SONY KV27FV15, KV32FV15, KV32FS10, KV32XBR250, KV36XBR250, KV32FV15, KV36FV15, KV36FS10
Parental Control Menu
Sony
V Chip equipped televisions contain the Parental Control Menu, which is located
in the Setup section. When it is selected, the user will be asked for a 4-digit
password. After this password is entered, the user will be asked to confirm it.
After confirmation, the password is set. Anytime the user wants to modify the
Parental Control Menu, the password must be entered.
Note: If the customer
forgets their password, the master Password 4357 can be
entered. This allows the customer to reset their password. No settings can be
changed until a new password is entered.
When
you have entered the password, an options menu will be displayed.
The options are as follows.
Parental
Lock: This is used to enable or disable the ratings system. This is
done by selecting On or Off.
Rating: There are four
ratings that can be selected.
ƒ Child – The child
selection is used to enable only TV-Y, TV-Y7, TV-G and G ratings.
ƒ Youth – The youth
selection is used to enable TV-PG and PG ratings. Ratings considered lower than these will also
be enabled.
ƒ Youth Adult –Tthe youth
adult selection enables TV-14 and PG-13 ratings in addition to lower ratings.
ƒ Custom – The custom
selection allows you to tailor the age and content ratings to your liking. The
picture below shows the menu that will be seen when custom is selected.
Here the user can select
ratings by age or content. If they do not want violence of any kind to be seen
but are not offended by strong language, they can select the V for PG-14. This
will block all V settings above PG-14
Power Supply Block
The power supply in the
AA2W chassis is located on the G board. AC from the outlet is applied to a
series of line filters and protection devices and eventually applied to the
standby supply, AC rectifier and degauss circuits. The Standby supply is a
switching supply whose output is applied to a 5-volt regulator. The output from
the regulator exits the G board at CN641/10. It is applied to various
components in the set that need to be powered when the set is OFF. These
include the Micon and the remote sensor When the set is turned ON by using
either the power button or the remote control, 5 volts is applied to CN641/11.
This 5 volts is used to turn RY600 Power Relay ON. When the relay closes, a
click is heard. Closing the relay allows the rectified ac voltage to be applied
to the cnverter circuit.
The converter begins operation when this voltage is applied. The power ON line
is also applied to the soft start circuit. The soft start circuit holds the B+
voltage low while the power supply filters charge by controlling the voltage
present across the control winding. The control winding determines the
switching frequency of the converter. After soft start operation is complete,
the regulation circuit takes over operation of the control winding. This allows
the converter’s output to be coupled through T605 to the secondary supplies.
These supplies supply power to the rest of the set.
The regulation circuit monitors the +135 volt line. Shortly after the click of the power relay at
turn ON, another click is heard.
This click is RY601 Degauss Relay closing. This may be accompanied by a hum
sound that indicates the operation of the degaussing coils. After the AKB
circuit operation is considered normal, the degaussing relay opens.
This is the third click that occurs about 8-10 seconds after the unit is turned
ON.
During operation of the set, the +135 volt line is monitored for DC protection.
This protection circuit is used in conjunction with the latch to switch the
Power ON line LOW if a failure should occur. This will turn RY600 Power Relay
OFF and turn the power supply OFF. In addition to this protection circuit a
foldback circuit can also shut down the power supply.
The fold back circuit compares the secondary’s +12 volt output to a voltage on
the primary side. If there is a problem with either one of these circuits, the
set will shut down.
Standby Power Supply
The standby power supply
is a switching power supply used to create Standby 5V. The Standby 5V line is
used to power the Tuning Micon and EEPROM and any other circuits which need
power when the set is OFF.
Converter
Operation
Operation
of the Standby power supply begins when the set is plugged in.
