Service Modes, Error Codes, and Fault Finding
5.
5.6
The Blinking LED Procedure
Via this procedure, you can make the contents of the error
buffer visible via the front LED. This is especially useful when
there is no picture.
When the SDM is entered, the LED will blink the contents of the
error-buffer.
Error-codes
≥
10 are shown as follows:
–
a long blink of 750 ms (which is an indication of the decimal
digit),
–
a pause of 1.5 s,
–
n short blinks (n = 1 - 9),
–
when all the error-codes are displayed, the sequence
finishes with a LED blink of 3 s.,
–
the sequence starts again.
Example of error buffer:
12 9 6 0 0
After entering SDM:
–
1 long blink of 750 ms followed by a pause of 1.5 s,
–
2 short blinks followed by a pause of 3 s,
–
9 short blinks followed by a pause of 3 s,
–
6 short blinks followed by a pause of 3 s,
–
1 long blink of 3 s to finish the sequence,
–
the sequence starts again.
5.7
Protections
If a fault situation is detected an error code will be generated
and if necessary, the set will be put in the protection mode.
Blinking of the red LED at a frequency of 3 Hz indicates the
protection mode. In some error cases, the microprocessor
does not put the set in the protection mode. The error codes of
the error buffer can be read via the service menu (SAM), the
blinking LED procedure or via ComPair. The DST diagnose
functionality will force the set into the Service-standby, which is
similar to the usual standby mode, however the microprocessor
has to remain in normal operation completely.
To get a quick diagnosis the chassis has three service modes
implemented:
•
The Customer Service Mode (CSM).
•
The Service Default Mode (SDM). Start-up of the set in a
predefined way.
•
The Service Alignment Mode (SAM). Adjustment of the set
via a menu and with the help of test patterns.
See for a detailed description Chapter 9 paragraphs Deflection
and Power Supply.
5.8
Repair Tips
Below some failure symptoms are given, followed by a repair
tip.
•
Set is dead and makes hiccuping sound
‘MainSupply’ is available. Hiccuping stops when de-
soldering L5561, meaning that problem is in the
‘MainSupply’ load. No output voltages at LOT, no
horizontal deflection. Reason: line transistor 7402 is
defective.
•
Set is dead, and makes no sound
Check power supply IC7520. Result: voltage at pins 1, 3, 4,
5 and 6 are about 180 V and pin 8 is 0 V. The reason why
the voltage on these pins is so high is because the output
driver (pin 6) has an open load. That is why MOSFET
TS7521 is not able to switch. Reason: feedback resistor
3523 is defective.
Caution:
be careful measuring on the
gate of TS7521; circuitry is very high ohmic and can easily
be damaged! (first connect ground to measuring
equipment, than the gate).
•
Set is in hiccup mode and shuts down after 8 s.
Blinking LED (set in SDM mode) indicates error 5. As it is
unlikely that
µ
P ‘POR’ and ‘+8V protection’ happen at the
same time, measure the ‘+8V’. If this voltage is missing,
check transistor TS7408.
•
Set is non-stop in hiccup mode
Set is in over current mode; check the secondary sensing
(opto coupler 7515) and the ‘MainSupply’ voltage. Signal
‘Stdby_con’ must be logic low under normal operation
conditions and goes to high (3.3 V) under standby and fault
conditions.
•
Set turns on, but without picture and sound
The screen shows snow, but OSD and other menus are
okay. Blinking LED procedure indicates error 10, so
problem is expected in the tuner (pos. 1000). Check
presence of supply voltages. As ‘5V’ at pin 6 and
7 are okay, ‘VT_supply’ at pin 9 is missing. Conclusion:
resistor 3428 is defective.
•
Set turns on, but with a half screen at the bottom.
Sound is okay
Blinking LED (set in SDM mode) indicates error 2. Check
‘13V’, ‘+5V’ and ‘+50V’. If they are okay, problem
is expected in the vertical amplifier IC7471. Measure with
a scope the waveform on pin 17 of the UOC. Measure also
at pin 1 of IC7471. If here the signal is missing, a defective
resistor R3244 causes the problem.
