BLUE ARCTURUS

Although Brightson and others were making tubes with blue bulbs at least by 1925, Arcturus is the name that usually comes to mind when blue tubes are mentioned. This article will chronicle the early developments of Arcturus and present a listing of blue tubes made through mid 1933. Lists of blue Arcturus tubes can be found in various books and articles. Some of these lists contain types whose manufacture has not been verified by the author. These types will not appear in the main list but will be grouped together for reference.

The first mention of the Arcturus Company found was in September of 1927, with their initial ads running in October 1927. Their first series of tubes ran on 15 volts AC with carbon heaters.One heater lead was tied internally to the cathode. The result was an AC tube with a standard 4 pin base which could be used to "electify" battery receivers. There were 7 tubes in the 15 volt series with numbers running from AC22 to AC48. Arcturus did not use the "AC" prefix on the tube numbers in their ads, but the earliest production tubes were so marked on their bases. To avoid confusion with later types the AC prefix will be used here to describe the 15 volt types. The early ads made no mention of blue glass and indeed not all of the original 15 volt series had blue bulbs. The early production of the AC30 and AC40 (both power tubes) had clear tipped bulbs. Later versions had blue bulbs. The AC32 (hi-mu type) has been seen with an amber bulb, and other variations may exist. While this first series was not a huge commercial success, sales were sufficient to continue manufacturing into 1933 as evidenced by their inclusion in the Spring 1933 Federated Purchaser catalog.

The initial release of October 1927 consisted of the AC26 detector, the AC28 general purpose tube, and the AC30 power tube. Since the characteristics of the AC26 (Fig. 1) were very similar to the AC28, the AC26 saw little usage. By February of 1928 the AC32 high-mu tube (the first of its kind) had been added. June of 1928 is the first mention of the AC22 tetrode (Fig. 2) (also a first) , with the AC48 general purpose tube following in September. The AC40 (Fig. 3) is first advertised in December of 1928. An Arcturus data sheet in the authors collection lists all the 15 volt types and contains the following statement - "Arcturus manufactures a complete line of 15 volt A-C Tubes: Nos. 26, 28, 30, 32, 48, 40, 22 and 50." The last mentioned number 50 is of unknown design and no evidence of any actual production has been found to date.

In February of 1928 an article in Radio Engineering describes 15 volt tubes with side screw connections on the base for the heater. Arcturus sold harnesses to connect to these side screws to bring out to an AC supply. These harnesses were intended to simpify the conversion of battery receivers to AC. Types AC26, AC28, AC30 and AC32 were available with this construction. The AC28C is shown in Fig. 4. These types were described as the 26C, ect. in the article but the tube marking did not show the "C". However, some of the cartons for these tubes had a label on the bottom of the box which did include the C in the part number. The harness ready tubes were apparently not well received as the side screw equipped tubes are not often found.

The 15 volt tubes were intended for the electrification market, the converting of battery sets to AC filament operation. The large and messy storage battery normally used for the filament supply was eliminated, but B and C batteries were still needed. There was heavy competition in the AC conversion market, with companies like Kellog, Van Horne, Marathon, Sovereign and others all fighting for a slice of the business. The advent of all-electric AC sets from the major radio builders saw many battery sets junked rather than converted. Faced with a shrinking demand for their 15 volt tubes Arcturus soon moved into new areas. In September of 1928 they introduced their version of the '27 detector. First advertised as the 127AC, they were described as having a 7 second warm-up time. Despite the illustrations used in the ads, the early 127's had tips (Fig. 5). Additionally they were marked DETECTOR on the base. A tipped version marked 127A was also produced. No advertising for the 127A has been found, but a small article in the March 1929 issue of Radio Engineering states that the 127A was to replace the 127. The 127A had reduced interelectrode capacity and used the same heater assembly as the 127. All 127A's seen have tips, and are marked DETECTOR on the base. This number was only used for a while, as when production of the tipless tubes started the tubes were numbered 127. Before the conversion to ST (dome) bulbs ocurred in 1933/34 some 27's were made with the small S12 bulb rather than the normal S14 (Fig. 6).