The AC line voltage is applied across the standby power supply. The AC low side
is ground for this circuit. The AC high side is applied to a half wave
rectifier consisting of D621 and D622. Two diodes are used so that there will
be protection should one of them fail. This voltage is then applied to T621/1
SRT Input through R639. R639 is a fusible resistor used for current limiting
and failure protection. It will open if the standby switching circuit draws
excessive current. Please note that the board has T621 SBT silk-screened on it.
This differs from the service manual, which calls T621 SRT.
When the voltage is applied to T621/1 SRT Input, current flows through the
winding and R631 to Q621/G. Q621 Converter is a FET with added protection. When
a positive voltage is applied to the gate, it begins to conduct drain to
source. This reduces the voltage at T621/3 to close to zero. Normally this
would reduce the voltage at Q621/G, but a voltage is supplied to the gate
through R632 and C630 from T621/4. This voltage is induced into the secondary
winding of T621/4 when current flows through the winding between T621/1 and
T621/3. The voltage is not permanent due to C630. As C630 charges, it reduces
the voltage at Q621/G. Once this voltage falls below a certain threshold, Q621
Converter turns OFF.
Once Q621 Converter turns OFF, all polarities are reversed. This reversal of
polarity helps speed up turn OFF of Q621. D623, along with C631 and R640, form
a snubber network (voltage clamp). This network clamps excessive voltage
overshoot caused by the collapsing magnetic field of T621 SRT and returns the
excessive voltage to C629. When the field collapses fully, current begins to
flow through T621/1 and 3.
Regulation
Changing
the frequency of the switching regulates the output voltage at the secondary
winding comprised of T621/8 and 9. Taking a sample voltage from T621/4 and
applying it to rectifiers D624 and D625 does this. As this voltage rises and
falls, the rectified voltage is applied to Q622/B through R634. When Q622
begins to conduct, it lowers the voltage at Q621/G and changes the switching
frequency.
The changing frequency will change the amount of voltage coupled to the secondary
winding consisting of T621/8 and 9. If the load on the secondary output
increases, the frequency of switching will decrease. This brings the frequency
of the converter closer to the optimum operating frequency of T621 SRT. Moving
closer to this optimum frequency causes more voltage to be provided at T621/9.
The opposite occurs when the load on the supply decreases. This causes the
frequency of operation to be increased and the amount of voltage coupled to
T621/9 to be decreased.
The supply typically operates at 45 kHz when the set is OFF and at about 30 kHz
when the set is operating. The incoming line voltage also effects the frequency
of switching operation.
Over Current Protection
(OCP)
Monitoring
the voltage across R637 is used for over current protection.
This voltage is representative of the amount of current flowing through Q621
Converter since it is in series with the transistor. If this voltage should
rise to .6 volts, it will cause Q622 to turn ON. If Q622 were to turn ON, it
would shunt Q621/G voltage to ground. This would cause Q621 Converter to stop
conducting.
Over
Voltage Protection (OVP)
Over
voltage protection is done by rectifying the voltage at T621/6 with D627. This
voltage is filtered by C636 and applied to D626 through R638.
If this voltage should rise above 6.2 volts, D626 begins to conduct. When its
conduction allows Q622 Protect to turn ON, over voltage protection is employed.
Q622 Protect turns ON and grounds Q621/G, which stops the converter from
switching.
D699 is also used for OVP. The signal from T621/4 is rectified by D698.
This creates a negative voltage across C699. If this negative voltage becomes
great enough, D699 conducts and the Q621/G voltage is brought lower.
Secondary Output
The
power coupled through T621 SRT places a voltage on T621/9 that, when rectified
and filtered by D628 and C637, is 7.2 volts. This voltage is constant due to
the regulation circuit on the primary side of T621 SRT.
This 7.2 volts is applied to Q646/E for backup during the start of regulation
by the regular power supply.
It is also applied to IC622 5-Volt Regulator, which regulates its output to 5 volts.
This 5 volts is sent to CN641/10 which connects to the A board and powers the
Tuning Micon and other circuits. It is also applied to RY600
Power Relay.
