In the field of electronics , the EF50 is an early all-glass wideband remote cutoff pentode designed in 1938 by Philips . It was a landmark in the development of vacuum tube technology, departing from construction techniques that were largely unchanged from light bulb designs. Initially used in television receivers, it quickly gained a vital role in British radar , and great efforts were made to secure a continuing supply of the device as Holland fell in World War II .
106-493: The EF50 tube is a 9-pin Loctal -socket device with short internal wires to nine short chromium-iron pins. The short wiring was key to making it suitable for Very High Frequency (VHF) use. Early vacuum tubes were built using light bulb techniques, which had been highly automated by the 1920s. In a standard light bulb of the era, the tungsten filament was supported on two metal rods, which were fastened together by inserting them into
212-568: A spigot ) in the center. Octal sockets were designed to accept octal tubes, the rib in the keyed post fitting an indexing slot in the socket so the tube could only be inserted in one orientation. When used on metal tubes, pin 1 was always reserved for a connection to the metal shell, which was usually grounded for shielding purposes. This reservation prevented tubes such as the 6SL7/6SN7 dual triodes from being issued with metal envelopes, as such valves need three connections (cathode, grid, anode) for each triode (making six total) plus two connections for
318-458: A 36-degree angle between the nine pins of 1.016 mm thickness, in an arc of diameter 11.89 mm. European tubes of this type have numbers 80-89, 180-189, 280-289, 800-899, 8000-8999. The Duodecar B12C base (IEC 67-I-17a) has 12 pins in a 19.1 mm diameter circle and dates from 1961. It was also called the Compactron T-9 construction/E12-70 base It is generally similar in form to
424-425: A Noval socket, but larger. In the center is a clearance hole for a tube evacuation pip, which is typically on the bottom of a Compactron tube. (It should not be confused with the similar-sounding but differently sized Duodecal B12A base.) The Rimlock (B8A) base is an eight-pin design with a pin circle diameter close to Noval, and uses a nub on the side of the envelope to engage with a guide and retaining spring in
530-499: A cap, this also allowed the plate to run at higher voltages (over 26,000 volts in the case of rectifiers for color television, such as the 3A3, as well as high-voltage regulator tubes.) A few unusual tubes had caps for both grid and plate; the caps were symmetrically placed, with divergent axes. The earliest tubes, like the Deforest Spherical Audion from c. 1911 , used the typical light bulb Edison socket for
636-538: A charitable trust was created; representatives of the purchasing local authorities became the trustees with the duty to keep both building and park "available for the free use and recreation of the public forever". In 1921 a plaque was erected at the entrance of the south terrace in honour of Burt. The Palace passed into the hands of the Greater London Council in 1967, with the proviso that it should be used entirely for charitable purposes, and their trusteeship
742-409: A concert hall, art galleries, a museum, lecture hall, library, banqueting room and large theatre. The stage of the theatre incorporated machinery which enabled special effects for the pantomimes and melodramas then popular – artists could disappear, reappear and be propelled into the air. The theatre was also used for political meetings. An open-air swimming pool was constructed at the base of the hill in
848-460: A couple of hundred. It was intended that the theatre would reopen, but much costly restoration would be required first. It will never again reach a seating capacity of 3,000 (not least because one balcony was removed in the early part of the 20th century as a fire precaution, when films started to be shown there). A major season of the theatre company Complicité was planned for 2005 but the project, which would have included some repair and access work,
954-432: A cylindrical metal electrostatic shield that surrounded the tube, fitted with a spring to hold the tube in place if the equipment was subject to vibration. Sometimes the shield was also fitted with thermal contacts to transfer heat from the glass envelope to the shield and act as a heat sink , which was considered to improve tube life in higher power applications. Electrolytic effects from the differing metal alloys used for
1060-469: A fire started under the organ and quickly spread. It destroyed half the building. Again the outer walls survived and the eastern parts, including the theatre and the BBC Television studios and aerial mast, were saved. Parts of the famous organ were destroyed, though it had been dismantled for repairs so some parts (including nearly all the pipework) were away from the building in store. Some of the damage to
1166-401: A glass tube and then heating the glass and squeezing it flat with the rods inside. The resulting support was known as the "glass pinch". The pinch was then inserted into a larger glass envelope, the bulb itself, welded, and then fit with a metal cap for the electrical connections. For vacuum tube use, little was changed, with the various internal components supported on rods which passed through
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#17329172753631272-541: A large fireworks display is scheduled there as part of London's Bonfire Night celebrations. The Observer ' s Wildlife Exhibition held here in 1963 was an important early event in highlighting awareness of worldwide endangered species, and it gained a large attendance (46,000). In April 1967, a benefit event took place at the Palace. The 14 Hour Technicolor Dream , organised by the International Times , demonstrated
1378-689: A leading British electronics firm of the time, had pioneered television receiver design, and in the late 1930s, wanted to market receivers that would allow reception further and further from the single Alexandra Palace television transmitter. In particular, they wanted to be able to receive these transmissions at their Cambridge factories. They initially turned to their subsidiaries, Cathodeon and Hi-Vac, but they were not capable of producing much of an improvement. They turned to Mullard , who turned to their Philips managers in Eindhoven . With some tweaking from Baden John Edwards and Donald Jackson from Pye (for example
