Philips L01H.1A Service Manual Download

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Circuit Description

The ‘Ewdrive’ signal from pin 15 of IC7200 takes care for the
correct correction. It drives FET TS7400. It also corrects
breathing of the picture, due to beam current variations (the
EHT varies dependent of the beam current). This correction is
derived from the ‘EHTinformation’ line.
Two protections are built-in for the E/W circuit: over-current and
over-voltage protection. See paragraph Power Supply.

Panorama (if present)
The panorama function is only used in 16:9 sets. This is a
function to enable the 4:3 and Super-Wide feature. It drives the
‘Bass_panorama’ line, to activate relay 1400. When this relay
is switched on, the capacitors 2453//2454 are added in parallel
to the default S-correction capacitors 2456//2457. This results
in an increased capacitance, a lower resonance frequency of
the line deflection coil and the S-correction capacitors and
therefore a less steep S-corrected line deflection current.

9.5.4

Rotation (if present)

To cope with the different earth magnetism situations in the
world, a rotation coil is added. This coil is controlled by the
rotation circuitry (see diagram A15).
The amount of frame rotation is user controlled via the the
PWM output (pin 77) of the UOC.
With the tilt setting at ‘-10’, the PWM duty cycle is 0.1 (leftmost
tuning).
With the setting at ‘+10’, the duty cycle is 0.9 (rightmost tuning).
The output of amplifier IC7171 is a DC-voltage in the range
from 0 (user setting = -10), via 6 V (user setting = 0) to 12 V
(user setting = +10).

9.6

Power Supply

Figure 9-6

Figure 9-7

9.6.1

Introduction

The supply is a Switching Mode Power Supply (SMPS). The
frequency of operation varies with the circuit load. This ‘Quasi-
Resonant Flyback’ behaviour has some important benefits
compared to a ‘hard switching’ fixed frequency Flyback
converter. The efficiency can be improved up to 90%, which
results in lower power consumption. Moreover the supply runs
cooler and safety is enhanced.
The power supply starts operating when a DC voltage goes
from the rectifier bridge via T5520, R3532 to pin 8. The
operating voltage for the driver circuit is also taken from the
‘hot’ side of this transformer.
The switching regulator IC7520 starts switching the FET ‘on’
and ‘off’, to control the current flow through the primary winding
of transformer 5520. The energy stored in the primary winding
during the ‘on’ time is delivered to the secondary windings
during the ‘off’ time.
The ‘MainSupply’ line is the reference voltage for the power
supply. It is sampled by resistors 3543 and 3544 and fed to the
input of the regulator 7540/6540. This regulator drives the
feedback optocoupler 7515 to set the feedback control voltage
on pin 3 of 7520.
The power supply in the set is ‘on’ any time AC power goes to
the set.

Derived Voltages
The voltages supplied by the secondary windings of T5520 are:
•

‘MainAux’ for the audio circuit (voltage depends on set
execution, see table below),

•

3.3 V and 3.9 V for the microprocessor and

•

‘MainSupply’ for the horizontal output (voltage depends on
set execution, see table below).

Other supply voltages are provided by the LOT. It su50
V (only for large screen sets), +13 V, +8 V, +5 V and a +200 V
source for the video drive. The secondary voltages of the LOT
are monitored by the ‘EHTinformation’ lines. These lines are
fed to the video processor part of the UOC IC7200 on pins 11
and 34.
This circuit will shut ‘off’ the horizontal drive in case of over-
voltage or excessive beam current.

Demag

Ctrl

Gnd

Vcc

Drain

HVS

Driver

Sense

LINE

TEA1507

SENSE

OUT