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Mershon, Ralph D.; New York City

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Name: Mershon, Ralph D.; New York City    (USA)  
Abbreviation: mershon
Products: Model types

The full name is Ralph Davenport Mershon. He was a power engineer. He was born July 14, 1868 at Prospect Place on Hamline Hill in Zanesville, Ohio and died February 14, 1952 at 2000 Tiger Trail Avenue, Cocoanut Grove, Florida. His parents names: Ralph Smith Mershon & Mary E. Jones Mershon.

Text from Wikipedia, October 24, 2010:
"Retired US Navy engineer Ralph D. Mershon is credited with developing the first commercially available "radio" electrolytic capacitor that was used in any quantity (although other researchers produced broadly similar devices). The "Mershon Condenser" as it was known (condenser was the earlier term for capacitor) was constructed like a conventional paper capacitor, with two long strips of aluminum foil interwound with strips of insulating paper, but with the paper saturated with electrolyte solution instead of wax. Rather than trying to hermetically seal the devices, Mershon's solution was to simply fit the capacitor into an oversize aluminum or copper can, half-filled with extra electrolyte. These units are referred to as "wet electrolytics," and those with liquid still inside are prized by vintage radio collectors.

"Mershons" were an immediate success and the name "Mershon Condenser" was, for a short time, synonymous with quality radio receivers in the late 1920s. However, due to a number of manufacturing difficulties, their service life turned out to be quite short and Mershon's company went bankrupt in the early 1930s."

We believe that Mershon was never in the Navy, but was a Lt. Colonel in the Army during WW1, detailed to the Naval Consulting. and we have been informed that his original interest in electrolytic capacitors was to improve the operation of high-voltage AC motors, and his experimental work was on AC capacitors (there being no market for DC capacitors at first). Between 1911 and 1942 he obtained 55 patents on electrolytic capacitors, and most of his income was from royalties.
Upon his death in 1952 the bulk of his estate, $7 million, went to Ohio State University. He never married; his three brothers had died in infancy and his sister survived him by a year.
Board. In "The Crosley Broadcaster* Vol. VIII (No. 3), February 1, 1929 features the Merhon Condenser in a full paged add: "Made exclusively by the AMRAD Corporation, Medford Hillside, Mass. The topic is "self-healing in case of puncture".

Here some of the text by Leland Roy about Ralph Davenport Mershon, written for OSU, Ohio State University:

"R.D. Mershon began his engineering career at the age of 17 as a member of an engineering corps engaged in railway location and construction. In 1886, after graduation from the Zanesville High School, he entered Ohio State University. During his last year at the University he was a Student Assistant in Physics and Electrical Engineering, and for one year after his graduation was Assistant Instructor of Electrical Engineering. He received his M. E. in E. E. in 1890 and the following year became associated with the Westinghouse Electric and Manufacturing Company, in whose employ he remained until 1900.

The transformers for which the Westinghouse Company received an award at the World's Columbian Exposition at Chicago in 1893 were of his design. From 1893 until 1895 he had charge of work being done by the Westinghouse Company in connection with the extension of the transmission plant of the Telluride Power Transmission Company of Telluride, Colorado. This was a single phase, alternating-current transmission, employing single-phase, synchronous motors.
The following year at Telluride he carried on investigatoins of phenomena which occur between conductors at high voltages for the Westinghouse and Telluride Companies. This investigation was made on a transmission line about two and a half miles long, and was the first investigation in which quantitative measurements of the ionization and other atmospheric losses occurring between conductors at high voltages were obtained. Original methods of investigation were devised by Mr.
Mershon for this work, and special apparatus was designed and built by him, by means of which quantitative measurements were made up to 72,000 volts.

Among his more important inventions being manufactured under his patents are:
The Six-Phase Rotary Converter, for converting alternating current to direct current; the Compound Rotary Converter, using an artificial reactance in series with the alternating current side of the rotary converter; a system of Lightning Protection for electric apparatus, especially applicable to high voltage circuits; a System of Protection against the Possibility of Fire in case of installations of oil insulated transformers; a Compensating Voltmeter enabling the indication at any point of a transmission system of the voltage at any other point, without the use of pressure wires.

