The one part which everyone misses when repairing is the mounting flange....which was originally very soft latex rubber. It isolates the vibration of the reproducer from the tone arm, and also eliminates reflexive feedback to the needle which increases record wear and strident tones. These NTP reproducers are absolute monsters of sound.
This reproducer had an enlarged hole in the center of the diaphragm, so I cut a small piece of duralumin, formed it to the curve of the diaphragm cup, and bonded it into position with a very strong but lightweight adhesive (cyanoacrylate), a permanent repair. The needle bar is bearing suspended, much like a Viva Tonal, with ball bearings on cone screws. The allloy diaphragm is suspended with soft rubber (now butyl rubber) gaskets. Whenever I install gaskets, I install with GENTLE clamping pressure, to allow for a good seal, but to also allow the diaphragm to move with low frequencies. TOO MUCH PRESSURE STRANGLES THE ABILITY FOR THE DIAPHRAGM TO WORK.
The mounting flange gasket, I have replaced with silicone (GE Silicone II). In the excitement of the work, I failed to take a picture of the application of silicone. I spread two circular paths onto the back plate. One around the center hole, and another midway between the center hole and the outer edge. I then sandwiched it together, using three pieces of card stock as a spacer to allow a proper gap to keep the vibrations isolated. After the silicone cures, we will have a perfect isolator!
The three shoulder screws that hold the back flange onto the body also had rubber washers and insulators...all which have turned rock hard from age. I cut some surgical latex tubing for each screw to isolate them from the flange. Tonight the silicone will cure. Tomorrow I'll remove the cardstock shims.
And that's how it's done!
This reproducer had an enlarged hole in the center of the diaphragm, so I cut a small piece of duralumin, formed it to the curve of the diaphragm cup, and bonded it into position with a very strong but lightweight adhesive (cyanoacrylate), a permanent repair. The needle bar is bearing suspended, much like a Viva Tonal, with ball bearings on cone screws. The allloy diaphragm is suspended with soft rubber (now butyl rubber) gaskets. Whenever I install gaskets, I install with GENTLE clamping pressure, to allow for a good seal, but to also allow the diaphragm to move with low frequencies. TOO MUCH PRESSURE STRANGLES THE ABILITY FOR THE DIAPHRAGM TO WORK.
The mounting flange gasket, I have replaced with silicone (GE Silicone II). In the excitement of the work, I failed to take a picture of the application of silicone. I spread two circular paths onto the back plate. One around the center hole, and another midway between the center hole and the outer edge. I then sandwiched it together, using three pieces of card stock as a spacer to allow a proper gap to keep the vibrations isolated. After the silicone cures, we will have a perfect isolator!
The three shoulder screws that hold the back flange onto the body also had rubber washers and insulators...all which have turned rock hard from age. I cut some surgical latex tubing for each screw to isolate them from the flange. Tonight the silicone will cure. Tomorrow I'll remove the cardstock shims.
And that's how it's done!