1484-480: A link to a clear, high-quality picture. Some subminiature tubes with flexible wire leads all exiting in the same plane were connected by subminiature inline sockets. Some low-power reflex klystrons such as the 2K25 and 2K45 had small-diameter rigid coaxial outputs parallel to octal base pins. To accommodate the coax, one contact was replaced by a clearance hole. Vacuum tubes for high-power applications often required custom socket designs. A jumbo four-prong socket
1590-687: A metal button at the top of the tube rather than the bottom, but this made construction much more complex, as well as making connections in radio sets more difficult as they could no longer be on a single circuit board . Through the early 1930s, a number of companies experimented with metal tubes, using a variety of sealing methods. These worked well, but tended to be rather large and were never able to be successfully mass-produced at low cost. RCA continued experiments with all-glass tubes and introduced their "acorn" (or "door knob") tubes late in 1934. These were essentially two half-tubes that were assembled separately, carefully folded together, and then sealed along
1696-666: A new design by architect E.T. Spashett during renovation of bomb-damaged public buildings by the Ministry of Works . During the 1940s and 1950s the Palace also housed a public roller-skating rink and the Alexandra Palace Roller Skating Club . In the early 1960s, an outside broadcast was made from the top of the tower, in which the first passage of a satellite across the London sky was watched and described. It continued to be used for BBC News broadcasts until 1969, and for
1802-545: A new transit connection—either a monorail line or a branch of the Piccadilly line —and private funding. The proposal was rejected by the GLC after local opposition cited the potential for hooliganism in the area. Early in 1980, Haringey council took over the trusteeship of Alexandra Palace from the GLC, insuring it for £31 million, intending to refurbish the building but just six months later, during Capital Radio 's Jazz Festival,
1908-458: A number of prongs ranging from three to seven, with either a non-regular distribution or with one or two of the prongs of bigger diameter than the other, so that the tube could only be inserted in a certain position. Sometimes they relied on a bayonet on the side of the base. Examples of these are the very common USA bases UX4, UV4, UY5 and UX6, and the European B5, B6, B7, B8, C7, G8A, etc. Tubes in
2014-460: A receiver that was small and light enough to be used on aircraft. Their original design was based on a television chassis from EMI using RCA acorn valves. Only one set was available and almost lost in an accident, so Bowen was eager to find additional receivers. When the war began in the summer of 1939, all work on civilian television was suspended. This left Pye with many completed chassis and no way to sell them. Edward Victor Appleton , who had been
2120-745: A recording of portions of all three shows was released as part of the Dick's Picks series in March 1997. The Campaign for Real Ale held the Great British Beer Festival there from 1977 to 1980 (the 1980 edition taking place in tents outside the fire-damaged Alexandra Palace ). On the afternoon of 10 July 1980 (an accidental) fire destroyed the Great Hall, Banqueting Suite, Dressing Rooms and Ice Rink during contractors routine repairs and maintenance. From 27 July to 5 August 1973, The London Music Festival '73
2226-596: A simpler device where useful, as in the four connections to the grid of a conventional grounded-grid UHF triode, e.g. , 6AM4, to minimise the deleterious effects of lead inductance on the high-frequency performance. This base type was used by many of the United States and most of the European tubes, e.g. , 12AX7 -ECC83, EF86 and EL84 , produced commercially towards the end of the era before transistors largely displaced their use. The IEC 67-I-12a specification calls for
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#17329172753632332-464: A useful reduction in physical size compared to previous common types, such as octal (especially important in TV receivers where space was limited), while also providing a sufficient number of connections (unlike B7G) to allow effectively unrestricted access to all the electrodes, even of relatively complex tubes such as double triodes and triode-hexodes. It could also provide multiple connections to an electrode of
2438-414: A way to weld the tube into the base plate instead of the top of the tube, but this left the tube projecting from the bottom, where it could be easily snapped off. The solution to this was a metal shell that was fit onto the bottom of the tube at the end of construction, covering the evacuation tube while allowing the connection pins to project through holes. This was known as "the metal trouser". Pye Ltd. ,
2544-662: A £27m refurbishment of the long-abandoned Alexandra Palace theatre and east wing. In 2018, it was announced that the Theatre would open for a BBC Proms performance on 1 September before officially reopening to the public on 1 December 2018 following the completion of the East Wing Restoration Project by the contractor Willmott Dixon . The opening programme included performances from Dylan Moran , Horrible Histories , Gilbert & George , Gareth Malone and an evening of jazz presented by Ronnie Scott's . During
2650-555: Is alluded to by the rays in the modern coat of arms of the London Borough of Haringey . Two competing systems, Marconi-EMI's 405-line system and John Logie Baird 's 240-line system, were installed, each with its own broadcast studio and were transmitted on alternate weeks until the 405-line system was chosen in 1937. After the BBC leased the eastern part of the Palace the theatre was only used for props storage space. The Palace continued as