In November of 1928 new AC tubes were announced. These were the 126H, 126, 071H, 071, and the 180. However, in some December ads the 071H was no longer listed. The 126H was a special heater version of the 126 and had the mid-point of the heater tied to the cathode. This arrangement allowed the commonly used hum balance pots across the filament leads to function normally. The internal construction of the 126H was quite different from the normal 126 (Fig. 7). A small internal capacitor was connected from grid to plate to provide the 126H with about the same grid-plate capacity as the standard tube. Since the '26 was mainly used in neutralized RF stages, similar capacitance was need to make the 126H a drop-in replacement. The 071H was a heater version of the 071 with the same mid-point heater connection. A sample in the authors collection drew a whopping 1.2 amps of heater current, but otherwise performed like a standard '71 (Fig. 8). Unlike the 126H, the heater was a single strand of uninsulated wire spaced relatively far from the cathode sleeve. This inefficent arrangement was probably the cause of high current required. Neither of these strange tubes sold well and were soon dropped from the line. The more standard 071 was also somewhat of an oddball in that it used a .5 amp oxide filament. The standard '71 used a thoriated .5 amp filament.

Starting in 1928 Arcturus made for Sonora a number of tubes which Sonora used in various combinations in some of their receivers. These included the RA-1 (Fig. 9), DE-1 (Fig. 10), RE-1, RE-2, SO-1 (Fig. 11) and SO-2. These were all equivalent to standard Arcturus types. The RA-1 and SO-1 were 15 volt types. These tubes are marked Sonora on the base but also carry the inscription "Made by the Arcturus Radio Company".

One of the early AC tetrodes on the market was introduced by Arcturus in April of 1929, first listed (and marked) as the 122 (Fig. 12). This tube was actually an early version of the UY224 and had a five pin UY base. Some confusion exists here for collectors as later Arcturus made another 122, this one the same as a standard UX222 with a 4 pin UX base (Fig. 13). Arcturus was not the only company to use the "22" designation on early 24's. Both CeCo and Everready Raytheon sold 24's marked AC22, while Sonatron and Sylvania used the number 222AC. The type number 122 was dropped in July of 1929 when Arcturus changed the designation to 124 in keeping with RCA.

During the late 20's and early 30's Arcturus expanded their tube line to include most of the standard types as made by RCA. Their battery line was limited to the 101A (Fig. 14), 012A, 122, 099UV (Fig. 15) and 099UX. The AC tubes used a quick heater construction and they stressed this feature in their ads, claiming a seven second warm-up time for AC tubes with indirect heaters. Other types available by January of 1930 included the 145, 150 (Fig. 16), 180 and 181.

By May of 1932 the PZH was added to the line. The original PZH was basically a 47 with an indirect heater, and was the first such tube on the market. After the introduction of the 2A5 by RCA, the PZH was redesigned to have similar characteristics. By early 1934 the PZH had been changed from a 6 pin to a 7 pin base, with the suppressor grid brought out to the added pin (Fig. 18). This was a strange move for Arcturus, for the PZH no longer crossed to the 2A5 and was not directly compatible with any other similar tube. The PZH is not common, and the few samples seen by the author were of the 7 pin variety.

Another new tube pioneered by Arcturus was the 551 (Fig. 19) variable mu tetrode, first sold in April of 1931. This was the first remote cutoff RF amplifier on the market and was of great value for use in Automatic Volume Control (AVC) applications. Conventional tubes were subject to considerable distortion and cross-talk when forced to deal with input signals of greatly varying levels. The 551 used with AVC reduced these effects to generally acceptable levels. Most samples of the 551 have the variable mu sign etched into the glass near the top of the tube. The 551 became an industry standard type and was interchangable with the 35/51 later sold by many companies.

By November of 1931 Arcturus was making the 2 volt battery tubes, types 130 through 133 (Fig. 20). Also available were the 6.3 volt types 136 through 138 (Fig. 21). These 6.3 volt types were first made by Arcturus and RCA for DC heater use only. They were redesigned for AC heaters and in February of 1932 Arcturus announced the types 136A, 137A, and 138A (Fig. 22). These new versions had a new M shaped non-inductive heaters intended for AC or DC use.

