revised 5/24/03

If RCA was the King Kong of early tube manufacturers then Conrad Schickerling must be considered as the King of Con. One of his early tube brochures carried the following statements concerning his "Z" rectifiers: "Nothing like it in the World - As mysterious and uncanny as radio itself". These captions would be a fair description of Schickerling's oddball tube designs, unique to be sure but lacking any technical merit.

Schickerling did almost no national advertising so the following description of his activities is mainly based on information from his tube brochures and articles/ads from sources like Radio Retailer and Jobber, Radio Engineering, Radio Dealer, and other relatively obscure sources. Information from these sources states that Schickerling started in the lamp business around 1898, but was forced out by GE at some later date. To hear Schickerling tell it, GE employed some underhanded means to put him out of business,[1] but no details are given and this may be just sour grapes on his part. These same sources give 1921 as the start date for his tube business, but no references can be found before 1923. The inception dates given for the various tubes are mostly best estimates based on fragmentary information as normal introductory advertising was not available. Due to the general scarcity of Schickerling tubes no claim is made that the types described in this article represent a complete list of his tubes.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

The first known Schickerling tubes were marketed by the T.V.T. Corporation of Newark, NJ. Although not specifically stated, the assumption is that TVT stood for Triangle Vacuum Tube. These tubes were composed of a number of small parallel triangular plates with a hole in the middle, through which the filament lead was placed. This weird design was clearly just a method to get around the DeForest triode patent. One of the first of these was the T.V.T. 11A, and had three triangles, two connected to the plate pin on the base, the other to the grid pin. This tube came in two forms, a pear shaped type (Fig. 1) and a tubular type (Fig. 2). This tube was listed as a dry cell type and rated for 2-3 volts on the filament. The filament current at 2.5 volts was .4 amps. The other known triangle tube was the T.V.T. 200, and was essentially the same except five triangles were used, three plate and two grid. A pear shaped sample is shown in Fig. 3. The paper label is missing from this sample. This tube also came in a tubular bulb version as shown in Fig. 4. The T.V.T. 200 was a storage battery tube with a 4-5 volt filament rating.

An examination of the structure shown in Fig. 3 leads to an obvious conclusion. The arrangements of the elements would allow for little control of the plate current by the grid voltage impressed on the triangle elements. The measured plate current of a TVT 11A with zero bias and 45 volts on the plate was 5 Ma. The author and others[2] have tested "functional" samples of both the TVT 11A and the TVT 200 and were only able to measure Gm's in the range of 30 to 50. In receiver tests these tubes showed almost no function at all.

s 8pin
Fig. 5

s 8pinb
Fig. 6

Another early triangle plate tube is shown in Fig. 5. This tube was advertised in 1923 and is shown in one Schickerling brochure, but no specific designation was given. The description of "New Radio Dry Cell Tube" was used in the 1923 ad, and a price of $6.00 shown. The internal structure was similar to the TVT 200 except for the filament. Although not really visible in the photo, the filament was a V type with a connection at the mid-point. The base of this tube is shown in Fig. 6. All five triange elements had leads brought out, plus two for the filament and one for the mid point. This made a total of eight connections and thus the strange base. It might be assumed that Schickerling offered a matching socket for this tube, but no info is available. This might have been the first of the triange plate tubes. The market for a tube with this highly unconventional base would have been very small, and a quick redesign to the TVT 200 style would seem a logical next step. The illustration in the brochure is even more bizarre than the tube. The illustration shows the eight pins all in line rather than the actual circular pattern used. It also shows two of the pins as being threaded! It's hard to imagine a more user-unfrendly arrangement.

Schickerling managed to sell some of these strange tubes, but based on the number of surviving samples not many. To the unsophisticated buyer of 1923 you could expect to sell some quantity of almost anything that was new and different, but word spread quickly about bad products. Since for all practical purposes these tubes didn't work, he needed something new to sell with real function. His solution was to use a more convention structure but surround it with a "stabilizing element" of somewhat triangular shape to maintain the TVT tie-in. This new element was generally tied to the filament and was claimed to shield the tube from static and all other forms of noise or interference. He continued to call his tubes "triangle plate radio tubes"[3] and now added the description of "four element tubes". This new element was totally bogus, as it had neither the proper shape nor size to have any significant shielding effect. Even a fully shielded tube would have no effect on static or other signal related noises. Schickerling was apparently unconcerned about anybody copying his useless gimmick, as he didn't bother to apply for a patent on the stabilizing element until February of 1925. The patent (1,687,897) was granted in October of 1928.