2756-596: Is an entertainment and sports venue in North London, situated between Wood Green and Muswell Hill in the London Borough of Haringey . A Grade II listed building, it is built on the site of Tottenham Wood and the later Tottenham Wood Farm. Originally built by John Johnson and Alfred Meeson , it opened in 1873 but following a fire two weeks after its opening, was rebuilt by Johnson. Intended as "The People's Palace" and often referred to as " Ally Pally ", its purpose
2862-402: Is basically a nine-pin socket with an added center contact). As with loctal tubes, the pins of miniature tube are stiff wires protruding through the bottom of the glass envelope which plug directly into the socket. However, unlike all their predecessors, miniature tubes are not fitted with separate bases; the base is an integral part of the glass envelope. The pinched-off air evacuation nub is at
2968-628: Is the Peanut 215, which instead of using prongs had a tiny bayonet base with four drop-like contacts. Another exception is the European Side Contact series commonly known as P, which instead of using a prong, relied on side contacts at 90 degrees from the tube axis with four to twelve contacts. In April 1935, the General Electric Company introduced a new eight-pin tube base with their new metal envelope tubes. The new base became known as
3074-639: The Ampex MR-70, a costly studio tape recorder whose entire electronics section was based on nuvistors. There are many other socket types, of which a few are: A remarkably wide variety of tube and similar sockets is listed and described, with some informal application notes, at a commercial site, Pacific T.V., including nuvistor, eight-pin subminiature, vidicon, reflex klystron, nine-pin octal-like, 10-pin miniature (two types), 11-pin sub-magnal, diheptal 14-pin, and many display tubes such as Nixies and vacuum fluorescent types (and even more). As well, each socket has
3180-581: The Edgware, Highgate and London Railway to connect the site to Highgate station . Work on both the railway and the Palace was completed in 1873 and, on 24 May of that year, Alexandra Palace and Park was opened. The structure covers some 7.5 acres (3.0 ha). The Palace was built by Kelk and Lucas , who also built the Royal Albert Hall in South Kensington at around the same time. Sims Reeves sang on
3286-865: The Harringay Racers , the Haringey Greyhounds , the London Racers and now the Haringey Huskies , as well as a figure skating club, the Alexandra Palace Amateur Ice Skating Club. In June 2004, the first performances for about 70 years took place in the theatre, first in its foyer then in July in the theatre itself. Although conditions were far from ideal, the audience was able to see the potential of this very large space – originally seating 3,000, it could not be licensed for more than
EF50 - Misplaced Pages Continue
3392-635: The Open University until 1981. The antenna mast still stands and is used for local terrestrial television transmission, local commercial radio and DAB broadcasts. The main London television transmitter is now at Crystal Palace in south London. The GLC considered a £20 million proposal in 1977 to redevelop the Alexandra Palace grounds into a multi-sport complex constructed around a shared football ground for North London clubs Arsenal and Tottenham Hotspur . The 75,000-seat stadium would have required
3498-538: The Piccadilly line . Alexandra Palace is also served by London Buses route W3. The "Palace of the People" was conceived by Owen Jones in 1859. The Great Northern Palace Company had been established by 1860, but was initially unable to raise financing for the construction of the Palace. Construction materials were acquired and recycled from the large 1862 International Exhibition building in South Kensington after it
3604-612: The coronavirus pandemic , Alexandra Palace was used as a food distribution hub by Edible London for local residents. Alexandra Palace has hosted a number of significant events. Recurring events held there include the Great British Beer Festival (1977–1980), the Brit Awards (1993–1995), the PDC World Darts Championship (2008–present) and the Masters snooker tournament (2012–2020 and 2022–2024). In November every year,
3710-519: The home of the BBC's first regular public television service. The broadcasting system was 405-line monochrome analogue television – the first fully electronic television system to be used in regular broadcasting. Although other facilities soon superseded it after the Second World War , Alexandra Palace continued to be used by the BBC for many years and its radio and television mast is still in use. The original studios 'A' and 'B' still survive in
3816-497: The octal base . The octal base provided one more conductor with a smaller overall size of the base than the previous line of U. S. tube bases which had provided a maximum of seven conductors. Octal bases, as defined in IEC 60067, diagram IEC 67-I-5a, have a 45-degree angle between pins, which form a 17.45 mm ( 11 ⁄ 16 in) diameter circle around a 7.82 mm ( 5 ⁄ 16 in) diameter keyed post (sometimes called
3922-410: The "missing" pin position being used to position the tube in its socket (unlike octal, loctal and rimlock sockets). Examples include the 6AQ5/EL90 and 6BE6/EK90. European tubes of this type have numbers 90-99, 100-109, 190-199, 900-999. A few in the 100-109 series have unusual, non-B7G bases, e.g. , Wehrmacht base. The nine-pin miniature Noval B9A base, sometimes called button 9-pin, B9-1, offered
4028-414: The 6A7 pentagrid converter . Later, some tubes, particularly those used as radio frequency (RF) power amplifiers or horizontal deflection amplifiers in TV sets, such as the 6DQ6, had the plate or anode lead protrude through the envelope. In both cases this allowed the tube's output circuitry to be isolated from the input (grid) circuit more effectively. In the case of the tubes with the plate brought out to