In June of 1932 types 46 (Fig. 23), 56, 57, 58, and 82 were announced. August of 1932 saw the addition of the 41, 42 (Fig. 24), and 44. The 41 is shown in one Arcturus brochure as the PA. No samples of a tube marked PA have been seen. By September the line included types 134, 55, 59, 83 (Fig. 25), 85, 89, and GA (Fig. 26). The GA was a 5 volt power pentode for DC use. Intended to replace the 71A in new designs, it had higher gain and greater output power capability. It did not catch on, and has no known usage in commercial receivers.

A major development occurred in July of 1932 when the Wunderlich special detector was announced. This tube had two co-planer grids which when properly driven caused the RF to cancel out leaving only the audio signal at the plate. The Wunderlich Type A had a 2.5 volt heater and was made in two different styles, a 5 pin with a top cap (Fig. 27) and a 6 pin without the cap (Fig. 28). The Type A Auto had a 6.3 volt heater and came only as a 6 pin (Fig. 29). The Type B had an extra element called the anode grid and could provide amplified AVC. The B had a 6 pin base with top cap and a 2.5 volt heater. The Type B Automotive was the same with a 6.3 volt heater. The B types are seldom seen and are not known to have been used in any receivers. The Wunderlich tubes had distinctive red bases, but employed a strangly lax marking code. Some were marked "Wunderlich" or "Wunderlich Automotive" but often they were not marked at all. An unmarked 6 pin tube could have either a 2.5 volt or 6.3 volt heater and careful testing would be needed to determine the rating.

In April of 1933 four more special tubes were announced, the AD, AE (Fig 30), AF (Fig. 31), and AG. The AD was a half-wave rectifier similar to the Type 1 but having a fuse in the plate lead. The types AF and AG were the same as the 82 and 83 but with protective fuses in the plate leads. In an Arcturus technical bulletin of May 1934 the AD and AE were no longer listed, and the AF and AG were shown only as reference designations to the 82 and 83.

The AE is somewhat of a puzzle. The AE characteristics and typical circuit are given in a Radio News article from April of 1933. This tube was a power tetrode, but with a plate of special design to minimize secondary emission and operated as a pentode. This is the classic description of a beam power tube and would have made the AE the first such tube on the market, three years ahead of the 6L6. The full potential of the beam power design was not fully exploited in the AE as it used a small ST-12 bulb and was only rated for 400 milliwatts output. The AE seems to have had no documented usage, and is not shown in any Arcturus or general tube listing the author has seen. There is then some question as to whether the AE was ever actually in production.

One other 1933 release of note was the 39/44. This tube replaced the earlier types 139A and 44, which had similar characteristics. The interesting feature of this tube is that some were made with blue bakelite bases, the only Arcturus tube known to use that construction.

The three digit number system was dropped before the use of blue glass stopped and almost all of the 100 series numbers can be found as two digit numbers. In some cases four different number variations were used. As an example the 137 became the 137A, was shortened to 37A and finally ended as the 37. Some later types can be found with clear bulbs but marked "Arcturus Blue" in blue paint. See Fig. 35 for a 37A built this way.

As mentioned at the beginning of the article, a number of blue Arcturus tubes have been seen in various lists that the author cannot verify as actually being in production. These types include the AC31, AC46, AC50, BA-1 (Sonora), and T1. This list is provided for reference, and inclusion on the list does not necessarily mean that any particular type listed was never made. Some tubes of low production are naturally very scarce, and some of these types may eventually be determined to have been in production.

The following is a listing of all Arcturus tubes known to have been initially made with blue bulbs. The cut-off date is mid 1933 at which time the word "Blue" was dropped from Arcturus ads. Since the use of blue glass was gradually phased out, later types like the 5Z3 are sometimes seen with blue bulbs but were not normally made this way. These later types are seldom seen and are highly desirable additions to the standard types.