request a picture of a Victor Orthophonic phase plug

[A Ford 1]

Hi All,
I was just talking to a phonograph collector, re-builder here in Baltimore and he spoke of a phase plug in later Orthophonic reproducers. I would like to see an example of one of these phase plugs. I am in hopes that some one in the group would be kind enough to send in a few photos of same. If some one has a phase plug they are willing to sell I would be interested to buy it just to see one and I would also like to know any information on how they are installed. Thank you all for any information,
Allen

[Edisone]

I believe it's held by screws, so it might be unwise to try adding one to a pot-metal OSB.

[De Soto Frank]

As far I have seen, among Orthophonic reproducers, the cone-shaped "phase plug" was used on the early pot-metal versions, later ones have a silver-colored stamped sheet-metal "spider" ( flat, three-legs ) that I think is there to prevent curious fingers from touching / damaging the diaphragm.

The flat spider is held in place by the rubber mounting bushing.

The cone-shaped phase-plug is secured to the inside of the back plate with three machine screws.

The pot-metal phase plug is also susceptible to cracking / flaking / crumbling.


I do not think I would try to add one to an OSB that did not originally have one... trying to drill and tap those tiny screw-holes in that unstable pot-metal is probably a risky adventure.

Will see if I can take some pictures tomorrow.

[Uncle Vanya]

As far I have seen, among Orthophonic reproducers, the cone-shaped "phase plug" was used on the early pot-metal versions, later ones have a silver-colored stamped sheet-metal "spider" ( flat, three-legs ) that I think is there to prevent curious fingers from touching / damaging the diaphragm.

The flat spider is held in place by the rubber mounting bushing.

The cone-shaped phase-plug is secured to the inside of the back plate with three machine screws.

The pot-metal phase plug is also susceptible to cracking / flaking / crumbling.


I do not think I would try to add one to an OSB that did not originally have one... trying to drill and tap those tiny screw-holes in that unstable pot-metal is probably a risky adventure.

Will see if I can take some pictures tomorrow.

The earliest brass reproducers had an open back, similar to the old mica diaphragm units. This left the fragile duralumin diaphragm open to damage, and so sometime in early 1926 a little guard made of stamped nickels brass was added. Then late in 1926 the phasing plug was added. All remaining Victor Orthophonic No. 5 reproducers were fitted with this refinement. In 1931 RCA Victor made another run of sound boxes, for bot replacement use in zorthophonic Victrolas and for new portables. These late sound boxes had a three armed guard, similar in shape to the early brass guard, cast right into the back plate of the reproducer. The phasing plug is later than the nickeled brass guard.

Now, as for adding a phasing plug, well the back plates differed. There were no bosses for the screws to hold the plug on the earlier reproducers, and the shape of the sound chamber differed, also. If you want a phasing plug in your reproducer, hunt up a unit that is fitted with one.

[A Ford 1]

I thank each of you for your input and am looking forward to the photos. I have two thoughts in mind one is to duplicate, may be by 3D printing or other methods, a plug using an original as a model to install in my brass Orthophonic in my Radiola-Borgia II in a way that is reversible and to use a good condition old diaphragm in a reproduction case(RC) for the 78 rpm or lateral adapter for my C-19 DD. If I purchase an old reproducer that can be restored without the need of a (RC) then of course I would take advantage of not needing to buy a (RC). But truth be know I am not sure yet exactly what I am going to do as all is still in the thought phase.
Thank you all most kindly and continue any input you have,
Allen

[Edisone]

I might have an "exploded" OSB someplace; I'll look when I get home. Can't recall if it has a plug, but most likely it has. Actually, if the parts fit, you could probably use burnt shellac to hold them together - it certainly wouldn't hurt to try.

[phonojim]

Here are some pictures for you. The first picture shows the three types of Orthophonic backs. Upper left is the first type back which never had a phase plug. Upper right is the commonly found type with the cast plug held in place with 3 screws. The bottom one is a third type in which the plug is an integral part of the casting. I don't know where this one fits in chronologically. It may be the second type, as it would have been relatively easy to add the cast crossbars to the first type. The second picture shows a back with the plug removed and the third shows the plug itself. As you can see, it would be rather difficult to add a phase plug to an Orthophonic which did not come equipped with one, although it could be done. Making a phase plug would be a more difficult process than it might seem. It is a much more complicated shape than it appears at first glance. That said, it would be easier to get a good back and swap it to your reproducer and see how much it really makes. My advice to you is to look for a complete reproducer which meets your criteria and either rebuild it or send it out for a rebuild.
Hope this helps.

Jim

[A Ford 1]

First I must thank both phonojim and edisone for there interest in my needs. The photos are very interesting in that from my grad school days I remember the Dr. Seigal's class Stress Waves in Continuous Media. Dr. Seigal, of The Naval Ordinance Laboratory, was known as the bigest gun in the east.
Looking at the photos and making a quick and not by any means complete evaluation it looks as if they were trying to minimize the distance between the diaphragm and the backing to cut down on cancellation of the high frequency waves bouncing back and forth as well as concentrating the high frequency waves from the diaphragm into the tone arm. I could be off in this quick look but it does perk my interest.
I have not yet disassembled my Orthophonic but looking in I see a bright metal three leg device that may be there to keep dumdums from probing the diaphragm and I hope it might indicate that this has a plug but since it all appears to be brass I have my reservations. Toward the end of the month a re-builder friend and I will disassemble the Othophonic and I will know for sure what I now have. I think I recall seeing the original bill for my Radiola-Borgia II being dated 1926 or 27 but it might have had modifications as the first owner Dr. Miller had also a Thermadin and an Ampico Grand piano.
Allen

[De Soto Frank]

How about a picture looking down the throat of your reproducer ?


If there is a round "blob" at the center of the three legs, it is probably a phase-plug. Phase plugs should be either black or dull-gray.

If the three legs just come together at a simple intersection, it's probably either the nickel-plated or die-cast guard to prevent mechanical injury to the diaphragm ( no intended acoustic benefit by design. )

[A Ford 1]

I thank every one for their help to date in this quest.
Allen