4134-565: The 6J6 ECC91 VHF dual triode, were introduced in 1939. The bases commonly referred to as "miniature" are the seven-pin B7G type, and the slightly later nine-pin B9A (Noval). The pins are arranged evenly in a circle of eight or ten evenly spaced positions, with one pin omitted; this allows the tube to be inserted in only one orientation. Keying by omitting a pin is also used in 8- (subminiature), 10-, and 12-pin ( Compactron ) tubes (a variant 10-pin form, "Noval+1",
4240-487: The BBC's main transmitting centre for London until 1956, interrupted only by the Second World War when the transmitter found an alternative use jamming German bombers' navigation systems . In 1944, a German doodlebug exploded just outside the organ end of the Great Hall and the Rose Window was blown in, leaving the organ exposed to the elements. In 1947 some of the pieces of the shattered rose window were incorporated in
4346-520: The Charity Commission's order authorising a 125-year lease of the entire building to Firoka Ltd. In September 2009, Alexandra Palace main hall was allowed 2,000 more occupation, up to 10,250 ("still saddled by a £37 million debt it owes its guardian, Haringey Council"). A masterplan for the future of the site was drawn up in 2012, comprising six 'big ideas' to restore and redevelop the Palace. The first of these to be implemented aims to transform
EF50 - Misplaced Pages Continue
4452-590: The EF50 had to come from Holland, yet was vital for the RDF ( radar ), great efforts were made to secure a continuing supply as the risk of Holland being overrun increased. Mullard in England did not have the ability to manufacture the special glass base, for example. Just before Germany invaded Holland, a truckload of 25,000 complete EF50s and many more of their special bases were successfully sent to England. The entire EF50 production line
4558-524: The EF50 include: The tube was also assigned the GPO ( PO ) VT-207 type number, VT-250, and CV1578. Valves of similar characteristics were produced with different bases, for example, the later EF42 and 9-pin miniature (B9A) EF80. Mullard EF50 data sheet Tube socket#Other Loctals Tube sockets are electrical sockets into which vacuum tubes (electronic valves) can be plugged, holding them in place and providing terminals, which can be soldered into
4664-674: The EF50 was also made by Marconi-Osram (with the name Z90) and Cossor (their version named 63SPT) in the United Kingdom as well as Mullard (who were effectively using the Philips production line after it was moved from Holland). Versions were also made in Canada by Rogers Vacuum Tube Company and in the United States by Sylvania Electric Products . British military (Ministry of Aircraft Production Specification) and U.S. JAN type numbers assigned to
4770-531: The Hornsey Historical Society. A planned commercial development of the building into a mixed leisure complex including a hotel, replacement ice-skating rink, cinema, ten-pin bowling alley and exhibition centre, encountered opposition from public groups and was blocked by the High Court in 2007. The Great Hall and West Hall are typically used for exhibitions, music concerts, and conferences, operated by
4876-408: The Palace was repaired immediately but Haringey council overspent on the restoration, creating a £30 million deficit. It was then reopened to the public in 1988 under a new management team headed by Louis Bizat. Later the council was heavily criticised for the overspend in a report by Project Management International. In 1991, the attorney-general stated that the overspending by the council as trustee
4982-433: The People"; it and its park were renamed to honour the popular new Princess of Wales, Alexandra of Denmark , who had married Prince Albert Edward on 10 March 1863. The Palace of the People, or the People's Palace, remained as alternative names. In September 1865, construction commenced but to a design by John Johnson and Alfred Meeson rather than the glass structure initially proposed by Jones. In 1871, work started on
5088-727: The Stone Roses performed a concert at Alexandra Palace. Hugh Cornwell played his last performance with the Stranglers at Alexandra Palace in August 1990. This was documented by the Saturday Night, Sunday Morning album and video. Blur performed a major concert at the venue in October 1994 to promote their album Parklife . The recording of the concert was released on video in February 1995 with
5194-501: The USA typically had from four to seven pins in a circular array, with adjacent pairs of larger pins for heater connections. Before alternating current (AC) line/mains-powered radios were developed, some four-pin tubes (in particular, the very common UX-201A ('01A)) had a bayonet pin on the side of a cylindrical base. The socket used that pin for retaining the tube; insertion finished with a slight clockwise turn. Leaf springs, essentially all in
5300-414: The absence of the skirt. In the European naming scheme, rimlock tubes are numbered in the ranges 40-49, 110-119 (with exceptions), and 400-499, e.g. , EF40. Although virtually unknown elsewhere, this was a very common base type in European radios of the late 1940s through the 1950s, but was eventually displaced by the ubiquitous B7G and Noval (B9A) base types. By 1935 new tube technologies were required for
5406-440: The brick infills in the colonnade on the south-east face of the building, which the BBC constructed after 1936 to form their television studios within. Following a public consultation and advice from English Heritage, Planning and Listed Building Consent was given for the proposals and in March 2015 HLF awarded Round 2 major grant funding securing a positive future for the historic areas. In 2018, Feilden Clegg Bradley Studios made
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#17329172753635512-418: The centerline. Despite using low-cost materials and construction, the manual assembly led to high costs. In Germany, Telefunken introduced the "Stahlröhre" (~steel tube) with its own issues. Philips had been working from 1934 to 1935 on an alternative that would solve the problems of the other base designs, in a system that could be produced cheaply and in large quantities. A presentation by M.J.O. Strutt from