Checking
Q621
Testing
a MOSFET device is simple. The leads show infinite resistance to each other
except for drain to source in one direction because of the presence of a
protection diode.
To prove the device is functional:
1. Connect the negative lead of the ohmmeter to the SOURCE lead.
2. Touch the ohmmeter positive lead to the gate, to pre-charge it.
3. Connect the ohmmeter positive lead to the DRAIN. If the device is good
you will get a resistance reading of about 400-1k ohms.
Some DVMs do not produce enough DC voltage in the ohms mode. The diode check
mode can be used with these models. When using the diode mode, a low voltage
drop is shown after pre-charging the gate.
Power On-Degaussing
Power On
When
the set is plugged in, the AC voltage is applied through F601, T601 and T602.
Additional components C605, VDR601, C604 and VDR602 are across the AC line
input. They are in place for protection from AC line spikes and surges. This AC
voltage is applied to the standby power supply and will be applied to D602
Bridge Rectifier when RY600 Power Relay is closed. R623 and R664 will limit the
current when the relay is initially closed.
When the customer turns the set ON using either the remote or the power switch,
a 5-volt signal is output from IC001/62 Tuning Micon O-Relay.
This HIGH is sent to the G board via the wiring harness between CN1641 on A
board and CN641 on the G board.
This signal is used to turn Q648 ON. When Q648 turns ON, it places a LOW at its
collector. This causes RY600 to energize, closing the contact and allowing
current to flow to D602 Bridge Rectifier. The LOW from Q648/C is also applied
to the Q646 Backup and Q647 Soft Start transistors.
Voltage
Doubler
D602
Bridge Rectifier is used with C606, C607, D629 and D630 to form a voltage
doubler. Therefore, the output of the voltage doubler is approximately 310 VDC.
This voltage will be referred to as Converter B+. Converter B+ is applied to
the converter circuit through R607. R607 is a fusible resistor. If the
converter circuit draws too much current, it will open. When RY600 Power Relay
is closed, a click is heard. When the Converter B+ is applied to the converter
circuit, it will begin to operate and supply power to the rest of the set.
Degaussing
When
the set is turned ON, a click is heard from the Power Relay RY600.
About one second later another click is heard from RY601 Degauss Relay. After
this a loud hum can be heard. This indicates that the degaussing circuit is
operating. The degaussing circuit operates because every time the set is turned
ON, a HIGH is output from IC001/33 Tuning Micon O-HP SEL. This HIGH is applied
via the cable between CN1641 on the A board and CN641 on the G board. This
voltage is used to turn ON Q644.
When Q644 is turned ON, RY601 is energized, causing current to flow from the AC
line through THP601 and THP602. When current flows, 120VAC is applied to the
degaussing coils. When this occurs, a hum can be heard.
THP601 and THP602 are thermistors whose resistance increases as they get
warmer. The thermistors should read less than 10 ohms when cold. The current flowing through them when voltage
is applied to the degaussing coils is great and causes the thermistors to open
after a few seconds.
This stops the action of the degaussing coils since no more current is flowing
through them. The set will not degauss properly if the set is turned OFF and ON
again quickly. You typically need to wait at least a few minutes until the
thermistors have cooled to degauss again.
If the degaussing circuit is not operating, no hum will be heard when the set
is turned ON. It is also likely that purity problems will occur since the tube
could become magnetized. Room vibrations
may cause the contacts of RY601 to make contact when they are not supposed to,
causing the degauss coils to be activated while the set is producing a picture.
If this occurs, the customer may complain about an intermittent rainbow pattern
or intermittent loss of purity. If a customer complains about this, try
replacing RY601.
Converter
The function of the
converter is to switch the Converter B+ voltage through a transformer’s primary
winding. This switching will produce a signal that will be coupled to the
transformers secondary windings where they are rectified and used to supply
various voltages to the set. The frequency of this switching is controlled to
maintain a consistent value on the +135 volt line. Changing the frequency of
the switching can be used for regulation due to the efficiency characteristics
of the transformer. A second transformer with a cross-inductance winding is
used to create a “dual tank oscillator”. The voltage across the
cross-inductance winding or control winding is used to change the value of the
inductance in the tank circuit and consequently change the frequency of
switching.
