Philips es1e Service Manual page 92

EN 92 9.
extra current generates a parabolic waveform across 2419 at
the centre scanning position. The parabolic waveform is
superimposed (series-added) onto the S-cap voltage (2417/
2418); in this way, a more parabolic waveform is obtained
which corrects the inner pincushion distortion.
East West correction Circuit:
Together with diode modulator 2413/2416/6404, components
6471/7406/3425/2425 form the main East-West correction
circuit. The circuit is a current drive circuit driven by MOSFET
7406. 3425 and 2425 function as a simple RC filter with the task
of filtering the horizontal pulses in the diode modulator stage.
The parabolic current source for the EW-drive comes from the
SSB and modulates the diode modulator voltage by means of
7406. Because 7406 is in series with Scap 2417/2418), the
diode modulator voltage plus the Scap voltage are always
equal to Vbatt. So, by modulating the diode modulator voltage,
we are able to modulate the Scap voltage, and so the deflection
current and scanning width as well.
EHT-info Compensation:
In addition to the EHT-info compensation feedback to the SSB
IC, components 3422/3423/6424/3424/3435/6425/3437/2437/
2422 are the EHT-info compensation circuit that injects beam
information into the East-West correction circuit to achieve
better compensation.
Waveform "EHT-info" is a voltage source which is derived from
Ibeam; the voltage is injected via the EHT-info compensation
circuit mentioned above, and modulates the East West circuit.
Beam Current and Horizontal Flyback:
The beam current is determined by 3480/3491/3453/3492/
6478 (see circuit diagram A2), while 2450/2451 filters out the
high frequency info.
The horizontal flyback circuit is provided with an X-ray
protection function; for this reason the combined circuit bears
the name Hfb_Xray_Prot. Hfb is derived from the heater pulses
via 2477 and 2476 and clamped by 3477/6474. The protection
is realized by 7486. The SSB monitors the Hfb_Xray_Prot
voltage and will go into protection mode if this voltage is low
without pulses.
9.2.4 Vertical Deflection
IC 7455 (see circuit diagram A2) is the differential vertical
deflection amplifier. The amplification gain is determined only
by 3461/3476 and 3470/3471/3472. The SSB IC output is a
differential vertical current source to 7455 and its signal is
amplified and output as a vertical deflection current through the
vertical yoke coil.
IC 7455 has a separate flyback supply (on its VFB pin) which is
tapped from the positive portion of the heater voltage. The
flyback heater voltage charges 2461 via 6476/3487 and is
clamped by 6458.
The vertical scanning voltage (on pin V-OUT of 7455) varies
between +13V and -14V.
Components 3466/2468 are for pole-zero compensation
purposes and suppress oscillation tendencies.
Components 3467/3468 suppress horizontal coupling, and
also suppress noise.
Components 3459/6459 are part of the circuit which protects
the CRT tube from burning in, in case someone accidentally
unplugs the vertical yoke or disconnects the power supply of
7455. Without this protection, the picture tube neck may be
Circuit Descriptions, Abbreviation List, and IC Data Sheets
ES1E
damaged if the vertical scanning circuit is not working and all
the beam energy is concentrated on one spot of the CRT neck.
The function of diode 6457 is to isolate the small signal supply
from the flyback supply boost up voltages.
9.2.5 Protection
The protections are realized by 7407/7456/7486. All the
protection voltages coming from the various protection circuits
like: the vertical protection (3459/6459), the bridge coil
protection (5411/6405/3479), the X-ray protection (6480/7408/
3460/3462/3465/3469) and the East West protection (7403/
3473/3488/3417/2495) are combined in 7407/7456/7586.
If a protection circuit is triggered, the protection triggering
voltage will turn on 7407 and consequently 7486, which will pull
the Hfb-Xray_Prot voltage low. The SSB will respond to this
triggering signal and will shut down the deflection circuit
9.3 Software Upgrading
In this chassis, you can upgrade the software via ComPair.
This offers the possibility, to replace the entire SW image
without having to remove the flash-RAM from its socket. You
can find more information on how this procedure works in the
ComPair file. It is possible that not all sets are equipped with
the hardware, needed to make software upgrading possible. To
speed up the programming process, the firmware of the
ComPair interface can be upgraded. See Chapter "Service
Modes ..."; paragraph "ComPair" - "How To Order" for the order
number.