[Philips TV] 47PFL5604H backlight/inverter

[budm]

Re: [Philips TV] 47PFL5604H backlight/inverter

I took some measurements with the PSU connected on AC.

On CN4 Connector i get no 3.3VSB.

IC901 (3BS3LJ)
Pin 7 (VCC) cycles between 11 and 17volts
Pin 4 (HV) is stable at 270 Volts

IC4 (DDA005)
Pin 2 (IN) starts from 21.6 Volts and falling with steady step (measured up to 20 Volts)
Pin 4 (OUT) is 0

On R916 close to IC901 i also get 11-17 Volts cycling.


Without AC connected :

On D908 close to IC901 i measure 0.062V in DMM diode mode, in both directions.
On D903 i measure 0.175V, the same with above.

Is IC4 my problem, since there is no VCC-ON voltage ?


Thank you in advance

Remove those suspect diodes that show bad in the circuit and test them off the board.
It sounds like the SMPS is cycling on and off which can be due to shorted circuit or bad startup/running cap.
Please upload the pictures of YOUR board also.
Is this the same EXACT board as OP?

[felix]

Re: [Philips TV] 47PFL5604H backlight/inverter

Remove those suspect diodes that show bad in the circuit and test them off the board.
It sounds like the SMPS is cycling on and off which can be due to shorted circuit or bad startup/running cap.
Please upload the pictures of YOUR board also.
Is this the same EXACT board as OP?

Hello budm! Thank you for your reply !

My power supply is the same as the OP, DPS-298CP-2A. The photos are attached.

I will measure the diodes off-board and come back with results.

Thank you again!

[felix]

Re: [Philips TV] 47PFL5604H backlight/inverter

I unsoldered with my hot air station all 4 diodes that gave a 0.031/0.062V measurement both ways.

All are in the range of 0.550-0.570V (DMM diode mode) and only one direction, whch means that they are ok.

[nomoresonys]

Re: [Philips TV] 47PFL5604H backlight/inverter

Replaced Q301A and Q301B (P10NK60ZFP) with P12NM50FP as didn't find exactly the same part. Also replaced R344 with 0.2ohm resistor.

Now when turning on it tries to strike few times and there is voltage spike of 40V on VCC and I hit overvoltage(>600v) beep on my multimeter on Q301A. Same overvoltage spikes I get on T301 input. Still backlight doesn't turn on. C731/C709/C734/C705/C808 are already replaced.

The burnt-out resistor indicates a short circuit of Q301a(type P6NK60ZFP), and resistor maybe goes defective when one of the capacitors C306A/C306B is no longer in order?

Ever get it sorted out?

[felix]

Re: [Philips TV] 47PFL5604H backlight/inverter

I unsoldered with my hot air station all 4 diodes that gave a 0.031/0.062V measurement both ways.

All are in the range of 0.550-0.570V (DMM diode mode) and only one direction, whch means that they are ok.

UPDATE:

I changed all THT caps and backlight caps except the large 450V/150uF and i somehow managed to get it working (tv signal,hdmi input etc).

After that it seems like it tries to power up (led blinking white) but then it powers off again.

Continuing the search, because the owner already bought a replacement TV, so i have plenty of time to troubleshoot (he wants it as a spare)

[OobabeloO]

Re: [Philips TV] 47PFL5604H backlight/inverter

Hello Felix,
did you manage to find the issue with the backlight ?
I'm facing a similar issue on my DPS-298CPA board : the TV will work for a given time, then the backlight will switch off and back, etc.. and then off until I restart the TV (cold boot).
I already changed all mosfet, the HT caps as the IC that drives the mosfets to solve an annoying clicking sound (and this was indeed the cure).
Regards,

[ydbeba]

Re: [Philips TV] 47PFL5604H backlight/inverter

Hello, I have quite a similar issue. No backlight I unsoldered HT caps C705, C731, C734 and C789. I found two of these bad, one is 10 pF and the other one is 20 pF.

The two OK are 33 pF

Unfortunately I did check which value those were, before unsoldering. Can anyone telle me
which is which. Board is DPS-298CP-2.

Thanks

[ydbeba]

Re: [Philips TV] 47PFL5604H backlight/inverter

Looking at the schematic, these caps are connected to HV1 and HV2. Looks like C789 should read C709.