5618-467: The circuit, for each of the pins. Sockets are designed to allow tubes to be inserted in only one orientation. They were used in most tube electronic equipment to allow easy removal and replacement. When tube equipment was common, retailers such as drug stores had vacuum tube testers , and sold replacement tubes. Some Nixie tubes were also designed to use sockets. Throughout the tube era, as technology developed, sometimes differently in different parts of
5724-576: The derelict eastern end of the Palace, making accessible the Victorian theatre and historic BBC Studios. In 2013 the Heritage Lottery Fund awarded a Round 1 pass to develop the proposals, creating a new entrance in the restored East Court, re-establishing the theatre as a flexible performance space and re-opening the BBC Studios as a visitor attraction. There was controversy regarding plans to demolish
5830-489: The development of radar and telecommunications. UHF requirements severely limited the existing tubes, so radical ideas were implemented which affected how these tubes connected to the host system. Two new bases appeared, the acorn tube and the lighthouse tube, both solving the same problems but with different approaches. Thompson, G.M. Rose, Saltzberg and Burnside from RCA created the acorn tube by using far smaller electrodes, with radial short connections. A different approach
5936-553: The district, headed by Mr. Henry Burt JP , a member of the Middlesex County Council and of Hornsey District Council, at once embraced the opportunity of securing the Palace and the beautiful grounds for the people of London. A committee was formed by Burt and the consortium managed to raise enough money to purchase them just in time. By the Alexandra Park and Palace (Public Purposes) Act 1900 ( 63 & 64 Vict. c. cclix),
6042-678: The first radio using these miniature tubes, the "Candid", in April 1940. In June 1940 RCA released its battery-operated Model BP-10 , the first superheterodyne receiver small enough to fit in a handbag or coat pocket. This model had the following tube lineup: 1R5 — pentagrid converter ; 1T4 — I.F. amplifier ; 1S5 — Detector /AVC/AF Amplifier; 1S4 — Audio Output. The BP-10 proved so popular that Zenith, Motorola, Emerson, and other radio manufacturers produced similar pocket radios based on RCA's miniature tubes. Several of these pocket radios were introduced in 1941 and sold until
6148-489: The funeral service of the Labour MP Bernie Grant took place at the Palace. An estimated 3,000 people attended. The fourth Mind Sports Olympiad was held at Alexandra Palace in August 2000, with more than 4,000 competitors from around the world taking part in mind sports. In December 2002, The Miss World 2002 pageant was staged at the venue. In June 2007, a Hackday event was hosted at Alexandra Palace by
6254-417: The general manager, W. J. MacQueen-Pope , spending the war reparation money on refurbishing the auditorium. He abandoned the understage machinery that produced the effects necessary in Victorian melodrama; some of the machinery is preserved, and there is a project to restore some of it to working order. After these changes, the theatre was leased by Archie Pitt , then husband of Gracie Fields , who appeared in
6360-481: The grounds (in the middle of the old racecourse) since 1888. A Henry Willis organ installed in 1875, vandalised in 1918 and restored and reopened in 1929, survives. In its 1929 restored form, Willis's masterpiece was declared by Marcel Dupré to be the finest concert organ in Europe. In 1900, the owners of Alexandra Palace and Park were threatening to sell them for redevelopment, but a consortium of public-spirited men in
6466-788: The heater, and flying leads for the other elements. Other tubes directly used flying leads for all of their contacts, like the Cunningham AudioTron from 1915, or the Deforest Oscillion . Type C6A xenon thyratrons , used in servos for the U.S. Navy Stable Element Mark 6 , had a mogul screw base and L-shaped stiff wires at the top for grid and anode connections. Mating connectors were machined pairs of brass blocks with clamping screws, attached to flying leads (free hanging). When tubes became more widespread, and new electrodes were added, more connections were required. Specially designed bases were created to account for this need. However, as
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#17329172753636572-416: The hollow base pins, where they were soldered to make permanent connections. Loctal tubes had shorter connecting lengths between the socket pins and the internal elements than did their octal counterparts. This allowed them to operate at higher frequencies than octal tubes. The advent of miniature "all-glass" seven- and nine-pin tubes overtook both octals and loctals, so the loctal's higher-frequency potential
6678-654: The importance of the quickly developing Underground scene. Although venues such as the UFO Club were hosting counter-cultural bands, this was certainly the largest indoor event at the time. Performers included headlining act Pink Floyd as well as the Pretty Things , Savoy Brown , the Crazy World of Arthur Brown , Soft Machine , The Purple Gang , The Move and Sam Gopal's Dream (featuring Sam Gopal, Mick Hutchinson and Pete Sears ). John Lennon attended, and Yoko Ono (who
6784-452: The metal shield), the final EF50 pentode was produced and used in Pye's 45 MHz TRF design, and created a receiver able to receive transmissions at up to five times the distance than the competition. While Pye was working on their television systems, the top secret work on radar was being carried out at Bawdsey Manor . As part of this research, a team under Edward George Bowen was developing
6890-416: The mid-thirties) was the originator of the EF50. This development started as early as 1934–1935. It was, indeed, developed in view of possible television application." Their first attempts faced problems due to the mechanical loads of the connection pins. If they used leads that were strong enough to be pushed into a conventional socket, these were large enough that the holes in the glass plate greatly reduced
