PHILIPS COLOUR PICTURE TUBES AND ASSEMBLIES SELECTION GUIDE 1985 1989

The PHILIPS CRT Selection Guide following this introduction provides a complete  list of all the preferred tube
types and assemblies that are currently available, together with quick-reference data for each tube type
and deflection unit. 

However, the Device Specifications sections only provide data for basic families of tube types and tube assemblies. 

At the front of each Device Specification section is a list of types for which full data is provided.

 

Symbols denoting electrodes/elements and electrode/element connections
f  Heater
k  Cathode
g Grid: Grids are distinguished by means of an additional numeral:
the electrode nearest to the cathode having the lowest number.
a Anode
m External conductive coating
m’ Rimband
Q Fluorescent screen
ic. Tube pin which must not be connected externally
nc Tube pin which may be connected externally
 

Symbols denoting voltages
Unless otherwise stated, the reference point for electrode voltages is the cathode.
Vv Symbol for voltage, followed by a subscript denoting the relevant electrode/element
Ve Heater voltage
Vp-p Peak-to-peak value of a voltage
Vp Peak value of a voltage
VGR Grid 1 voltage for visual extinction of focused raster (grid drive service)
VKR Cathode voltage for visual extinction of focused raster (cathode drive service)

Symbols denoting currents
| Symbol for current followed by a subscript denoting the relevant electrode
Fo Heater current (RMS value)
Note: The symbols quoted represent the average value of the current, unless otherwise stated.

Symbols denoting capacitances

See IEC publication 100

Symbols denoting resistances and impedances
R Symbol for resistance followed by a subscript for the relevant electrode pair. When only one subscript is given the second electrode is the cathode.
Zz Symbol for impedance followed by a subscript for the relevant electrode pair. When only one
subscript is given the second electrode is the cathode.

Symbols denoting various quantities
L Luminance
f Frequency
H Magnetic field strength.

  

GENERAL OPERATIONAL RECOMMENDATIONS

INTRODUCTION
Equipment design should be based on the characteristics as stated in the data sheets. Where deviations from these general recommendations are permissible or necessary, statements to that effect will be made. If applications are considered which are not referred to in the data sheets of the relevant tube type, extra care should be taken with circuit design to prevent the tube being overloaded due to unfavourable operating conditions.

SPREAD IN TUBE CHARACTERISTICS
The spread in tube characteristics is the difference between maximum and minimum values. Values not qualified as maximum or minimum are nominal ones. It is evident that average or nominal values, as well as spread figures, may differ according to the number of tubes of a certain type that are being checked. No guarantee is given for values of characteristics in settings substantially differing from those specified in the data sheets.

SPREAD AND VARIATION IN OPERATING CONDITIONS
The operating conditions of a tube are subject to spread and/or variation. Spread in an operating condition is a permanent deviation from an average condition due to, e.g.. component value deviations. The average condition is found from such a number individual cases taken at random that an increase of the number will have a negligible influence. Variation in an operating condition is non-permanent (occurs as a function of time). e.g .. due to supply voltage fluctuations. The average value is calculated over a period such that a prolongation of that period will have negligible influence.

LIMITING VALUES
Limiting values are in accordance with the applicable rating system as defined by IEC publication 134. Reference may be made to one of the following 3 rating systems. Absolute maximum rating system. Absolute maximum ratings are limiting values of operating and environmental conditions applicable to any electronic device of a specified type as defined by its published data, and should not be exceeded under the worst probable conditions. These values are chosen by the device manufacturer to provide acceptable serviceability of the device, taking no responsibility for equipment variations, environmental variations, and the effects of changes in operating conditions due to variations in the characteristics of the device under consideration and of all other electronic devices in the equipment. The equipment manufacturer should design so that, initially and throughout life, no absolute maximum value for the intended service is exceeded with any device under the worst probable operating condit- ions with respect to
supply voltage variation, equipment components spread and variation, equipment control adjustment, load variations, signal variation, environmental .conditions, and spread or variations in characteristics of the device under considerations and of all other electronic devices in the equipment.

Design-maximum rating system.
Design-maximum ratings are limiting values of operating and environ- mental conditions applicable to a bogey electronic device* of a specified type as defined by its pub- lished data, and should not be exceeded under the worst probable conditions. These values are chosen by the device manufacturer to provide acceptable serviceability of the device, taking responsibility for the effects of changes in operating conditions due to variations in the charac- teristics of the electronic device under consideration. The equipment manufacturer should design so that, initially and thoughout life, no design-maximum value for the intended service is exceeqed with a bogey device under the worst probable operating conditions with respect to supply-voltage variation, equipment component variation, variation in char- acteristics of all other devices in the equipment, equipment control adjustment, load variation, signal variation and environmental conditions.