Initial
Start Up
When
RY600 Power Relay (not shown) is closed, 300 VDC is developed and applied to
R607. Converter B+ is then applied to C613 and C615.
C613 ensures that the bottom transistor IC601-1 turns ON initially. When IC601-1
turns ON, there is a current path through C615, T605/1 and 2, T603/1 and 2,
through IC601-1/ C-E to ground. The voltage applied to IC601-1/B by T603/4
sustains this current path. This voltage at T603/4 is developed by the
expanding magnetic field being produced by the current flowing through T603/1
and 2. When the magnetic field in T603 PRT stops expanding, IC601-1 turns OFF.
When this occurs, a voltage is induced by the collapsing magnetic field at
T603/3 that turns IC601-2 ON.
This provides a discharge path for C615. When C609 is fully charged, IC601-2
will turn OFF. This cycle will continue to repeat itself. As the voltage across
T604/7 and 8 Control Winding changes, the inductance of the other windings will
change. This will determine the frequency of switching.
Soft Start
The
voltage across T604/7 and 8 Control Winding determines the frequency of
operation. The control winding is a cross inductance winding.
At initial startup the converter has to switch above the optimum frequency of T605
PIT. A soft start circuit is used to ensure that this occurs. The soft start
circuit will ensure that a voltage of approximately 7 volts will be applied
across T603/7 and 8 Control Winding. After the converter begins to run, the
voltage from the Vcc Rect. line is applied to T603/8 through D612. The voltage
applied to T603/7 will then come from the regulator circuit instead of soft
start.
Regulation
The
frequency of the power supply is dependent on the load that it sees. When the
picture brightness increases, the load increases, lowering the voltage across
T603/7 and 8. When this occurs, the frequency of the oscillator decreases,
allowing T605 to supply more current to the secondary windings. This keeps the
135V line from lowering in voltage.
The following table shows what occurs with different loads on the supply. Note
that the oscillator frequency changed, but the 135V line remained within a few
tenths of a volt of its value. You should also be aware that the frequency of
operation is also dependent on the input AC line voltage.
Troubleshooting
One
of the most common failures in switching power supplies are the converter
transistors or in the case of this power supply, IC601. IC601 actually contains
two identical transistors. They are assembled in this package so that their
gain and other characteristics are closely matched.
Generally when these transistors fail, they fail by shorting C-E in one or both
of the transistors. This causes the fusible resistor to open due to excessive
current draw. The fusible resistor in this case is R607. The symptom in this
set is that you hear only one relay click on initial power up instead of three.
Usually you would hear two, the power relay followed by the degaussing relay.
This would be followed by another click about ten seconds later that indicates
the degaussing relay is turned OFF. You can check the voltages around IC601 to
troubleshoot this problem. There would be no voltages present since R607 would
be open due to the shorted transistor.
You should always check the horizontal output for shorts when the converter
transistor has failed. It is also a good idea to unload the power supply and
bring the line voltage up slow using a variac.
When performing this procedure, set your variac to zero. Jump the relay contacts.
Warning: By jumping the
relay contacts you have defeated the protection circuitry of the power supply.
Plug the unit into the variac
and bring the AC voltage to 30 VAC. You should have stable oscillation at this
point. Check to see how much current is being drawn from the AC line. The
current drawn should be minimal since the supply is unloaded. Check the
voltages at the points in the table below. The oscillator voltage and frequency
are measured at T603/2. The secondary voltages can be easily checked at CN641
and CN642. Increase the line voltage by ten volts and check each item in the
table again. Repeat this
procedure at 50 and 60 VAC.
Warning: It is not
recommended that the power supply be operated unloaded above 60VAC.
