GP-5 is a radio tube , high-voltage regulating triode . Used in the Soviet color TVs of the 701-710 generation (ULCT (I) ), produced from the beginning to the end of the 1970s. In the later versions of ULCT (models 711 and further) the use of GP-5 was discontinued due to the transition to a multiplier as a source of anode voltage.
The lamp is known as a very powerful source of x-ray radiation in household appliances, thanks to this property based on this lamp, it is possible to make sources of near-x-ray radiation.
Content
Description
This is a small radio tube ( EVP ), a triode with an anode contact brought to the top of the bulb of the lamp. Approximate dimensions: 120 mm in length and 45 mm in diameter.
The GP-5 is capable of withstanding anode voltage over 25 kV and dissipating power over 25-30 W, which according to the Soviet nomenclature transferred the lamp from a general-purpose discharge to a discharge generator . This explains the difference between the name "GP-5" from the usual Soviet nomenclature of lamps of the type Volta-Akkala-TipLampy-KodModeli-TipKorpusa .
Some options
The rated voltage at the anode is 30 kV (in the absence of heat up to 40 kV). The rated voltage is 6.3 V, the maximum allowable is 6.9 V. The anode current is 1.3 mA. Locking voltage on the grid is -20 V. Input resistance is 1 MΩ. Claimed durability - 1500 hours of work.
During operation, the GP-5 cylinder is heated to 250 ° C, which makes the lamp particularly fire hazardous; GP-5 was a common cause of the fire of tube TVs in the past.
Use
The first-generation output stage cascade circuit of ULCTT used a high-voltage boost winding and a kenotron to power the second anode of the kinescope . The masked three-beam kinescope required more voltage and current than a single-beam kinescope of a black-and-white TV with the same screen size, since about 80-85% of the electrons were retained by the mask. Large, compared to b / w kinescopes, the current of the rays (1000 μA against 180 μA), led to a noticeable voltage drop on the kenotron and the boost winding (large parasitic capacitances due to the large number of turns, etc.). In this case, changes in the average brightness of the image led to a change in the voltage of the second anode. In order to avoid this phenomenon, a parallel stabilizer was used, which is similar in principle to a parametric stabilizer on a semiconductor or gas-filled zener diode, with the difference that the triode could be controlled by changing the voltage on the grid [1] . This was used to correct the actual voltage value, which made it possible not only to keep the current consumed by the high-voltage circuits approximately constant, but also to compensate, for example, the deliberate changes in the amplitude necessary to correct the raster at the picture tube with a 90-degree deviation angle - the sawtooth current was modulated in parabolic the law.
The anode voltage control circuit and used the GP-5 lamp, the anode “cap” of which was connected to the anode terminal of the kinescope , and the cathode was grounded. By adjusting the voltage on the grid of the lamp, the current through it was regulated, and the sum of the currents through the kinescope and through the lamp was approximately constant, which kept the voltage constant.
Thus, the voltage on the lamp was equal to the anode (25 kV), and the current flowing through it was of the same order as the kinescope beam current, that is, about 1 mA when transmitting dark images. This led to the scattering of 25-30 watts on the lamp.
The output cascade for horizontal scanning of ULPCT was located on the right (as viewed from the back of the removed cover) side of the housing in a perforated case. The casing was divided into several compartments in which there were fuel assemblies with a kenotron, a damper diode lamp, an output key lamp, and the GP-5. GP-5 was located in a separate compartment of the casing.
Disadvantages
A heat source of 25–30 W (almost a desk lamp or a soldering iron) located at the top of the case greatly increased the fire hazard of the TV.
A vacuum device under a voltage of 25 kV inevitably begins to emit in the x-ray range. If the kinescope has a thick glass with lead content, then GP-5 did not have it, and, thus, was the source of x-ray radiation.
Despite the placement of the lamp in a separate screen, it was enough to expose a sealed stack of photo paper (there were prints of holes in the screen on paper).
In the case when GP-5 lost its emission (“sat down”), the adjustment of the anode voltage was lost and the voltage increased. This led to a narrowing of the size of the image and the need to adjust the scanning again, and, most importantly, could cause X-rays from the screen of the kinescope [2] .
Notes
- ↑ Elyashkevich S. A. Troubleshooting and setting up color TVs. - 2nd ed .. - Moscow : Energy, 1976. - p. 134. - 272 p. - (Mass radio library).
- ↑ Sotnikov S.K. Adjustment and repair of color television sets ULTSTP (I) -59 / 61-II. - 2nd ed .. - Moscow : Radio and communication, 1986. - P. 28. - 64 p. - (Mass radio library).