Design-centre rating system.
Design-centre ratings are limiting values of operating and environmental conditions applicable to a bogey electronic device* of a specified type as defined by its published data, and should not be exceeded under average conditions. These values are chosen by the device manufacturer to provide acceptable serviceability of the device in average applications, taking responsibility for normal changes in operating conditions due to rated supply-voltage variation, equipment component spread and variation, equipment control adjustment, load variation, signal variation, environmental conditions, and variations or spread in the characteristics of all electronic devices. The equipment manufacturer should design so that, initially, no design-centre value for the intended service is exceeded with a bogey electronic device* in equipment operating at the stated normal supply voltage.

If the tube data specify limiting values according to more than one rating system the circuit has to be
designed so that none of these limiting values is exceeded under the relevant conditions.
In addition to the limiting values given in the individual data sheets the directives in the following
paragraphs should be observed.

HEATER SUPPLY
For maximum cathode life and optimum performance it is recommended that the heater supply be designed at the nominal heater voltage at zero beam current. Any deviation from this heater voltage has a detrimental effect on tube performance and life, and should therefore be kept to a minimum. Jn any case the deviations of the heater voltage must not exceed+ 5% and -10% from the nominal value at zero beam current. Such deviations may be caused by:

• mains voltage fluctuations;
• spread in the characteristics of components such as transformers, resistors, capacitors, etc.;
• spread in circuit adjustments;
• operational variations.

• A bogey tube is a tube whose characteristics have the published nominal values for the type. A bogey tube for any particular application can be obtained by considering only those characteristics which are directly related to the application.

CATHODE TO HEATER VOLTAGE
The voltage between cathode and heater should be as low as possible and never exceed the limiting values given in the data sheets of the individual tubes. The limiting values relate to that side of the heater where the voltage between cathode and heater is greatest. The voltage between cathode and heater may be d.c., a.c., or a combination of both. Unless otherwise stated, the maximum values quoted indicate the maximum permissible d.c. voltage. If a combination of d.c. and a.c. voltages is applied, the peak value may be twice the rated Vkf; however, unless otherwise stated, this peak value shall never exceed 315 V. Unless otherwise stated, the Vkf max. holds for both polarities of the voltage; however, a positive cathode is usually the most favourable in view of insulation during life. A d.c. connection should always be present betweeh heater and cathode. Unless otherwise specified the maximum resistance should not exceed 1 M.Q; the maximum impedance at mains frequency shou Id be less than 100 k.OHM.

INTERMEDIATE ELECTRODES (between cathode and anode)
In no circumstances should the tube be operated without a d.c. connection between each electrode and the cathode. The total effective impedance between each electrode and the cathode shou Id never exceed the published maximum value. However, no electrode should be connected directly to a high energy source. When such a connection is required, it should be made via a series resistor of not less
than 1 k.OHM.

CUT-OFF VOLTAGE
Curves showing the limits of the cut-off voltage as a function of grid 2 voltage are generally included in the data. The brightness control should be so dimensioned that it can handle any tube within the limits shown, at the appropriate grid 2 voltage. The published limits are determined at an ambient illumination level of 10 lux. Because the brightness of a spot is in general greater than that of a raster of the same current, the cut-off voltage determined with the aid of a focused spot will be more negative by about 5 Vas compared with that of a focused
raster.

LUMINESCENT SCREEN
To prevent permanent screen damage, care should be taken: - not to operate the tube with a stationary picture at high beam currents for extended periods; - not to operate the tube with a stationary or slowly moving spot except at extremely low beam currents; - if no e.h.t. bleeder is used, to choose the time constants of the cathode, grid 1, grid 2, and deflection circuits, such that sufficient beam current is maintained to discharge the e.h.t. capacitance before deflection has ceased after equipment has been switched off.

EXTERNAL CONDUCTIVE COATING
The external conductive coating must be connected to the chassis. The capacitance of this coating to the final accelerating electrode may be used to provide smoothing for the e.h.t. supply. The coating is not a perfect conductor and in order to reduce electromagnetic radiation caused by the line time base and the picture content it may be necessary to make multiple connections to the coating.
See also 'Flashover'.