Fig. 5

Fig. 6

Fig. 7

Fig. 8

In 1923 the first of these new tubes was released, the S100. This tube was a 5V detector and has been seen with both a tubular style (Fig. 5) and standard style bulb (Fig. 6). The stabilizing element fanned out to three sections at the top of the tube. The S100 seems to be the only tube that used this three-section stabilizer. From what can be found in his brochures, it appears that the S100 was not made past 1924, being replaced by other types. From 1923 through early 1924 seven new types were released, starting with the S200.[4] This tube was a 5V gas detector and is shown in Fig. 7. This tube was claimed to be very sensitive and required careful adjustment of operating voltages. The S300 was a detector/amplifier and had a 1.5V .25A filament (Fig. 8). It was claimed to be a WD-12 replacement, and had the same general operating voltages specified. The S400 was a 3V, .1A detector/amplifier, and could be used in '99 type applications, but required a socket adapter for this purpose. This tube has been seen with both a brass UV base (Fig. 9) and a nickel Shaw base (Fig. 10).

Fig. 9

Fig. 10

Fig. 11

During 1923 the company name was changed to the "Schickerling Products Manufacturing Co.".[5] Somewhat later there was a corresponding change in the company logo, see Fig. 11. The left-hand image is the earlier logo used with the T.V.T. Corporation. The right-hand logo is almost the same but has the Conrad Schickerling name added across the middle. Tubes marked with the left-hand logo would represent earlier production than the others. A number of the early S series tubes can be seen with either type of marking.

Fig. 12

Fig. 13

Fig. 14

Fig. 15

Another tube of this period was the S500. This tube was primarily used as an amplifier although listed as a detector/amplifier. This tube has been seen in a variety of bulb and base styles as shown in Figs. 12, 13, and 14. The spherical versions are the earliest, while the standard bulb sample is of later production. An internal view of this tube is shown in Fig. 15. Note that the stabilizer has been changed to a two-section type. Also worthy of note is the fact that the stabilizer is tied to the plate rather than the filament. Even Schickerling would have a hard time explaining how such an arrangement could provide any measure of shielding. These tubes were initially listed as having a max plate voltage of 90, but later data shows the figure as 120 volts.

Examination of a number of these early tubes shows that many of the bases came from other manufacturers. The Shaw brass bases are commonly old Moorhead/Marconi/DeForest bases with most of the original markings ground off, but often have enough old marking left to be identified. The nickel Shaw bases are of the type used for the early DeForest DV-6 tubes. The bases carry only the marking "PAT APL'D FOR" and no attempt was made to remove this marking. It appears that Schickerling purchased surplus bases to reduce his manufacturing costs. This practice explains the multiple variations that can be found in the early types. There are likely other base/bulb combinations used by Schickerling that are not pictured in this article.

Fig. 16

Fig. 17

The S600 was a dry cell tube with a UV199 type base (Fig. 16) and intended for the same type of applications. This tube was later superceded by the S8100. Next in the series was the S700, a power tube. This tube has been seen only with a large spherical bulb (Fig. 17) and would handle 150 volts on the plate. Intended as an output tube to drive a speaker, no output power rating has been found to date. The S800 was an RF amplifier with a standard 5 volt, amp filament rating. No picture was available for this tube, so the exact form is not known.

Fig. 18

Fig. 19

Fig. 20

Fig. 21

An additional six types came on the market between early 1924 and early 1925.[6] The first of these was the S900 (Fig. 18). No data has been found for this type, but the base marking says that it was a 5V, .1A amplifier for use at 45-90 volts on the plate. Apparently the number S1000 was skipped, as no mention has been found of that type. The S1100 was an RF amplifier with a 5V, .1A filament rating. This tube had a standard bulb (Fig. 19) and does not appear in any brochures seen so far. The S1600 was a detector/amplifier with the unusual filament rating of 5V, .16A. The bulb was a large tubular type (Fig. 20) and the plate assembly was a horizontally mounted flat type, typical of many Schickerling tubes (Fig. 21).

Fig. 22

Fig. 23

The next number in the series was the S2000. This was a detector/amplifier with a 5V, .1A filament. No picture is available so its form is unknown. The S2500 was described as an oscillator-amplifier and is shown in Fig. 22. The S2500 had a 5V, .25A filament and a max plate voltage of 120. The S4000 (Fig. 23) was Schickerling's equivalent to the '01A and the most often seen of his tubes. This was a standard 5V, .25A filament tube and was probably sold in much higher quantities than any of his other tubes.