6996-565: The miniature tube pins (usually Cunife or Fernico ) and the tube base could cause intermittent contact due to local corrosion, especially in relatively low current tubes, such as were used in battery-operated radio sets. Malfunctioning equipment with miniature tubes can sometimes be brought back to life by removing and reinserting the tubes, disturbing the insulating layer of corrosion. Miniature tubes were widely manufactured for military use during World War II, and also used in consumer equipment. The Sonora Radio and Television Corporation produced
7102-582: The octal base for their pinout. A variant of the octal base, the B8G loctal base or lock-in base (sometimes spelled "loktal" — trademarked by Sylvania), was developed by Sylvania for ruggedized applications such as automobile radios. Along with B8B (a British designation out of date by 1958), these eight-pin locking bases are almost identical and the names usually taken as interchangeable (although there are some minor differences in specifications, such as spigot material and spigot taper, etc.). The pin geometry
7208-427: The opening day before an audience of 102,000. Only 16 days later, Alexandra Palace was destroyed by a fire which also killed three members of staff. Only the outer walls survived; a loan exhibition of a collection of English pottery and porcelain, comprising some 4,700 items of historic and intrinsic value, was also destroyed. The Palace was quickly rebuilt and reopened on 1 May 1875. The new Alexandra Palace contained
7314-450: The paralleled heaters. The octal base soon caught on for glass tubes, where the large central post could also house and protect the " evacuation tip " of the glass tube. The eight available pins allowed more complex tubes than before, such as dual triodes, to be constructed. The glass envelope of an octal base tube was cemented into a bakelite or plastic base with a hollow post in the center, surrounded by eight metal pins. The wire leads from
7420-418: The pinch. As tubes grew in complexity, the number of leads also grew. Since light bulb sizes were standardized, all of these had to pass through the same pinch, which placed them increasingly close to each other. This led to increased capacitance , which limited the tube's ability to work at high frequencies. To address this, to some degree at least, it became somewhat common to attach the control grid leads to
7526-455: The pins locked into place. With this problem solved, the team then turned to consider whether the top control grid connection could be eliminated, as it had been in the RCA acorns. This was easy enough to do electrically, but Philips had already taken to using the metal cap on the electrode as a convenient place to hide the gas evacuation tube, used during the final steps of construction. They developed
7632-444: The plate's physical strength, and cracking was a serious problem. Thinner wires would solve this problem, but these proved difficult to connect to in the socket, and the tubes tended to disconnect when jolted. The solution was to use bent pins, which exited the bottom of the tube and were then bent through a 90 degree arc toward the center of the tube's base. These were used with a special socket; when pressed in and rotated slightly,
7738-453: The printed wiring tracks. Looking at the bottom of a socket, or, equivalently, a tube from its bottom, the pins were numbered clockwise, starting at an index notch or gap, a convention that has persisted into the integrated circuit era. In the 1930s, tubes often had the connection to the control grid brought out through a metal top cap on the top of the tube. This was connected by using a clip with an attached wire lead. An example would be
7844-480: The range: Efforts to introduce small tubes into the marketplace date from the 1920s, when experimenters and hobbyists made radios with so-called peanut tubes like the Peanut 215 mentioned above. Because of the primitive manufacturing techniques of the time, these tubes were too unreliable for commercial use. RCA announced new miniature tubes in Electronics magazine, which proved reliable. The first ones, such as
7950-509: The same plane, pressed upward on the bottoms of the pins, also keeping the bayonet pin engaged. The first hot-cathode CRT, the Western Electric 224-B, had a standard four-pin bayonet base, and the bayonet pin was a live connection. (Five effective pins: It was an electrostatic-deflection gas-focused type, with a diode gun and single-ended deflection. The anode and the other two plates were common.) An early exception to these types of bases
8056-434: The socket contact. The loctal tube's structure was supported directly by the connecting pins passing through the glass "button" base. Octal tube structures were supported on a glass "pinch", formed by heating the bottom of the envelope to fusing temperature, then squeezing the pinch closed. Sealing the pinch embedded the connecting wires in the pinch's glass and gave a vacuum-tight seal. The connecting wires then passed through
8162-430: The socket wall. This provides pin registration (since the pins are equi-spaced) and also a fair degree of retention. Early tubes with this base type typically had a metal skirt around the lower ~15mm of the envelope to match the socket wall, and this offered a degree of built-in screening, but these were fairly soon replaced by "skirtless" versions, which had a characteristic widening in the glass to compensate physically for
8268-404: The southeast wing with their producers' galleries and are used for exhibiting original historical television equipment. The original Victorian Alexandra Palace Theatre with its stage machinery also survives and as of 2019, is back in use. The theatre and stage structure is on English Heritage 's Buildings at Risk register. Alexandra Palace became a listed building in 1996, at the instigation of
8374-498: The surrounding park; it is long since closed and little trace remains except some reeds. The grounds included a horse racing course with grandstand (named Alexandra Park Racecourse and nicknamed the "Frying Pan" and the "Pan Handle" because of its layout), which was London's only racecourse from 1868 until its closure in 1970, a Japanese village, a switchback ride, a boating lake and a 9-hole pitch-and-putt golf course . Alexandra Park cricket and football clubs have also played within
