Philips A02U AA Service Manual page 19

5.8.5
Main Supply
1. Replace FET 7504 and zener 6505.
2. Disconnect the SSP panel.
3. Short B and E of TS7529, in order to put the Main Supply
in "on"-mode (TS7529 is blocking then).
Caution: To prevent that R3403 and TS7443 will be
damaged, first disable the HW-protection of the
deflection circuit. Therefore, short-circuit C2642 on the
LSP (diagram A4).
4. Attach a load of 500 ohm to the V_BAT capacitor C2515
(the supply can not work without a minimum load).
5. Use a variac, and slowly increase the V_MAINS. Measure
over sensing resistors R3514//15, if a nice sawtooth
voltage becomes available.
6. Also, measure the V_BAT. This may never exceed +141 V.
If it does, there is something wrong in the feedback circuitry
(e.g. regulator 7506).
Note: Be careful when measuring on the gate of FET TS7504.
This circuitry is very high ohmic and can easily be damaged
Table 5-3 Repair tips
Phenomenon
No picture, no LED.
No picture, LED blinking at 3 Hz.
No picture, LED blinking with code 8-8-8-
etc or 9-9-9-etc.
No picture, LED blinking with code 13-13-
13-etc.
No picture, no sound. Set is making
audible squeaking sound
No picture, no sound. Front LED works fine Supply does not work correctly.
No RC-reception. Front LED does not
echo RC-commands.
Relay (degaussing) is not audible, when
set is switched from "off" or "standby" to
"on".
Picture is rotated.
Picture is continuously switching "off" and
"on", showing heavy "switch" spots (set
does not go into protection).
Picture is not sharp.
Picture is distorted.
No menu, no OSD.
No Teletext.
Strange switch "off" behaviour
Various symptoms, due to missing local
supply voltage.
Service Modes, Error Codes, and Fault Finding
Possible Cause
Standby Supply defective.
Set is in protection due to various
causes. For error codes see error-
code list.
No communication on slow I2C- or
fast I2C-bus.
No communication on NVM-I2C
bus to the uP.
Supply is possibly in hiccup-mode,
which is audible via a squeaking
supply transformer.
uP circuitry or RC-receiver is
defective.
uP is not working correctly. When
line "DEGAUS" is low, the
degaussing must be activated.
Rotation circuitry (if present) on
diagram A5, or related supply to it,
malfunctions.
200 V is missing on CRT panel.
Focus is possibly mis-aligned or
SCAVEM-circuitry does not work
correctly.
Check video-path in Service Default
Mode.
Probably a defective uP (ADOC).
IC7730 defective or not powered.
TS7445 possibly defective.
An interrupted fuse, NFR-resistor or
connection.
(first connect ground to measuring equipment, than measure
the gate).
5.8.6
Frame Deflection
Caution: When the Frame Deflection circuitry is suspected,
one must be careful. Because there is a DC-voltage on the
frame deflection, the beam current could damage the CRT
neck, leading to a defective CRT.
To prevent this from happening, you must:
1. Interrupt the resistors 3403 and 3404 on the CRT panel
(diagram F), in order to remove the "filament" voltage from
the tube (no beam current, so no chance of destroying the
CRT).
2. Interrupt resistor 3403 on the LSP (diagram A4) to disable
the "SUP-ENABLE" line.
3. Measure with a multi-meter, or better with an oscilloscope,
the functionality of the Frame stage.
4. After you have found the cause, exchange the defective
component (e.g. TDA8177), and re-solder the interrupted
resistors.
Repair tip
Measure circuitry (see diagram A2). Start at test-point A19.When the Mains switch is "on", this voltage
must always be available.
You have no picture, so: read the error buffer via ComPair (error buffer is accessible when set is in
protection, ComPair-file will guide you to this). Read the blinking LED information via standard remote
command mute-06250x-ok. Or you read the error code sequence via standard remote command mute-
062500-ok. When you have found the error, check the circuitry related to the supply voltage and I2C-
communication or the circuitry that triggers the protection.
As processor cannot communicate with one of the 2 busses it the standby-LED spontaneously starts
blinking 8-8-8-etc or 9-9-9-etc... If in the error buffer somewhere is an error 8 or 9, these will have the
highest priority starting the mentioned blinking. Measure dependent of the error on the I2C-bus which
device is loading the bus (use the I2C-overview)
As the uP cannot communicate with the NVM I2C bus, it spontaneously starts blinking 13-13-13-etc. Note:
when there is no access to the NVM, a lot of picture setting can go wrong.
Possible causes: V_BAT is shorted (caused by short circuited line transistor 7421), the sound winding is
shorted (amplifier is shorting the power supply lines), or D6514 is shorted (due to a too high V_BAT).
Remove excessive load, to see what causes the failure, or check feedback circuit. See repair tip "Main
Power Supply" (supply needs a minimal load).
If e.g. V_BAT is only about 90 V, it is possible that the regulator IC (7506) is defective.
In case the set does react on a local keyboard operation, you must check the RC-receiver circuitry
(diagram J).
Check RESET-circuitry (IC7581 on diagram B11). Check the level on line "DEGAUS" when you switch the
set "on". Signal must be low initially and go to high after approx. 12 s.
Measure test points on diagram A5.
Probably a bad connection from LSP connector 1424 to CRT connector 1424 (diagram F), or an
interruption of the 200 V supplies line (e.g. R3341 on circuit F1 is interrupted).
Re-align the "FOCUS" potmeter on the Line Output Transformer, or check the SCAVEM circuitry on the
CRT-panel (diagram F). It is also possible that the DAF circuitry is defective (see diagram I). Check the
V_dc values.
Investigate whether there is an error code present in the error buffer. In case there is one, check the I2C-
bus and/or supply lines (see overview supply lines). Measure and check signal path Tuner-MPIF-ADOC-
RGB amplifier. In case it is a geometry issue, check on diagram A4 opto-coupler 7482, OpAmps 7440/
7450 and the Frame circuitry alignments or a possible corrupted NVM (IC7525 on diagram B11).
Check circuitry around IC7730 on diagram B13.
Check, with a multi-meter, whether transistor TS7445 is well functioning. (diagram A3).
When no symptom or error code leads you to a specific circuitry, use the supply lines overview (see supply
lines overview), for a quick scan of all supply lines.
A02U AA 5. EN 19