By early 1925 the company name had changed again,[7] this time to the "Schickerling Products Corporation". Distribution of Schickerling tubes seems to have ranged from direct sales at the factory and mail order[8] to distribution through large chains like the United Cigar Stores, which had about 1500 outlets.[9] Sales appear to have been mainly on the East Coast, and his corporate Sales Offices were located in New York City and Philadelphia. Promoting his useless "four-element" construction, he kept his prices higher than other independent tube manufacturers. His S4000 retailed at $2.50 in late 1925, the same price as the equivalent '01A from RCA.

Fig. 24

Fig. 25

Several new types appeared in 1925. The S8100 (Fig. 24) had a UV199 style base and was described as a direct replacement. The rated filament current was slightly higher at .08 amps. The introduction of the S8100 was accompanied by special hoopla on the part of Schickerling because it was his first (and also apparently his last) use of "radium glass". He claimed that radium glass was his invention, and that it had a distinctive green color. He fails to mention, however, exactly how radium glass improves his tube. A statement on this subject from one of his brochures[10] is worth reprinting. "This glass of greenish iridescent color gives through its radium activity a most remarkable result in radio tube construction." Well, did it glow in the dark? Did it make your fingers tingle? Clearly he has nothing meaningful to attribute to the use of radium glass. Later brochures did not mention this feature in conjunction with the S8100, and "radium glass" was not heard of again. The S8100 was also made in a bakelite base version (Fig. 25) and is the only "S" series tube known to be made in bakelite.

Fig. 26

Another 1925 offering was the Z50 half wave rectifier (Fig. 26). This tube was a neon gas rectifier rated for 50 Ma output. This tube was priced at $5.00.[11] An early form of this tube is described in an article in Radio News for September of 1925. Apparently this early form was more robust as much higher output currents are discussed. The article mentions that an essentially identical tube had been in production for several years by the German firm Hydra-Werke of Berlin. Despite this fact Schickerling advertising would imply that the "Z" tube was an invention of his own.

1926 saw the introduction of the SX series tubes. These were bakelite based UX types in keeping with the rest of the tube industry. These tubes normally had paper serial number labels on the bulb with a matching serial number on the carton. His numbering system becomes confusing at this point for the collector because of the infusion of conventional construction tubes at the same time. While all of the S series tubes were of the four-element type, only some of the SX tubes had that feature. To add to the confusion, some of the SX series tubes were the same as their S series counterparts, the only difference being the base. Others, however, were quite different from the S series tube of the same number. To help sort out this mess, the following paragraphs will only deal with the known SX tubes of the four-element type, while tubes of conventional construction will be discussed later.

Fig. 27

Fig. 28

The SX100A was an alkali vapor detector, similar to the UX200A. Note in Fig. 27 that the stabilizing element had been reduced to a rather small stamped out piece of metal. Since this piece did nothing, it made sense to make it as small and cheap as possible. Ever the huckster, Schickerling brochures[12] of the period continued to claim that because of this feature, "Absolute noiseless reception is assured".

The SX112 and SX171 are shown in Fig. 28. (The same cut was used for both tubes in the brochure.) These power tubes were equivalent to their RCA counterparts. The SX200 detector was listed as a replacement for 200 type tubes, but employed a 5V, .25A filament. The SX210 was like the UX210. The same illustration shown in Fig. 28 was used for the SX200 and the SX210. For the SX210 this cut is almost certainly incorrect. It came from the same brochure[13] that listed the 112 and the 171 and appears to be the same cut used for these lower power tubes. This same brochure also shows identical pictures for the Z50 and Z80, which are known to be quite different.

Fig. 29

Fig. 30

The SX500 was something new; a tube described as a "Certified Characteristic Radio Frequency Tube". A sales brochure shows this tube as having a special paper label with measured readings of Gm, u, and Rp indicated. The brochure also shows this tube as having a brass UV base; an obvious error as the SX designated UX based tubes. On the sample in Fig. 29 the base itself is marked "Certified" and the label is not present. The SX700 was a power tube essentially the same as the S700 in electrical specs, and used the same large spherical bulb (Fig. 30). This tube was also recommended for use as an oscillator.

Fig. 31

Fig. 32

Fig. 33

The SX1200 was a small output tube listed as a UX120 replacement (Fig. 31). At this point in time a larger percentage of Schickerling's special tubes were being designed to cross directly to standard RCA product. The SX4000 (Fig. 32) was equivalent to the UX201A and is the most often seen of the SX series tubes. The SX8100 was the same as the S8100 except it had a UX base (Fig. 33). This tube was described as a replacement for the UX199 and had similar specs.

