REX Mod. L12 CHASSIS BS201.0 CRT TUBE PHILIPS A31-120W.

CRT TUBE PHILIPS A31-120W.

 TELEVISION TUBE PHILIPS - MULLARD A31-120W

QUICK REFERENCE DATA

31cm (12in) rectangular direct viewing television tube with metal backed screen
and reinforced envelope. A separate safety screen is not required. Especially
for use in portable receivers with push—through presentation.

Deflection angle 110 deg
Focusing Electrostatic

Light transmission 50 %
Maximum overall length 233 mm

This data should be read in conjunction with
GENERAL OPERATIONAL RECOMMENDATIONS - TELEVISION PICTURE TUBES

HEATER
Vh 11 V
Ih 75 mA

The maximum total deviation from the nominal heater voltage is 15%.

The deviation consists of 7% maximum continuous deviation, for example, due to
component spread and 10% maximum temporary deviation.

For supply direct from a battery, the heater voltage cycle must be within the limits
of the graph on page 10 .

OPERATING CONDITIONS

Va2 ’ 34 11 kV
VA3 (focus electrode) control range 0 to 350 V
Va1 250 V
Vg for visual extinction of focused raster -35 to -69 V
*Vk for visual extinction of focused raster 32 to 58 V

*For cathode modulation, all voltages are measured with respect to grid.

SCREEN
Metal backed
Fluorescent colour White
Light transmission (approx.) 50 %

FOCUSING Electrostatic

DEFLECTION Magnetic

Diagonal deflection angle 110 deg
Horizontal deflection angle 99 deg
Vertical deflection angle 80 deg

The deflection coils should be designed so that their internal contour is in accordance
with the reference line gauge shown on page 4 .

CAPACITANCES
cg_aLL 7 0 pF
ck_all 3 0 pF
ca2’a4_M 450 to 900 pF
ca2’a4_B 300 pF

EXTERNAL CONDUCTIVE COATING

This tube has an external conductive coating, M, which must be connected to chassis,
and the capacitance of this coating to the final anode is used to provide smoothing
for the e.h.t. supply. The electrical connection to this coating must be made within
the area specified on the tube outline drawing.

RASTER CENTRING

See notes under this heading in ‘General Operational Recommendations — Television
Picture Tubes‘.

Centring magnet field intensity 0 to 800 A/ m
Maximum distance of centre of
centring field from reference line 4'? mm

Adjustment of the centring magnet should not be such that a general reduction in
brightness of the raster occurs.

REFERENCE LINE GAUGE see page 4
MOUNTING POSITION Any

The tube socket should not be rigidly mounted but should have flexible leads and be
allowed to move freely.

This tube is fitted with a pin protector in order to avoid damage to the glass base
due to bending of the base pins whilst handling the tube.

It is advisable to keep this pin protector on the base until it can be replaced by the
socket after the installation of the tube in any equipment .

TELEVISION TUBE A31-120W

RATINGS (DESIGN CENTRE SYSTEM unless otherwise stated)


Va2’a4 max. (at Ia2’a4=0) (see note 1) 12 kV
Va2’a4 min. (absolute limit) 8.5 kV
+V max. 500 V
3.3
-V max. 50 V
a3
V max 350 V
a1
V min. 200 V
3.1
-vgxpk) max. (see note 2) 350 V
-Vg max. (see note 3) 100 V
+-Ia3 max. 25 uA
+-Ia1 max. 5.0 pm
vh-k (cathode positive)
d.c. max. 110 V
pk max. 130 V
Rh_k max. 1 .0 M52
Zk_e max. (f =50Hz) 100 kOHM
R max. 1.5 MOHM
g-k
Zg_k max. (f =50Hz) 500 kOHM
RM_B min. 2 .0 MOHM

Notes
1. Adequate precautions should be taken to ensure that the receiver is protected
from damage which may be caused by a possible high voltage flashover within
the tube .

Maximum pulse duration 22% of one cycle with a maximum of 1.5ms.

The d.c . value of bias must not be such as to allow the grid to become positive
with respect to the cathode, except during the period immediately after switching
the receiver on or off when it may be allowed to rise to +2. 0V. It is advisable to
limit the positive excursion of the video signal to +5V(pk) max. This may be
achieved automatically by the series connection of a 10kQ resistor.

The metal band must be earthed by means of the tag provided.

The mounting lugs will not necessarily be in electrical contact with the metal
band.

WEIGHT
Tube alone (approx .) 2 . 8 kg