35Z5 GT

Description The 35Z5 is a half wave rectifier for heater chain service. The maximum reservoir capacitor is 40 μF and the surge limiting series resistance must be at least 100 Ohms.
The heater is tapped to allow a dial lamp to be wired in parallel with a portion of the heater. The lamp lasts longer as the surge is reduced and the radio continues to work with a broken dial lamp.The anode has a small front to back dimension.

Face on the anode is broad and the plates are fixed together by punching rectangular holes in one plate and pushing lugs formed in the other plate into the holes and then folding them over to lock them.
Manufacturer Hitachi
Country of Origin  Japan
Introduction Year 1939

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3SL6

 

Description The UCL82 triode pentode was designed for single ended audio output stages in universal mains domestic equipment, normally radios. In this application the output of 3 Watts was more than adequate for most rooms. For television use, with more valves in the chain, the 300 mA version the PCL82 would have been appropriate. The standard for AC mains sets using a mains transformer would have been the ECL82.
Manufacturer BEL
Country of Origin India

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6SK7

Description The 6SK7 is a variable μ pentode for RF and IF amplifiers in superhet receivers. The gain of the device being controlled by a negative voltage derived from rectifying the final IF signal. In this way strong signals do not overload the receive chain because the various controlled stages have their gain reduced.
The American Type designations such as 6SK7 refer to a single ended version of another Valve in this case the 6K7.
The 12SK7 had identical characteristics apart from the heater. The 12.6 Volt heater being used directly across a vehicle battery.
Manufacturer RCA, Kenard
Country of Origin  USA, USA
Introduction Year 1938

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El84

Description The EL84 output pentode was introduced by Mullard in 1954. To demonstrate its use and quality the Mullard applications lab produced an amplifier design. The now classic 5-10 high quality audio amplifier.
The EL84 has been very successful. With the renewal of interest in valve audio in the 21st century new manufacturing has been established in Europe and the far east. This exhibit is of Russian manufacture and branded as a Groove Tube. Rob says that a pair of these Sovtek EL84s were supplied in a Fender pro-junior amplifier.
When used as a pair in an ultra-linear push-pull configuration with 43% distributed loading the output could reach 10 W with 0.9 % total harmonic distortion. The valve operating conditions so produced were intermediate between a triode and a pentode. The operation of the distributed loading was to introduce negative feedback directly within the output stage.
Manufacturer  BEL, Tesla, Philips Miniwatt
Country of Origin  India,Czechoslovakia, Holland
Introduction Year 1948

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EM84

Description The EM84 tuning indicator, or magic eye, was used to display the optimum tuning point of a receiver, or the recording level of a tape recorder. The main benefit in reception was for FM radio where the exact tuning point was harder to determine than for AM.
This valve is in a standard thin glass tube envelope with a phosphor strip on the inside of the glass. The electrode structure is, like all such tuning indicators, based on a double triode with common cathode. The anode of the second triode is called the target and within the electron stream is a deflector electrode designed to alter the path of the electron beam, it would normally be connected to the anode. In the EM84 the quiescent condition was two green bars, one at each end of the window. As the signal strength increased the bars would elongate and eventually overlap to form a bright green region. The optimum point for tuning was a minimum gap.
The EM84 when used in domestic reel to reel tape recorders as a recording level indicator was adjusted so that the optimum recording level was set when the bars just overlapped on sound peaks.
The total column length change was 21 mm.
Other tuning indicators with end windows would have round displays with variable percentages of the circumference illuminated.
Mullard themselves styled the EM84 as a voltage indicator to denote the greater precision of build than was required for the simple task of a tuning indication where only the maxima was important.
Manufacturer BEL
Country of Origin INDIA
Introduction Year 1959

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UBF 89

Description The UBF89 is an RF or IF amplifier pentode with two diodes sharing the common cathode.
The screen blocks the main electrodes but through the hole in the screen the wire grids can be seen.
Manufacturer BEL
Country of Origin India
Introduction Year 1956

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6E5 – Magic Eye

Courtesy: Radio Museum

Courtesy: Radio Museum

Description The magic eye class of tuning indicator originated in the US and Type 6E5 was one of the earliest types to hit the market. Almost all European types are more-or-less directly copied from it.
Early specimens had short lives due to ‘burning’ of the fluorescent target and poisoning of the cathode coating in the centre of the target area. This was later cured by enclosing this part of the cathode within the spiral of a small space charge grid.
Early (pre-war) specimens lack this extra grid, later replacements have it. Our specimen looks fairly early, and well-used.
The display changes from open to closed for a 7.5 Volt change on the grid.
The end window envelope is 36 mm in diameter and, excluding the UX6 base pins, is 84 mm tall.
Manufacturer Sylvania
Country of Origin  USA
Introduction Year 1935

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ECH81

Description The ECH81 triode heptode was designed in 1954 for the role of frequency changer (mixer) in superhet receivers for AM reception. The ECH81 acting as oscillator and mixer for AM and the heptode being the first IF amplifier on FM.
The two valve sections share a common cathode. The triode is to be used as the local oscillator feeding the 13 Volts amplitude sine wave to the heptode mixer. Within the heptode, non linear operating causes the signals to interact to produce in the anode waveform the following major frequencies: signal, LO, signal + LO and signal minus LO. The anode circuit is tuned to enhance one of these signals, normally signal minus LO. For radio reception at the time an intermediate frequency of 455 KHz would be typical for AM.From the side, through the screen, can be seen two sizes of electrodes. Under a glass the lower section can be seen to contain several wire grid spirals. Above the main assembly the cathode continues and a single grid can be seen. Thus the triode is mounted above the mixer on the common cathode tube.
Manufacturer BEL
Country of Origin India

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UY85

Description The UY85 is a half wave rectifier and would be used on small universal (AC/DC) mains appliances. The heater chain would draw 100 mA and this was to enable the small number of valves used in a broadcast radio receiver to be run without a large dropper (ballast) resister.
The UY85 can work into a maximum reservoir capacitance of 100 µF, as protection a series resistance of 100 Ohms minimum is required.
Manufacturer BEL
Country of Origin India

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UCL 82

Description The UCL82 triode pentode was designed for single ended audio output stages in universal mains domestic equipment, normally radios. In this application the output of 3 Watts was more than adequate for most rooms. For television use, with more valves in the chain, the 300 mA version the PCL82 would have been appropriate. The standard for AC mains sets using a mains transformer would have been the ECL82.
Manufacturer BEL
Country of Origin India

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