Fig. 34

Fig. 35

Fig. 36

Fig. 37

A new series of tubes appeared in 1926, described as the "Precision Type".[14] These tubes incorporated lava insulators at each end of the plate, which served to anchor the grid and filament leads. Schickerling claimed that this arrangement made the tubes totally non-microphonic.[15] The other construction details were the same as his other tubes. The P.S. 10 (Fig. 34) was an amplifier rated for 45 to 120 volts on the plate. The P.S. 12 (Fig. 35) was for use as a detector at 16 to 45 volts. Last in the series was the P.S. 15 (Fig. 36) a power tube that strongly resembles the SX700.

Also appearing about this same time was the High-Mu 20 (Fig. 37), a tube apparently similar to the Daven MU-20 and intended for use only in resistance coupled amplifiers. The illustration shows a brass UV based tube, but most likely this tube was actually in a bakelite UX base.

A February, 1926 article in Radio Retailer and Jobber provides some interesting information about Schickerling's position regarding tube patents held by RCA. He had made earlier the ridiculous assertion that because of the presence of the stabilizing element his tubes had not infringed the DeForest patent.[16] However, since the DeForest patent had expired in early 1925 this was a moot point. He was concerned about other patents however, and stated that his tubes contained no tungsten so were not subject to suit on that issue, using instead a special composition filament of unspecified material. He also pointed out that his tubes were not of the tipless variety and so not liable on that point. Indeed Schickerling ads as late as 1929 show tipped tubes. However, tubes he started making in 1926-1927 of standard design did not employ tips. A typical example of a standard tube is shown in Fig. 38. This is an SX200A and is just a regular 200A detector, no different from those made by many other manufacturers.

Fig. 38

Fig. 39

The only unique tube from Schickerling in 1927 was the Z80 full wave rectifier. Rated at 80 Ma output, this was really a thinly disguised version of the Raytheon BH. The main difference was in the strange looking anode assembly (Fig. 39). Never relenting on the hype, he described this tube as a four-element type.[17] Apparently the small horizontal disk just above the anode was the fourth element, but it's unclear what possible function he could have claimed for this disk in a rectifier. He dubbed this tube as part of a new "Corona" series, but no other Corona tubes have been seen.

From 1927 onwards his new products were mainly generic types built in the normal fashion, but he continued to sell a number of his four-element types. He was apparently moderately successful as by 1927 he was sponsoring a radio show featuring a musical group called the Schickerling Crystal Gazers. Four stations on the East Coast initially covered this broadcast.[18] In late 1928 Schickerling was forced into receivership by manipulations of RCA regarding Schickerling dealers. Several were threatened with being cut-off from new RCA receivers if they did not equip these receivers with RCA tubes rather than Schickerling tubes.[19] This action was the result of RCA's use of the infamous "Tube Clause No. 9". He rebounded quickly and by October of 1928 had established the new company of "Conrad Schickerling, Inc." at his old location.[20]

Fig. 40

The last four-element tube known to be introduced by Schickerling was the SX371B of early 1929 (Fig. 40). It's not clear if this tube was tipped, as ads show it both ways. The SX371B was claimed to have a 50% longer filament[21] giving extended life. In March of 1929 the company was once again reorganized,[22] this time as the "Schickerling Radio Tube Corporation". At this time it was stated that twenty-one different kinds of tubes were in production.

Schickerling remained in business into the thirties, but was gone by the forties. The combination of strange designs and scarcity has made his early tubes into highly collectable items today. He was a consummate con man, for he managed to stay in the tube business for ten years plus on the basis of claims made without a shred of truth. He claimed to have over ninety patents related to tube manufacturing, but a search of patent records shows only a few. He even went so far as to state that his worthless stabilizing element put his tubes in the category of shield grid tubes (tetrodes), with his being earlier.[23] Apparently with the right pitch you can sell almost anything.

The author is indebted to many people who supplied copies of scarce Schickerling brochures and other materials; in particular Alan Douglas, Lud Sibley, Joe Knight, Tim Tromp, Larry Daniel, and others whose contributions helped make this article possible.

The table below is a summary of available information for known early Schickerling tubes. Tubes of convention construction that he started making around 1926 are not listed.