8480-440: The suspension of radio production in April 1942 for the duration of World War II. After the war miniature tubes continued to be manufactured for civilian use, regardless of any technical advantage, as they were cheaper than octals and loctals. The B7G (or " small-button " or " heptal ") seven-pin miniature tubes are smaller than Noval, with seven pins arranged at 45-degree spacing in a 9.53 mm (3/8th inch) diameter arc,
8586-405: The team had already selected 200 MHz as the basic operational frequency. Like the earlier EMI model, the Pye receiver was then adapted from the BBC 45 MHz standard to 200 MHz by adding a single step-down stage in front of an otherwise unmodified Pye chassis. The resulting "Pye strip" became the basis for many UK radar designs of the era, including AI Mk. IV and ASV Mk. II . Because
8692-621: The theatre. Fields also drew an audience of 5,000 people to the hall for a charity event. In 1935, the trustees leased part of the Palace to the BBC for use as the production and transmission centre for their new BBC Television service. The antenna was designed by Charles Samuel Franklin of the Marconi Company . The world's first public broadcasts of (then) "high-definition" television were made from Alexandra Palace in November 1936, an event which
8798-487: The thesis advisor for both Bowen and Harold Pye , mentioned these surplus chassis to Bowen and suggested he try them. Bowen contacted Pye and found that "scores and scores" of completed chassis were available. When tested, they were found to completely outperform the EMI model. Operational requirements, mostly the size of the dipole antennas suitable for external mounting on an aircraft, demanded that short wavelengths be used, and
8904-486: The title Showtime and used as the basis for the video for the band's song " End of a Century ". From 1993 to 1995, the Brit Awards were hosted at Alexandra Palace. In November 1996 it was the venue for the annual MTV Europe Music Awards . In 1996, the Palace hosted the inaugural London Model Engineering Exhibition which continued each year until 2021 when it was cancelled due to the COVID-19 pandemic . In April 2000,
9010-469: The top of the tube, giving it its distinctive appearance. More than one functional section can be included in a single envelope; a dual triode configuration is particularly common. Seven- and nine-pin tubes were common, though miniature tubes with more pins, such as the Compactron series, were later introduced, and could fit up to three amplifying elements. Some miniature tube sockets had a skirt that mated with
9116-541: The trading arm of the charitable trust that owns the building and park on behalf of the public. There is also a pub, ice rink , palm court , and a panoramic view of central London. In 2013, Alexandra Park was declared a local nature reserve and is also a Site of Borough Importance for Nature Conservation , Grade 1. The nearest railway stations are the Alexandra Palace with Great Northern services from Moorgate and London Underground station Wood Green on
9222-470: The trustees to maintain the building and park and make them available for the free use and recreation of the public forever. The present trustee is the London Borough of Haringey, whose coat of arms shows lightning bolts depicting Alexandra Palace's pioneering role in the development of television. In 1935, the trustees leased part of the Palace to the BBC for use as the production and transmission centre for their new television service . In 1936, it became
9328-710: The tube development group at Philips Research at the first "Internationale Fernseh-Tagung in Zürich" (international television conference in Zürich) described their work in September 1938. A few months later, Professor J.L.H. Jonker, who had a leading role in the development of the EF50, published an internal Philips Research Technical Note, Titled: "New radio Tube Constructions". Jonker's role was confirmed decades later by Th. P. Tromp, head of radio-valve manufacturing and production: "Prof. Dr. Jonker (head of development lab of electronic valves in
9434-455: The tube were soldered into the pins, and the evacuation tip was protected inside the post. Matching plugs were also manufactured that let tube sockets be used as eight-pin electrical connectors ; bases from discarded tubes could be salvaged for this purpose. Octal sockets were used to mount other components, particularly electrolytic capacitor assemblies and electrical relays ; octal-mount relays are still common. Most octal tubes following
9540-474: The tubes in many table radios. Loctal tubes have a small indexing mark on the side of the base skirt; they do not release easily from their sockets unless pushed from that side. Because the pins are actually the Fernico or Cunife lead-out wires from the tube, they are prone to intermittent connections caused by the build-up of electrolytic corrosion products due to the pin being of a different metallic composition to
9646-594: The two-hour-long gig and were uniquely made available from specific Harlequin Record Shops within Central London. In 1973, the Divine Light Mission held a "Festival of Love" there. Also in 1973, British rock band Wishbone Ash played a Christmas concert at the Palace, billed as "Christmas at the Palace". The American band Grateful Dead played a series of three shows there between 9 and 11 September 1974;
9752-532: The widespread European designation system have penultimate digit "3" as in ECC34 (full details in the Mullard–Philips tube designation article). There is a different, totally obsolete, pre-world-war-II German octal type. Octal and miniature tubes are still in use in tube-type audio hi-fi and guitar amplifiers . Relays were historically manufactured in a vacuum tube form, and industrial-grade relays continue to use
9858-421: The world was suffering from World War I , and the new electronics technology was just emerging, designs were far from being standardized. Usually, each company had their own tubes and sockets, which were not interchangeable with tubes from other companies. By the early 1920s, this situation was finally changing, and several standard bases were created. They consisted of a base (ceramic, metal, bakelite , etc.) with
