PHILIPS 30W 8402 REPAIR TIPS

                                                               PHILIPS 30W 8402


PART-2


REPAIR TIPS

• The click sound of relay you here, when you switch ON the set, from standby or via AC powe switch at its front panel is from the degaussing circuitry.  It is not used for switching and Power supply, as done in MG-chassis.
• Where the circuitry was too crowded for service printing, find the correct location on the test point.
• A VERY LARGE PART OF 'LSP' IS 'HOT', SUCH AS:-
• The primary part of the standby supply.
• The whole main supply, except for secondary audio supply.
• All the deflection circuitry; notice that the deflection coil is 'Hot'.

PROTECTIONS

Activating SDM via 'service pads' will overrule the processor controlled protections; but not the hardware protections.  When doing this, service technician must know, what he is doing, as it could lead to damage the set.

The ARC-and or 'Bridgecoil' protection are harldly ever triggered, however:-

1. When suspected the 'ARC' protection, look for bad solder joints and smell.  By interrupting reisistor [3497], this problem is disabled.
2. When suspect the 'Bridgecoil' protection, which can also be due to a too wide picture amplitude, shorten 'G' and 'S' of the E/W MOSFET (7480).  This will disable the protection.  The set will now have minimal horizontal amplitude.  Re-align the horizontal amplitude in the 'SAM' menu and remove the G/S short of [TS 7480].

MAIN SUPPLY

• Replace FET 7504 and zener diode 6505.
• Disconnect SSP panel.
• Short 'B' and 'E' of TS7529, in order to put the main supply in ON-Mode, TS7529 is blocking then.
• NB:  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).
• Attach a load of 500 Ohm to the V-Bat capacitor C2525, because the supply cannot work without a minimum load.
• Use a variac, and slowly increase the V_Mains.  Measure the over sensing resistors R35154/15, if a nice sawtooth voltage becomes available. 
• Measure the V_Bat.  This may never exceed [+141V].  If it does, there fore is some thing wrong in the feedback circuitry. For example: voltage regulator 7506.
• Note:  Be careful when measuring the On Gate of [FET TS7504].  This circuitry is very high Ohmic, and can easily be damaged.  First connect the Ground to the measuring equipment, then measure the Gate.

FRAME DEFLECTION

When the frame deflection circuitry is suspected, must be very careful.  There is a DC voltage on the frame detection, the beam current could damage the CRT neck, leading to defective CRT.

To prevent this from happening:-

1. Interrupt the resistors 3403 and 3404 on the CRT panel, in order to remove the filament voltage to the CRT.
2. Interrupt resistor 3403 on the LSP, to disable the 'SUP-ENABLE' line.  
3. Measure the functionality of the Frame Stage with a good quality multimeter or Scope.
4. After the cause has been detected, exchange defective component [Eg: TDA 8177], and resolder the interrupted resistors.

REPAIR TIPS:

• No picture No LED => Standby supply defective = Measure the circuitry, Start at Test point  [A19].  When the Main switch is ON, this voltage must be available.
• No picture.  LED blinks at 3Hz => Set is in protection due to various causes. = Here you have no picture.  So read the error buffer via ComPair. ComPair fault finding process is described in one among former posts here in this blog.  Error buffer is accessible when the set is in protection.  Read the blinking LED information via standard remote control command [Mute-06250x-Ok].  Or read the error code sequence via standard remote command [Mute-062500-OK].  When found the error check the circuitry related to the supply voltage and [I2C]communication, or the circuitry that triggers the protection.
• No picture.  LED blinking with, code 8-8-8- etc; or 9-9-9- etc =>  As processor cannot communicate with one of the two buses the standby LED will start blinking 8-8-8-etc; or 9-9-9-etc...If in error buffer somewhere is an error [8] or [9].  These will have highest priority starting the mentioned blinking.  Measure dependent on error on the [I2C] bus which device is loading the bus. 
• No picture.  LED blinking with code 13-13-13- etc: => No communication on NVM-I2C bus to uP. = As the uP cannot communicate with the NVM I2C bus, it starts blinking 13-13-13-etc:-  When there is no access to NVM, a lot of picture setting can go wrong.
• No picture No sound.  Set is making audible sqeaking sound. => Supply is possibly in hiccup mode, which is audible via sqeaking supply transformer. = V_Bat is shorted.  Check transistor [7421] for short circuit.  The sound winding is shorted.  Amplifier is shorting the power supply lines.  Or  {D6514} is shorted.  Remove excessive load, to see what causes the failure or check feed back circuit.
• No picture. No sound.  Front LED works fine. => Supply does not work correctly. + If V_bat is only about 90V, it is possible that the regulator IC 7506 is defective.
• No remote control reception,  Front LED does not echo remote control commands =>  uP circuitry or remote control handset is defective. = In case, the set do not react on a local keyboard operation, You must check the remote control first, for its infrared emission.  How to check a remote control, have been discussed somewhere in this blog site itself.  have to check the infrared sensor inside the TV too. 
• Relay-Degaussing is not audible, when set is switched On from Standby to ON. =>  uP is not working correctly.  When Line Degaus is Low, the Degaussing must be activated. =  Check Reset circuitry.  Check the level on Line Degauss, when the set is switched ON.  Signal must be Low initially and go to higher after approx:12s.
• Picture is rotated. => rotation circuitry or related supply to it malfunctioning.  
• Picture continuously switching OFF and ON, showing heave switch spots.  Set do not go into protection. => 200V is missing on CRT panel. = A bad connection from LSP connector [1424], or an interruption of 200V supplies line.  Example; R3341 on circuit F1 is interrupted.
• Picture not sharp => Focus is possibly misaligned or SCAVEM-circuitry does not work correctly. =  Re-align the Focus Potmeter on the line output transformer. Check the SCAVEM circuitry on the CRT panel.  It is also possible that the DAF circutry is defective. Check V_Dc voltages.
• Picture is distorted => Check video path in service default mode =>  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.  Measure and check signal path Tuner-MPIF-ADOC-RGB amplifier.  In case it is a geometry issue, check opto-coupler [7482], OpAmps 7440/7450 and the Frame circuitry alignments or a possible corrupted NVM.
• No OSD  or Menu => Probably a defective uP [ADOC].
• No Teletext => IC7730 deective. = Check whether transistor TS7445 is functioning well.
• Strange Switch OFF behaviour => TS7445 possibly defective. 
• Various symptoms due to missing local supply voltage => An interrupted fuse, NFR resistor or connection. = When no symptom or error codes leads to a specific circuitry, use the supply lines overview for quick scan of all power supplies.

SOFTWARE UPGRADING

• In this chasis upgrade can be done via ComPair

End