REX (ZANUSSI) MOD. M200B CHASSIS BS157-3B CRT TUBE ZANUSSI (PHILIPS) A50-120W.

The CRT IS A PHILIPS REBRANDED ZANUSSI WITH HIS LOGO AT THE TIME.


TELEVISION TUBE A50- 120W/R

QUICK REFERENCE DATA

50cm (20in) direct viewing television tube With metal backed screen
and reinforced envelope. A separate safety screen is not required.
Suitable for use in receivers with push-through presentation. This
tube is fitted with a ring trap base:

Deflection angle 110 deg
Focusing Electrostatic
Light transmission (approx.) ’ ’ 45 %
Maximum overall length 319 mm

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

HEATER
Suitable for series or parallel operation
Vh 6 . 3 V
Ib 300 mA

The limits of heater voltage and current are contained in ‘General
Operational Recommendations — Television Picture Tubes’.

Note - applies to series operation only

The surge heatervoltage must not exceed 9.5V r.m.s. when the supply is
switched on. A current limiting device maybe necessary in the circuit, to
ensure that this voltage is not exceeded.

OPERATING CONDITIONS
V 32’ £4 20 20 IN
V a3 (focus electrode control range) 0 to 400 0 to 400 V
V 400 500 V

a1Vg for visual extinction of focused raster -40 to -77 ~50 to -93 V

Vk for visual extinction of focused raster 36 to 66 45 to 80 V

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

SCREEN (Metal backed)
Fluorescent colour White
Light transmission (EPPFOX-) 45 96

FOCUSING Electrostatic

The range of focus voltage shown in ‘Operating Conditions’ results in opti-
mum overall focus at a beam current of 250UA. In general, acceptable
resolution will be obtained with a fixed focus voltage.

DEFLECTION (Magnetic)

Diagonal deflection angle E 110 deg
Horizontal deflection angle 98 deg
Vertical deflection angle ' ' 81 ~ deg

The deflection coils should be designed to provide a pull—back of 4 .0mm
on a. nominal tube . '

CAPACITANCES
cg_au 7.0 pl?‘
ck_an 5.0 pF
ca2’.a4_M 850 to 1300; pF <- br="">"a2,a4-B 50° PF

EXTERNAL CONDUCTIVE COATING

This tube has an external conductive coating, M, and in accordance with
the General Operational Recommendations this should be connected directly
to pin 5 and not to chassis. The electrical connection to this coating must
be made within the area specifiedon the tube outline drawing.

 The capacitance of this coating to the final anode is used to provide smoothing for the
e.h.t. supply.



For flashover protection of the receiver, parallel spark gaps are included
for all the electrodes in the base of this tube, and the common connection
is made to pin 5. These spark gaps are intended as part of a system for
full flashover protection. A direct connection must always be made from
pin 5 to chassis, and the external conductive coating returned to chassis
only via pin 5, using short leads. Any electrode supplied directly from a
high energy source (such as the h.t. line) should be provided with a series
resistor.

RASTER CENTRING

See note 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 57 mm

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




TELEVISION TUBE MOUNTING POSITION

Any. The tube socket should not be rigidly motmted but should have
flexible leads and be allowed to move freely. The bottom circumference of the
base shell will fall within a circle of 40mm diameter which is centred on

the perpendicular from the centre of the face.

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 imtil it can be replaced

by the socket after installation of the tube in any equipment.