Repair Tips - Philips FTL2.4E Service Manual

EN 20 5. FTL2.4E AA
This is done, because the interrupt on one of the inputs is
possibly caused either by a flash or by ESD. As a flash or ESD
can influence IC settings, the HIP, MSP, 3D Comb and wireless
module (not used in this set) are initialised again, to ensure the
normal picture and sound conditions of the TV.
8 V and 5 V protections: The microprocessor senses the
presence of the 8 V and 5 V (via the "+5V_CON" and
"+8V_CON" lines). If one (or both) of these voltages is (are) not
present, an error code is stored in the error buffer of the NVM,
and the TV is put in the protection mode.
Audio Supply protection: The OTC senses if the audio
module is in protection via IRQ-DIGITAL (pin 98 of OTC). If this
is the case, the OTC puts the TV in protection.
5.7.4 Hardware Protection
Short-circuiting the 3V3 supply from the DC/DC converter will
shut down the DC/DC converter. The absence of the 3V3
supply line is also sensed via I
protection above), this is useful if there is something wrong in
the detection circuit of the DC/DC converter.
Audio DC Protection: This protection occurs when there is a
DC voltage on the speakers. In that case, the Main Supply is
switched "off". The Stand-by Supply is still working.
Repair tip: If there is an audio DC protection (DC voltage on
your speakers), you will probably see error 18 blink. To be sure
this is an audio DC protection, disconnect the cable between
the SSB and the audio PWB and also the cable between the
Main Supply and the Audio PWB. If the TV starts up, it is very
likely that there is DC on the speakers. Check, and replace if
necessary, the audio amplifiers.
Note: 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 can not disappear through the
speakers).
5.8

Repair tips

5.8.1 3V3 Supply (DC/DC converter on the SSB)
As mentioned above, the DC/DC converter is switched "off"
when something goes wrong (detection of a missing 3V3
supply at one of the devices supplied by the 3V3). Because of
this, the TV goes to protection (I
is logged.
For further diagnoses, you need to overrule the I
put the TV in Service Default Mode by means of the solder
pads on the SSB (see figure "Service pads").
The DC/DC converter is still not working because it is switched
"off" by the 3V3_FAULT line (schematic B12). Now you have
some possibilities:
1. First, measure the impedance over diode 6U06. In normal
conditions, you should measure approximately 120 ohm (if
possible, verify this with another set). If the impedance is
much too low, do not try to start up the converter as
mentioned below. Remind that if FET 7U03 is short-
circuited, this will also influence your measurement.
2. Desolder coils 5U05 and 5U06, connect an external 3V3
supply at capacitor 2U23 (current limitation to 500 mA) and
a second external 3V3 supply at capacitor 2U31 (current
limitation to 800 mA). The normal working current of the
3V3_SIM line is approximately 400 mA and the normal
working current for the 3V3_DCDCFBX line is
approximately 700 mA. Therefore, if one of the currents
exceeds their nominal value you can determine in which
circuit the overload is situated. If the TV would start up and
you have normal picture, there is probably no overload but
a problem in the detection circuits.
Service Modes, Error Codes, and Fault Finding
2
C (see description Audio Supply
2
C protection). Error code "55"
2
C protection:
3. If you do not have two external power supplies, you can do
the following: Desolder coils 5U02, 5U03, and 5U04 (you
must desolder all three, otherwise the circuit could be
damaged), connect an external power supply of 3V3 at the
cathode of diode 6U06. Make sure to limit the current of this
external supply to approximately 1200 mA. If the supplied
current exceeds 1100 mA (approximately normal working
current) you can conclude that one of the devices supplied
by 3V3 is short-circuited.
4. Another possibility is to force the converter to start up by
short-circuiting (and keep short-circuited) resistor 3U25
(B12).
Caution: Be aware that this can damage the TV. Even if
you measure approximately 120 ohm over diode 6U06,
there can still be something wrong in the converter itself.
By short-circuiting resistor 3U25, the internal protection of
the converter is disabled.
5.8.2 Protections
Activating SDM via the "service pads" will overrule the
processor-controlled protections, but not the hardware
protections. This means, that the A/D-input protections (5 and
2
8 V) and the I C "not-acknowledging" info of FBX + EPLD + 3D
Comb and of the tuner are overruled.
Caution: When doing this, the service technician must know
what he is doing, as it could lead to damaging the TV.
Note: It can sometimes take up to half a minute before the TV
goes to protection!