METAL RIMBAND
An appreciable capacitance exists between the metal rimband and the internal conductive coating of the tube; its value is quoted in the individual data sheets.To avoid electric shock, a d.c. connection should be provided between the metal band and the external conductive coating. In receivers where the chassis ,can be connected directly to the mains there is a risk of electric shock if access is made to the metal band. To reduce the shock to the safe limit, it is suggested that a 2 Mil resistor capable of handling the peak voltages be inserted between the metal band and the point of contact with the external con- ductive coating. This safety arrangement will provide the necessary insulation from the mains but in the event of flashover high voltages will be induced on the metal band. It is therefore recommended that the 2 Mil resistor be bypassed by a 4, 7 n F capacitor capable of withstanding the peak voltage determined by the voltage divider formed by this capacitor and the capacitance of the metal rimband
to the internal conductive coating, and the anode voltage. The 4, 7 n F capacitor also serves to improve e.h.t. smoothing by addingthe rimband capacitance to the capacitance of the outer conductive coating.

FLASHOVER
High electric field strengths are present between the gun electrodes of picture tubes. Voltages between gun electrodes may reach values of 20 kV over approx. 1 mm. Although the utmost precautions are taken in the design and manufacture of the tubes, there is always a chance that flashover will occur. The resulting transient currents and voltages may be of sufficient magnitude to cause damage to the tube itself and to various components on the chassis. Arcing terminates when the e.h.t. capacitor is discharged. Therefore it is of vital importance to provide protective circuits with spark gaps and series resistors, which should be connected according to Fig. 1. No other connections between the outer conductive coating and the chassis are permissible. As our picture tubes are manufactured in Soft-Flash technology, the peak discharge currents are limited to approx. 60 A, offering higher set reliability, optimum circuit protection and component savings (see also Technical Note 039). However this limited value of
60 A is still too high for the circuitry which is directly connected to the tube socket. Therefore Soft-Flash picture tubes should also be provided with spark gaps.

IMPLOSION PROTECTION
All picture tubes employ integral implosion protection and must be replaced with a tube of the same type number or recommended replacement to assure continued safety.

HANDLING
Although all picture tubes are provided with integral implosion protection, which meets the intrinsic protection requirements stipulated in the relevant part of IEC 65, care should be taken not to scratch or knock any part of the tube. The tube assembly should never be handled by the neck, deflection unit or other neck components. A picture tube assembly can be lifted from the edge-down position by using the two upper mounting lugs. An alternative lifting method is firmly to press the hands against the vertical sides of the rimband. When placing a tube assembly face downwards ensure that the screen rests on a soft pad of suitable material, kept free from abrasive substances. When lifting from the face-down position the hand should be placed under the areas of the faceplate close to the mounting lugs at diagonally opposite corners of the faceplate.

When lifting from the face-up position the hands should be placed under the areas of the cone close
to the mounting lugs at diagonally opposite corners of the cone.

In all handling procedures prior to insertion in the receiver cabinet there is a risk of personal injury as a result of severe accidental damage to the tube. It is therefore recommended that protective clothing shou Id be worn, particularly eye shielding. When suspending the tube assembly from the mounting lugs ensure that a minimum of 2 are used; UNDER NO Cl RCUMSTANCES HANG THE TUBE ASSEMBLY FROM ONE LUG. If provided the slots in the rimband of colour picture tubes are used in the mounting of the degaussing coils. it is not recommended to suspend the tube assembly from one or more of these slots as permanent deformation to the rimband can occur. Remember when replacing or servicing the tube assembly that a residual electrical charge may be carried by the anode contact and also the external coating if not earthed. Before removing the tube assembly from the equipment, earth the external coating and short the anode contact to the coating.

PACKING
The packing provides protection against tube damage under normal conditions of shipment or handling. Observe any instructions given on the packing and handle accordingly. The tube should under no circumstances be subjected to accelerations greater than 350 m/s2.

MOUNTING
Unless otherwise specified on the data sheets for individual tubes there are no restrictions on the position of mounting. The tube socket should not be rigidly mounted but should have flexible leads and be allowed to move freely. It is very desirable that tubes should not be exposed to strong electrostatic and magnetic fields.

DIMENSIONS
In designing the equipment the tolerances given on the dimensional drawings should be considered. Under no circumstances should the equipment be designed around dimensions taken from individual tubes.