Among his more important technical papers are:
"The Output of Polyphase Generators and Rotary Transformers," which contained the first published analysis of the effect upon the output of closed coil windings, when the number of phases is varied. "Drop in Alternating Current Lines," treating of the calculation of drop and giving a table and chart by means of which such calculations can be quickly and accurately made.
"The Maximum Distance to Which Power Can be Economically Transmitted."
"High Voltage Measurement at Niagara," which gives the result of some three years of investigation of the ionization and other atmospheric losses occurring between line conductors at high voltages. This was a continuation of the work previously done by Mr. Mershon at Telluride.

He was awarded the John Scott Medal for a Volt Meter Compensator by the city of Philadelphia, and received the Lamme Medal in June, 1932. This medal is awarded annually to an alumnus of the College of Engineering at Ohio State who is outstanding in his field. He maintains his own laboratory in New York City, where he is constantly working on improvements of existing inventions and on new inventions."

This article was written in 1934. No word about the Mershon condenser ...

But there is an US patent number 1728691 with the title "Electrolytic rectifier" with publication date 09/17/1929, filed Oct. 21, 1919. There is no word about radio. He states the problems of the known electrolytic rectifiers, consisting of aluminium electrodes and electrolyte like sodium phosphate and that they suffer by wasting away the film coating. The chief object of the patent is that filming electrodes will be automatically rewnewed as they waste away. He also filed a patent "Electrolytic condenser" (besides many others) which was pubilshed November 29, 1932 as number 1889416 and filed November 9, 1929 in New York. It is about interleaved electrodes to overcome some problems. The application for radios was not named. There is a match of 50 patents in his name, most of them about electrolytic devices. Alan Douglas wrote us: "Ralph Davenport Mershon was a power engineer. I believe, from memory, that he developed an electrolytic device for surge protection on power lines, and that his patents also happened to cover electrolytic capacitors. Amrad was the first to make such devices, but it took quite a while to turn them into reliable components for radio use. Crosley eventually (1931 or so) sold off the Mershon operation to Magnavox in Fort Wayne, Indiana."


Further details for this manufacturer by the members (rmfiorg):

Amrad made the first Mershon electrolytic condensers for radios. Picture from "The Crosley Broadcaster", Vol. VIII, No. 3., February 1, 1929, page 11 was sent by a guest.tbn_mershon_condenser_1.jpg

Forum contributions about this manufacturer/brand
Mershon, Ralph D.; New York City
Threads: 1 | Posts: 13
Hits: 1578     Replies: 12
Kolster 'B' Socket Power Unit HELP
Mark Skala

Recently I purchased an old Kolster "B" Socket Power Unit with the hopes it would work and fit in with my old battery radios. It does not work. The large condenser is blown. I cannot locate a schematic but do have the following information from the condenser:

Mershon Electric Condenser
Cap Total=30 Per Anode=10

Patents range from 1911 - 1927

There are three (3) taps on the top. It is about 6 inches high and 3 inch diameter.

My question is: what is a recommended replacement? How big (this one is rather large)? Where is the ground if the taps on the top are all positive? Can I simply use modern electrolytics?

Any assistance would be helpful.

Thank you,



Alan Scott Douglas † 16.11.15

It is a 3-section electrolytic capacitor; the copper can is negative for all 3 sections.  It was liquid-filled. Ordinary "dry" electrolytics will work fine as replacements, but you should probably monitor the voltage with no load to be sure it doesn't exceed 450V.

Mark Skala

Mr Douglas,

Thank you for your information. I did find where the negative lead is attached to the base of the can. Although modern dry electrolytics would work fine, if a wet cap were available would it be better?

As far as the values, I'm not sure if they are in Farads or microfarads. What would be used for a device of this type?




Alan Scott Douglas † 16.11.15

10 microFarads is right.