8 pin tvt DET T S/BR 4-6V NA
TVT11A DET P, T S/BR 2-3V/.4A 16 - 45V NA
TVT200 DET P, T S/BR 4-5V 16 - 45V NA
S100 DET P, M UV/BR 5V/.1A 16 - 45V NA
S200 GAS DET P, T UV/BR 5V/.25A 16 - 45V NA
S300 DET/AMP T UV/BR 1.5V/.25A 22 - 45V 45 - 90V
S400 DET/AMP P, T, S UV/BR, S/N 3V/.1A 22 - 45V 45 - 90V
S500 DET/AMP P, S UV/BR, S/N 5V/.25A 22 - 45V 45 - 90V
S600 DET/AMP T UV99/BR 3-4V/.08A 22 - 45V 90V
S700 POWER S UV/BR 5V/.25A NA 90 - 120V
S800 RF AMP --- --- 5V/.25A --- ---
S900 AMP P UV/BR 5V/.1A NA 45 - 90V
S1100 RF AMP P UV/BR 5V/.1A NA 90 - 120V
S1600 DET/AMP M UV/BR 5V/.16A 22 - 45V 45 - 90V
S2000 DET/AMP --- UV/BR 5V/.1A --- ---
S2500 DET/AMP M UV/BR 5V/.25A NA 20 - 120V
S4000 DET/AMP P UV/BR 5V/.25A 22 - 45V 45 - 120V
S8100 T UV99/BR,BAK 3-4V/.08A 22 - 45V 45 - 90V
SX100A ALK DET P UX 5V/.25A 16 - 45V NA
SX112 POWER P UX 5V/.50A NA 90 - 135V
SX171 POWER P UX 5V/.50A NA 90 - 135V
SX200 GAS DET P UX 5V/.25A 16 - 45V NA
SX210 POWER P UX 7.5V/1.25A NA 250-350V
SX371B POWER P UX 5V/.25A NA 90 - 135V
SX500 RF AMP P UX 5V/.25A 22 - 45V 90 - 135V
SX700 POWER S UX 5V/.25A NA 90 - 160V
SX1200 POWER T UX99 3-4V/.12A NA 90 - 135V
SX4000 DET/AMP P UX 5V/.25A 22 - 45V 40 - 120V
SX8100 DET/AMP T UX 3-4V/.1A 22 - 45V 45 - 90V
P.S. 10 AMP M UX 5V/.25A NA 45 - 120V
P.S. 12 DET M UX 5V/.25A 16 - 45V NA
P.S. 15 POWER S UX 5V/.25A NA 90 - 160V
HIGH-MU 20 AMP P UX 5V/.25A NA 90 - 200V
Z-80 RECT P UX NA NA 80 Ma



[1] "Conrad Schickerling - A Brief Biography", Radio Retailer and Jobber, Feb, 1926, p. 48

[2] Alan Douglas, "The Schickerling Tube", Old Timers Bulletin, June, 1986, pp. 20, 21

[3] Schickerling tube brochure, ca 1923

[4] Schickerling tube brochure, ca 1924

[5] Schickerling tube brochure, ca 1923

[6] Schickerling tube brochure, Feb, 1925

[7] Schickerling tube brochure, Feb, 1925

[8] Ludwell Sibley, "More on Schickerling", Tube Collector, Feb. 1999, pp. 11-13

[9] "The Programme To Make Schickerling Tubes Lead The Procession As Pre-Eminent Audions", Radio Retailer and Jobber, Jan, 1926, p. 43

[10] Schickerling tube brochure, Aug. 1925

[11] "The Radio Dealer Catalog of New Apparatus", The Radio Dealer, Aug. 1925, p. 121

[12] Schickerling tube brochure, 1926

[13] Schickerling tube brochure, 1927

[14] Schickerling tube brochure, 1926

[15] "A Non-Microphonic Vacuum Tube", Radio News, Jan. 1926, pp. 985, 1073

[16] "Schickerling Denies Suit", Radio Retailer and Jobber, Dec. 1925, p.46

[17] "Schickerling Shows All-Wave Filamentless Rectifier", Radio Retailer and Jobber, Jan. 1927, p. 51

[18] "Schickerling Shows All-Wave Filamentless Rectifier", Radio Retailer and Jobber, Jan. 1927, p. 51

[19] "RCA And Its Circuit Licensees To Be Sued For $8,000,000 Damages", Radio Retailer and Jobber, Nov. 1928, pp. 1, 6, 32

[20] "RCA And Its Circuit Licensees To Be Sued For $8,000,000 Damages", Radio Retailer and Jobber, Nov. 1928, pp. 1, 6, 32

[21] "Schickerling Creates Furore With New SX-371B Tube", Radio Retailer and Jobber, Feb. 1929, p. 28

[22] "More Schickerling Details", Radio Retailer and Jobber, Apr. 1929, p. 46

[23] Schickerling lamp brochure