Another
problem that may occur is that the switching never starts. To troubleshoot this
type of problem, remove one lead from C615. When you power the set ON, you should
have a DC voltage of half the Converter B+ at T603/2. This is where the
switching waveform would normally be present. If the voltage is lower at this
point, suspect an open related to IC601-2 or a leaky component related to
IC601-1. If the voltage is high at this point, suspect an open related to
IC601-1 or a leaky component related to IC601-2.
Soft
Start-Regulation-Foldback
The three circuits
discussed here all have an effect on the voltages across T603/7 and 8. This
winding of the PRT is a cross inductance winding or control winding that
controls the frequency at which the converter operates.
Soft
Start
At
power ON, C602, which is discharged, has a 0V potential at its + terminal. This
biases Q645 ON, via R647. With this transistor ON, it allows the standby
unregulated from Q646/E to be applied across T603/7 and 8.
This voltage is passed through Q646 Backup since the same line that turns RY600
Power Relay ON turns it ON. The greater the voltage across this winding, the
higher the converter frequency and the lower the efficiency of T605 PIT. This
is discussed in the Converter section. Therefore, the start up secondary
voltages will be reduced considerably. As C602 charges, the voltage difference
between T603/7 and 8 diminishes.
As this voltage lowers, the secondary voltages will rise. When the Vcc Rectifier
voltage is larger than the Standby unregulated voltage, D612 will begin to
conduct and the Vcc Rectifier voltage will control T603/8. Also at this time
C602 will be fully charged and IC643 Control IC will take control over T603/7.
The difference in voltage between T603/7 and 8 will regulate the converters
operating frequency.
Soft
Start Reset
It
is important that the soft start capacitor C602 be fully discharged when the
set is turned OFF. Turning Q648 OFF when the unit is turned OFF does this. This
removes the ground path from the relay, opening it up. It also allows current
from the Standby +5V to flow through the relay coil, through R621, to Q647/B.
This turns the Q647 ON and discharges C602 through R627. Q646 Backup will also be turned OFF when the
Power On line becomes HIGH.
Regulation
The
power supply is regulated by the control winding of PRT T603/7 and 8, in the
following manner:
An increase in voltage across the control winding will reduce the inductance of
the windings in T603, consequently increasing the converter frequency. When the
converter frequency increases, it moves further away from the optimum operating
frequency of T605 PIT, reducing the voltage at the secondary outputs. The
opposite occurs when the voltage across pins 7 and 8 decreases. A correction
voltage is produced by IC643/4, which varies inversely proportional to the 135V
line. Pin 7 of the transformer control winding is connected to the correction
voltage. The other leg of the control winding (pin 8) is connected to the
output from D603 Vcc Rectifier. The difference in the voltage across this
winding determines the frequency of the converter which regulates the +135 Volt
line as described in the previous sections.
Foldback
The
foldback circuit is a type of protection circuit that uses a winding on T605
PIT to monitor the current drawn by its secondary. This voltage is rectified
and called Vcc Rect. Q624 is set up with the Vcc Rectifier voltage input to the
emitter. Its base is connected to the Rectified +12 volt line from the
secondary side of the supply through D605 and R609. D605 is a zener diode whose
breakover voltage is 13 volts.
This circuit will protect against two failures. The first is a rise in the Vcc Rect.
This voltage is developed by the foldback winding of T605. This winding is used
as a current mirror. This means that the more current drawn on the secondary of
T605 PIT, the higher the voltage at T605/3.
When too much current is drawn from the secondary, Q624 would turn ON because
of the increase in voltage across R610. If this occurs, the latch and soft
start circuits will be activated. Soft start is activated to lower the output
supply voltage by increasing the switching frequency. The latch’s purpose is to
shut the supply down.
Secondly, if there were a loss of the +12 volt line then D605 would breakover.
This would cause sufficient current flow through R610 and Q624 would turn ON.
If this occurs, the latch and soft start circuits will be activated.
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