Philips DPTV465 Service Manual page 86

EN 86 9. DPTV465
sets the reference voltage for comparator "B", which is
compared with the voltage on the source of 7301. This voltage
is developed when 7301 turns "on", causing current to flow
through resistors 3308 and 3309. If 7301 fails, Resistors 3308
and 3309 should be replaced. These are one percent tolerance
resistors.
The Main Power supply produces: +130 V, +35 V, +22 V, -22
V, -35 Volt, a plus audio supply, and a minus audio supply. The
Audio supply is a plus and minus 23 Volts. This supplies the
digital audio amplifier located on the SSM (Small Signal
Module).
When troubleshooting, notice that the Hot Ground for the Main
Power supply is separated from the main Hot Ground on the
AC Input Panel by Choke 5330. To ensure correct readings,
use the Hot Ground in the Main power supply. If the power
supply is overloaded or the operating voltage is missing, the
voltage on pin 1 of the IC should be changing between 9.4 and
14.5 Volts. Each time the voltage reaches 14.5 Volts, drive
should appear on pin 3 of the IC. If a voltage is present on pin
1 that is greater than 14.5 Volts and there is no drive on pin 3,
the IC should be replaced. If drive is present on pin 3, check for
drive on the Drain of 7301. If drive is present here, check for a
short on the 130 Volt lines, a problem in the feedback circuit, or
a problem with the operating voltage.
9.3
Video
The HDR2004 is a multi-system PTV. It will accept:
•
RF inputs from NTSC, PAL, or SECAM.
•
Composite or SVHS inputs from NTSC, PAL, or SECAM
sources.
•
Component YPbPr inputs from 1fH NTSC, PAL, or
SECAM.
•
YPbPr or RGB inputs from 480p, 576p, or 1080i sources.
Composite Video or SVHS YC from the Side Jack panel is fed
to the video switch, located on the SSM (Small Signal Module).
The SSM video switch selects between the composite inputs or
SVHS inputs of the Side Jack panel or the inputs, located on
the SSM. AV1 and AV2 inputs are located on the SSM. AV3 is
Circuit Descriptions, List of Abbreviations, and IC Data Sheets
Figure 9-7 Video signal block diagram
Power Fail Shutdown
Figure 9-6 Power fail shutdown circuit
The +22 Volt supply is rectified by 6306 and the -22 Volt supply
is rectified by 6307. The voltage on pin 18 of 5300 is monitored
to detect a failure of the AC supply to the set. This circuit
signals the microprocessor in the event that AC is removed
from the set while it is turned "on". The voltage from pin 18 is
rectified by 6318 and is applied to the Shunt Regulator 7305.
Shunt Regulator 7305 is turned "on", keeping the Power Fail
and Protect lines Low. When AC is removed while the set is
"on", 7305 will turn "off" fast. This is because the filter capacitor
for the input to 7305 is small. When 7305 turns "off", the Power
Fail line goes "high" from the voltage on the +22 Volt line. The
microprocessor will shut the set down while it still has voltage
to operate.
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the Side Jack panel input. Selected composite video or YC is
fed to the SSB (Small Signal Board), which plugs into the SSM.
PAL, SECAM, or NTSC component video YPbPr is buffered
and fed to the SSB. Selected composite video is fed to the PIP
panel for the PIP window picture information. IF from the tuner
located on the SSM is fed to the SSB. Composite video from
the SSB, which is developed from the main Tuner, is fed to the
Video Output jack on the SSM. Switching "on" the PIP panel
selects between video from the Tuner on the PIP panel or
selected Video from the SSM. YUV for the main picture from
the SSB is fed to the PIP panel for the Picture in Picture
information to be inserted. After insertion of the PIP
information, the YUV signal is fed back to the SSB. A line
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