9964-500: The world, many tube bases and sockets came into use. Sockets are not universal; different tubes may fit mechanically into the same socket, though they may not work properly and possibly become damaged. Tube sockets were typically mounted in holes on a sheet metal chassis and wires or other components were hand soldered to lugs on the underside of the socket. In the 1950s, printed circuit boards were introduced and tube sockets were developed whose contacts could be soldered directly to
10070-466: Was cancelled due to higher-than-anticipated costs. Plans by the current trustees, Haringey Council, to replace all the charitable uses by commercial ones by a commercial lease of the entire building, including a casino, encountered considerable public and legal opposition, and on 5 October 2007, in the High Court, Mr. Justice Sullivan granted an application by Jacob O'Callaghan, a London resident, to quash
10176-462: Was demolished: the Government had declined to take it over. In 1863 Alexandra Park Co. Ltd. acquired the land of Tottenham Wood Farm for conversion to a park and to build the People's Palace, on a site that stands on a ridge more than 300 ft (91 m) high, part of Muswell Hill . Alexandra Park was opened to the public on 23 July 1863. The planned building was originally named "The Palace of
10282-540: Was held here. After the fire, the burnt-out shell of the great hall of Alexandra Palace was used as Victory Square in Michael Radford 's 1984 film adaptation of George Orwell 's novel Nineteen Eighty-Four . The Sinclair C5 battery electric vehicle was launched at the Palace in January 1985, one week after the closure of the 405-line television system that was inaugurated there 49 years earlier. In November 1989,
10388-564: Was hurriedly relocated to Britain. On 13 May, the day before the Germans flattened Rotterdam in 1940, members of the Philips family escaped together with the Dutch government on the British destroyer HMS Windsor , taking with them a small wooden box containing the industrial diamonds that were to be used to make the dies needed to make the fine tungsten wires in the valves. To meet great wartime demand,
10494-477: Was never fully exploited. Loctal tube type numbers in the USA typically begin with "7" (for 6.3-volt types) or "14" for 12.6-volt types. This was fudged by specifying the heater voltage as nominally 7 or 14 volts so that the tube nomenclature fitted. Battery types (mostly 1.4-volt) are coded "1Lxn", where x is a letter and "n" a number, such as "1LA4". Russian loctals end in L, e.g. 6J1L. European designations are ambiguous; all B8G loctals have numbers either in
10600-459: Was soon to become Lennon's new romantic partner) presented her performance work "Cut Piece". In 1970, Italian director Lucio Fulci filmed an important segment of his giallo film A Lizard in a Woman's Skin here. Alexandra Palace posed as a disused church. The rock band Led Zeppelin played at Alexandra Palace's Grand Hall in two sell out performances on the evenings of the 22/23 December 1972. Their concert tickets were priced at £1 each for
10706-515: Was taken by the designers of the lighthouse tube, such as the octal-base 2C43 , which relied on using concentric cylindrical metal contacts in connections that minimized inductance, thus allowing a much higher frequency. Nuvistors were very small, reducing stray capacitances and lead inductances. The base and socket were so compact that they were widely used in UHF TV tuners. They could also be used in small-signal applications at lower frequencies, as in
10812-402: Was the same as for octal, but the pins were thinner (although they will fit into a standard octal socket, they wobble and do not make good contact), the base shell was made of aluminium, and the center hole had an electrical contact that also mechanically locked (hence "loctal") the tube in place. Loctal tubes were only used widely by a few equipment manufacturers, most notably Philco , which used
10918-516: Was to serve as a public centre of recreation, education and entertainment; North London 's counterpart to the Crystal Palace in South London . At first a private venture, in 1900, the owners planned to sell it and Alexandra Park for development. A group of neighbouring local authorities managed to acquire it. An Act of Parliament created the Alexandra Palace and Park Trust. The Act required
11024-516: Was transferred to Haringey council in 1980. During the First World War the park was closed; the Palace and grounds were firstly used as a refugee camp for displaced Belgians, and then later from 1915 to 1919 as an internment camp for German and Austrian civilians. The camp commandant was Lt. Col. R. S. F. Walker until his death in May 1917. The theatre was greatly altered in the early 1920s, with
11130-524: Was unlawful, and so could not be charged to the charity. The council for some years did not accept this politically embarrassing finding and instead maintained that the charity "owed" the council £30 million, charged compound interest on what it termed a "debt" (which eventually rose to a claim of some £60 million), and to recoup it tried to offer the whole palace for sale. An ice rink was installed at Alexandra Palace in 1990. Primarily intended for public skating, it has also housed ice hockey teams including
11236-603: Was used for various industrial tubes. A specialized seven-pin socket (Septar or B7A), with all pins in a circle with one pin wider than the others, was used for transmitting tubes. Subminiature tubes with long wire leads, introduced in the 1950s, were often soldered directly to printed circuit boards. Sockets were made for early transistors , but quickly fell out of favor as transistor reliability became established. This also happened with early integrated circuits; IC sockets later became used only for devices that may need to be upgraded. Alexandra Palace Alexandra Palace
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