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EN 28
5.
EJ3.0U PA
5.7
Protections
5.7.1
Software Protections
Most of the protections and errors use either the stand-by
microprocessor or the VIPER controller as detection device.
Since in these cases, checking of observers, polling of ADCs,
filtering of input values are all heavily software based, these
protections are referred to as software protections.
There are several types of software related protections, solving
a variety of fault conditions:
•
Protections related to supplies: check of the 12V, +5V,
+8V6, +1.2V, +2.5V and +3.3V.
•
Protections related to breakdown of the safety check
mechanism. E.g. since a lot of protection detections are
done by means of the VIPER, failing of the VIPER
communication will have to initiate a protection mode since
safety cannot be guaranteed anymore.
Remark on the Supply Errors
The detection of a supply dip or supply loss during the normal
playing of the set does not lead to a protection, but to a cold
reboot of the set.
Protections during Start-up
During TV start-up, some voltages and IC observers are
actively monitored to be able to optimize the start-up speed,
and to assure good operation of all components. If these
monitors do not respond in a defined way, this indicates a
malfunction of the system and leads to a protection. As the
observers are only used during start-up, they are described in
the start-up flow in detail (see paragraph "Stepwise Start-up").
5.7.2
Hardware Protections
There is one hardware protection in this chassis: "Audio DC
Protection". This protection occurs when there is a DC voltage
on the speakers. In that case the main supply is switched
"OFF", but the stand-by supply is still working.
Repair Tip
•
It is also possible that you have an audio DC protection
because of an interruption in one or both speakers (the DC
voltage that is still on the circuit cannot disappear through
the speakers).
5.8
Fault Finding and Repair Tips
Read also paragraph "Error Codes" - "Extra Info".
5.8.1
Exit "Factory Mode"
When an "F" is displayed in the screen's right corner, this
means that the set is in "Factory" mode, and it normally
happens after a new SSB has been mounted.
To exit this mode, push the "VOLUME minus" button on the
TV's keyboard control for 5 seconds and restart the set
5.8.2
MPIF
Important things to make the MPIF work:
•
Supply.
•
Clock signal from the AVIP.
2
•
I
C from the VIPER.
5.8.3
AVIP
Important things to make the AVIP work:
•
Supplies.
•
Clock signal from the VIPER.
2
•
I
C from the VIPER (error 29 and 31).
Service Modes, Error Codes, and Fault Finding
5.8.4
DC/DC Converter
Introduction
•
The best way to find a failure in the DC/DC converters is to
check their starting-up sequence at power "ON" via the
Mains/AC Power cord, presuming that the Stand-by
Processor is operational.
•
If the input voltage of the DC/DC converters is around 12 V
(measured on the decoupling capacitors 2U17/2U25/
2U45) and the ENABLE signals are "low" (active), then the
output voltages should have their normal values.
•
First, the Stand-by Processor activates the +1V2 supply
(via ENABLE-1V2).
•
Then, after this voltage becomes present and is detected
OK (about 100 ms), the other two voltages (+2V5 and
+3V3) will be activated (via ENABLE-3V3).
•
The current consumption of controller IC 7U00 is around 20
mA (that means around 200 mV voltage drop across
resistor 3U22).
•
The current capability of DC/DC converters is quite high
(short-circuit current is 7 to 10 A), therefore if there is a
linear integrated stabilizer that, for example delivers 1.8V
from +3V3 with its output overloaded, the +3V3 stays
usually at its normal value even though the consumption
from +3V3 increases significantly.
•
The +2V5 supply voltage is obtained via a linear stabilizer
made with discrete components that can deliver a lot of
current. Therefore, in case +2V5 (or +2V5D) is short-
circuited to GND, the +3V3 will not have the normal value
but much less.
•
The supply voltage +12VSW is protected for over-currents
by fuse 1U04.
Fault Finding
•
Symptom: +1V2, +2V5, and +3V3 not present (even for a
short while ~10ms).
1. Check 12V availability (fuse 1U01, resistor 3U22,
power MOSFETs) and enable signal ENABLE-1V2
(active low).
2. Check the voltage on pin 9 (1.5 V).
3. Check for +1V2 output voltage short-circuit to GND that
can generate pulsed over-currents 7-10 A through coil
5U03.
4. Check the over-current detection circuit (2U12 or 3U97
interrupted).
•
Symptom: +1V2 present for about 100 ms. Supplies +2V5
and +3V3 not rising.
1. Check the ENABLE-3V3 signal (active "low").
2. Check the voltage on pin 8 (1.5 V).
3. Check the under-voltage detection circuit (the voltage
on collector of transistor 7U10-1 should be less than
0.8 V).
4. Check for output voltages short-circuits to GND (+3V3,
+2V5 and +2V5D) that generate pulsed over-currents
of 7-10 A through coil 5U00.
5. Check the over-current detection circuit (2U18 or 3U83
interrupted).
•
Symptom: +1V2 OK, but +2V5 and +3V3 present for about
100 ms. Cause: The SUPPLY-FAULT line stays "low"
even though the +3V3 and +1V2 is available. The Stand-by
Processor is detecting that and switches all supply
voltages "OFF".
1. Check the drop voltage across resistor 3U22 (this
could be too high)
2. Check if the +1V2 or +3V3 are higher than their normal
values. This can be due to defective DC feedback of
the respective DC/DC converter (3U18 or 3UA7).
•
Symptom: +1V2, +2V5, and +3V3 look okay, except the
ripple voltage is increased (audible noise can come from
the filtering coils 5U00 or 5U03).
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