Service Modes, Error Codes, and Fault Finding
EN 42 Q528.1A LA5.
5.8.3 CSM
When you activate CSM and there is a USB stick connected to
the TV, the software will dump the complete CSM content to the
USB stick. The file (Csm.txt) will be saved in the root of your
USB stick. If this mechanism works you can conclude that a
large part of the operating system is already working (MIPS,
USB...)
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 cord”, presuming that the standby microprocessor is
operational.
• If the input voltage of DC-DC converters is around 12.7V
(measured on decoupling capacitors 2U03/2U93/2U6S
and 2U6R) and the enable signals are “low” (active) then
the output voltages should have their normal values. +12V
and +5V-POD supplies start-up first (enabled by POD-
MODE signal from the standby microprocessor). There is a
supplementary condition for +12V to start-up: if +5V-POD
does not start up due to a local defect, then +12V will not
be available as well. +5V-ON supply is enabled by the ON-
MODE signal (coming also from the standby
microprocessor) and is coming up a little bit later (20 ms)
due to the slower rise time needed to charge the USB
decoupling capacitor 2N31. +1V2 supply starts-up when
+12V appears, then at least 100 ms later, +1V8, +2V5 and
+3V3 will be activated via the ENABLE-3V3 signal from the
standby microprocessor. If +12V value is less than 10 V
then the last enumerated voltages will not show-up due to
the under-voltage detection circuit 6U10 + 7U10 and
surrounding components. Furthermore, if +12V is less than
8V then also +1V2 will not be available. The third DC-DC
convertor that delivers +1V4 out of +12V is started up when
the ENABLE-1V2 becomes active (low) and +12V is
present. The +Vtun generator (present only for the
analogue version of China platforms) will generate +33V
for the analogue tuner as soon as the 12V/3.3V DC-DC
converter will start to operate.
• The consumption of controller IC 7U00 is around 19 mA
(that means almost 200 mV drop voltage across resistor
3U01) and the consumption of controller IC 7U64 is around
12 mA.
• 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 stabiliser 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 +1V8 and +2V5 supply voltages are obtained via linear
stabilizer made with discrete components that can deliver
a lot of current, therefore in case +1V8 or +2V5 are short-
circuited to GND then +3V3 will not have the normal value
but much less.
• The SUPPLY-FAULT signal (active low) is an internal
protection (error 9) of the DC-DC convertor and will occur
if the output voltage of any DC-DC convertor is out of limits
(10% of the normal value).
Fault Finding
• Symptom: +1V2 not present (even for a short while
~10 ms)
1. Check 12 V availability (resistor 3U01, MOS-FETs
7U03 and 7U08), value of +12 V, +12 V switch (7U14
+ 7U16 and surrounding components) and +5V-POD.
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
5U02.
4. Check the over-current detection circuit (2U20 or 3U40
interrupted).
• Symptom: +1V4 not present (even for a short while
~10ms) while +12V is okay (also across input capacitors
2U6S and 2U6R).
1. Check resistor 3U7B and power MOS-FETs 7U61-1/2
2. Check the voltage on pin 4 (4 V)
3. Check enable signal ENABLE-1V2 (active “low”)
4. Check for +1V4 output voltage short-circuit to GND that
can generate pulsed over-currents 7...10 A through coil
5U60
5. Check the over-current detection reference(2U65 +
3U7C) and the boot components (2U66 + 6U60).
•
Symptom: +1V2 present for about 100ms, +1V8, +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 +1V8) that can generate pulsed over-
currents 7...10 A through coil 5U01,
5. Check the over-current detection circuit (2U18 or 3U31
interrupted).
• Symptom: +1V2 OK, +2V5 and +3V3 present for about
100 ms. Possible cause: SUPPLY-FAULT line stays “low”
even though the +3V3 and +1V2 is available - the standby
microprocessor is detecting that and switching “off” all
supply voltages.
1. Check the drop voltage across resistor 3U01 or 3U7B
(they could be too high, meaning a defective controller
IC or MOS-FETs),
2. Check if the boost voltage on pin 4 of controller IC
7U00 is less than 14 V (should be 19 V),
3. Check if +1V2 or +3V3 are higher than their normal
values - that can be due to defective DC feedback of
the respective DC-DC convertor (ex. 3U47, 3U77,
3U7L, 3U7J or 3U70).
• Symptom: +1V2, +1V4, +1V8, +2V5 or +3V3 shows a high
level of ripple voltage (audible noise can come from the
filtering coils 5U01, 5U02 or 5U60). Possible cause:
instability of the frequency and/or duty cycle of a DC-DC
converter or stabilizer.
1. Check the resistor 3U32 and 3U7D, capacitors 2U17
and 2U19, input and output decoupling capacitors.
2. Check a.c. feedback circuits
(2U23+2U24+3U55+3U63 for +1V2,
2U6D+2U6E+2U6G+3U6A+3U7E for +1V4 and
2U07+2U08+3U17+3U24 for +3V3), compensation
capacitors 2U25, 2U34, 2U36, 2U37, 2U40, 2U43,
2U68 and 2U6B.
• Symptom: +1V2, +1V4, +2V5 and +3V3 ok, no +Vtun
(analogue sets only). Possible cause: the “+VTUN
GENERATOR” circuit (7U24+7U26+surroundings
components) is defective: check transistor 7U24 (it has to
have gate voltage pulses of about 10 V amplitude and drain
voltage pulses of about 35 V amplitude) and surroundings
components. A high consumption (more than 6 mA) from
+Vtun voltage can cause also +Vtun voltage to be too low
or zero.
Note: when a pair of power MOSFETs(7U01+7U06,
7U03+7U08 or 7U61-1/2) becomes defective the controller IC
7U00 or 7U64 should be replaced as well.
To Next Page