GB802982A - Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tube - Google Patents
Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tubeInfo
- Publication number
- GB802982A GB802982A GB1301255A GB1301255A GB802982A GB 802982 A GB802982 A GB 802982A GB 1301255 A GB1301255 A GB 1301255A GB 1301255 A GB1301255 A GB 1301255A GB 802982 A GB802982 A GB 802982A
- Authority
- GB
- United Kingdom
- Prior art keywords
- capacitor
- pulses
- valve
- line
- cut
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
- H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
- H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
- H04N3/20—Prevention of damage to cathode-ray tubes in the event of failure of scanning
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Details Of Television Scanning (AREA)
Abstract
802,982. Cathode-ray tube operating circuits. FERRANTI, Ltd. July 31, 1956 [May 5, 1955], No. 13012/55. Class 40 (7). The embodiment of a cathode-ray tube screen protection circuit includes a capacitor 28 between control grid of a projection-type television tube 30 and earth, the tube beam being cut off unless the capacitor carries a charge above a critical value. Positive-going line flyback pulses are applied at 12 and positive-going frame flyback pulses at 20. Assuming that valve 22 is biased to cut-off, the amplified line pulses at screen grid 15 positively charge capacitor 28 via capacitor 24 and brightness control 26, negative pulse peaks being removed by diode 25 (which may be a metal rectifier) and the long time-constant of components 26, 27, 28 affording integration of the charging pulses prevents unwanted modulation of the beam current. When the line time-base is running normally, capacitor 28 has a sustained positive charge sufficient to permit tube beam current to flow. At switching on, capacitor 28, until it is charged to above the critical value, will maintain the beam cut-off. The connection of capacitor 28 to the anode of valve 10 serves to rapidly discharge the capacitor when the line time-base fails and the receiver is in operation; the negative signal at suppressor grid 17 ensures that the anode of valve 10 is cut off from space current when the line time-base is operating normally. With no charging pulses to capacitor 28 the viewer cannot bring the beam on again by manipulation of brightness control 26. The effect of frame pulses is to produce intermittent conduction in valve 22, thus causing a momentary reduction of voltage across resistor 26 but the long-time constant of circuit 26 to 28 prohibits unwanted tube beam modulation. If there are no frame pulses at switching on, valve 22 conducts continuously and the resulting low potential of screen grid 15 prevents charging of capacitor 28 and the tube beam remains cut off; and similarly when the frame time-base fails in operation, in which case beam cut-off is less rapid than when line pulses fail since capacitor 28 takes longer to discharge through resistors 26, 27 than through valve 10. The circuit has certain features of inherent selfprotection and it is preferable for valve 22 to share the cathode of valve 10. The lower end of capacitor 28 may alternatively be connected to H.T. positive; the line and frame pulses may be derived by other than flyback means; and the capacitor may be charged directly by line pulses. Where the cathode-ray tube uses electrostatic deflection an extra stage may be provided to give suitable line pulses from the line time-base.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1301255A GB802982A (en) | 1955-05-05 | 1955-05-05 | Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tube |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1301255A GB802982A (en) | 1955-05-05 | 1955-05-05 | Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tube |
Publications (1)
Publication Number | Publication Date |
---|---|
GB802982A true GB802982A (en) | 1958-10-15 |
Family
ID=10015212
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB1301255A Expired GB802982A (en) | 1955-05-05 | 1955-05-05 | Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tube |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB802982A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2256778A (en) * | 1991-05-17 | 1992-12-16 | Thomson Consumer Electronics | Scan loss detector for a cathode ray tube |
-
1955
- 1955-05-05 GB GB1301255A patent/GB802982A/en not_active Expired
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2256778A (en) * | 1991-05-17 | 1992-12-16 | Thomson Consumer Electronics | Scan loss detector for a cathode ray tube |
GB2256778B (en) * | 1991-05-17 | 1996-01-03 | Thomson Consumer Electronics | Scan loss detector for cathode ray tube |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US2303924A (en) | Television transmitting or receiving system | |
GB546507A (en) | Cathode ray tube circuits | |
MY105388A (en) | A protection circuit for a cathode ray tube | |
GB402181A (en) | Improvements in or relating to television and the like systems | |
GB698296A (en) | Improvements in or relating to television receiver circuit arrangements | |
US2285043A (en) | Television receiver | |
US3629644A (en) | High-voltage regulation and protection circuit | |
GB1238771A (en) | ||
GB945145A (en) | Improvements relating to circuits for protecting the luminescent coatings of cathoderay tubes | |
US3379924A (en) | Television deflection circuits | |
GB802982A (en) | Improvements relating to apparatus for protecting the phosphor screen of a cathode-ray tube | |
US2442304A (en) | Pulse keying circuit | |
US2752525A (en) | Protection circuit for cathode ray tubes | |
US2774007A (en) | Beam cut-off circuit | |
US3407330A (en) | Protection circuit for cathode ray tube | |
GB1170137A (en) | Energizing Circuit for Degaussing Apparatus. | |
US2607018A (en) | Means and method for protecting kinescope screens | |
US2520155A (en) | Sweep circuit for cathode-ray tubes | |
GB740881A (en) | Improvements in or relating to television receivers | |
US2988594A (en) | Contrast control circuit | |
US2760108A (en) | Cathode ray tube blanking circuit | |
GB1059125A (en) | Improvements relating to circuits for protecting the luminescent coating of a cathode ray tube | |
GB798363A (en) | Improvements in or relating to colour-television receivers | |
US2912618A (en) | Circuit arrangement in radar receivers for controlling the deflection of the cathode-rays in cathode-ray tube indicators | |
GB968719A (en) | Improvements in control circuits of cathode ray tubes |