"Wet" electrolytics  were the first ones developed; later (and now) the liquid electrolyte is contained in an absorbent layer between the anode and cathode foils.


Wet electrolytics have certain advantages but are physically so large and prone to leakage that they haven't been made since the 1930s.

Mark Skala

Mr Douglas,

Thank you for the valuable information!

I believe they also used a bleeder cap with these? (there is a small one by the transformer) Guess that won't be needed any longer?




Alan Scott Douglas † 16.11.15

"Bleeder" is normally applied to resistors.


If there's another capacitor it could be a bypass for one of the lower-voltage outputs, or it could be a power-line bypass to reduce noise.  It would be a paper capacitor, and is almost certain to be leaky.  A B+ bypass would be 1 or 2 µF, and a line bypass would be 0.1µF or less.


Incidentally, I am unable to find a Kolster schematic that uses a Mershon capacitor.  Is this a power pack for a particular radio, and is it identified in any way?

Mark Skala

Mr. Douglas,

This is a power supply for old farm radios. It provides 4 voltages. The taps are labeled for B-, 22, 67, 90 and 135. No other information other than:

Kolster "B" Socket Power Unit

60 cycles 115 Volts 25 Watts
Manufactured Under Patent No. 1,455,141 - May 13, 1923
Other Patents Pending
Serial No __________
Manufactured By Federal Telegraph Co
Brandes Products Corp for
Federal - Brandis Inc
Newark New Jersey

Hope this helps,


Alan Scott Douglas † 16.11.15

The name "Federal-Brandes" dates it before April 1928, and the use of the Mershon capacitor dates it after 1927.  


There should be a tapped bleeder resistor to supply those voltages, and I would expect each tap to have a bypass capacitor.  Some B-eliminators used series resistors, so the voltage would only be accurate when a load is being drawn.  

Mark Skala

Mr Douglas,

I did see a large resistor. I will look at it more in depth this week and get back with you. Thanks much for your help!

Kind Regards,


Mark Skala

Mr. Douglas,

I tore it apart this evening, installed three new 10mfd/450vdc caps. There is still a smaller .67mfd cap rivited to a non-conductive base. Unfortunately my meter cannot test these caps so I do not know how stable it is. It is encased in a rectangle metal can about 2"x 9/16"x 1 1/4" in size.

The terminals are all part of a large resistor with multiple taps. I measured to ground and had the following results:

TAP 22 VDC = 55-56 Mohms
Tap 67 VDC = 97-117 Mohms
Tap 90 VDC = OFF Scale
Tap 135 VDC = OFF Scale

When powered on voltages are as follows:

22 VDC = 24VDC
67 VDC = 100+ VDC
90 VDC = 314 VDC
135 VDC = 314 VDC

There seems to be a problem with the resistor. I'm not sure I can calculate what the resistor values should be without knowing the proper output voltage of the transformer?

Thanks for your help,







Alan Scott Douglas † 16.11.15

The resistors should be in the thousands of ohms.  There are schematics of competitive brands of eliminators in the Rider manuals.  I doubt if there was ever a Kolster schematic published.  I have a Kolster service manual from this period and it's not there.

All the paper capacitors will be leaky by now; it's very rare to find one that is still good.

I would recommend asking on the Forum at, which is geared more to back-and-forth discussions of troubleshooting procedures.  You may also find someone there who owns one.

Georg Richter


please allow me some remarks:

Discussions about a certain model should not start from the manufacturer, but from the model page.

If the model is missing in the databse the model has to be suggested  to the RMorg model database, using "Create a new model" on the "home" page.

If the model is accepted it is fine and helpful to upload pictures. If you are not firm how to proceed please read the FAQ section for details. Later this thread can me moved to the model, to free the manufacturer site from discussions without details about the company.

Please don't leave this thread without updating informations from anywhere and about further progress of troubleshooting.

Thanks and Best Regards,


Mark Skala

I have submitted a new model for consideration as suggested. Thanks!

Mershon, Ralph D.; New York City
End of forum contributions about this manufacturer/brand