Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Okay, so I connected +5V and S/B wire (PSon) via 1k resistor, and the voltage readings on CN903 connector are:

Still no voltage on +12V and +24V rails.
S/B voltage fluctuates; +4.7V and then gradually falls to +2.1V in 3-4 seconds, then rises back to +4.7V, stays still at +4.7V for a second or two, and then cycles again.
+5V voltage fluctuates as S/B voltage, of course.

I also connected +5V and ENA (BLon) with another 1k resistor, nothing changed.

It seems to me that I wasn't able to start this PSU alone by simply connecting the standby voltage back to the S/B.

Anyway, voltage on main filter cap (C907) is 312V.
I also measured VCC on IC901 (NCP1271D65R2G), VCC on IC902 (FAN6961SZ), voltage on pin 4 IC905 (TNY277PN-TL).

VCC on pin 6 IC901 = 4.26V (MB connected), 0.38V (MB disconnected), 1.54V (5V-S/B bridge).
VCC on pin 8 IC902 = 4.22V (mb connected), 0.38V (MB disconnected), 1.53V (5V-S/B bridge).
Pin 4 IC905 = 289V (MB connected), 312V (5v-S/B bridge).

Voltages on IC904 (EL817MA):
pin 1 = 4.07V
pin 2 = 5.20V
pin 4 = 0.08-0.12V.

D910 diode is fine, I desoldered and tested it.
I also tested motherboard, both U7003 and u7005 give stable 3V3SB all the time MB is connected, so I don't think MB is an issue here.

Please do note that I attached the diagram of PSU, I apologize for not doing it immediately.

Diagram od MB: https://datasheetspdf.com/pdf-file/1...lips/TPM6.1E/1

[budm]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Check the DCV between the two legs of the main filter cap when TV is turned on to see if you do have 380 ~ 400VDC PFC Boosted Voltage or not.
If not then you need to find out if the PFC IC has the switched VCC for it to run or not.

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Q902 looks fine. All caps look OK, there in no visible damage on any of the components.

Top of C922 is also looking good.

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Is the top of Q902 blown off?
C922 looks odd in your photo but it could just be a distortion in the photo.

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Are you certain the diode is shorted. Have you measured it out of circuit?
With the mainboard disconnected from the power supply use a 1K resistor between +5V and S/B then check the voltages again

I measured it in the circuit. I'll do that, thanks for the help!

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Are you certain the diode is shorted. Have you measured it out of circuit?
With the mainboard disconnected from the power supply use a 1K resistor between +5V and S/B then check the voltages again

[DrOetker]

I'm trying to fix my grandpa's TV - Philips 42PFL3606H/58 (TPM6.1E). It was working normally up until now, he said that while he was watching the TV at first the display went off, and after around 30 minutes, he lost the sound also. He tried to turn it on, but it wouldn't turn on anymore.

While plugged in it draws 9.7W, there is no red and green lights. While pressing the remote (power button, prog +-, etc.) or the buttons located on the device, it reacts and the red light blinks after the keypress. After pressing the power button, total power consumption falls to 0.1W, and after pressing it once again, it raises again to 9.7W.

I checked the voltages on CN903 (both before and after pressing pwr button and then after disconnecting mainboard) they are as following:

MB plugged in(9.7W) /// after pressing pwr btn(0.1W) /// MB disconnected (0.1W)
ENA -- 5.10V /// 0.05V /// 0.00V
DIM -- 2.68V /// 0.08V /// 0.00V
12V -- 0.28V /// 0.00V /// 0.00V
24V -- 0.00V /// 0.00V /// 0.00V
S/B -- 3.26V /// 0.08V /// 0.00V
5V -- 5.19V /// 4.71V /// 4.70V

PSU: 715G4802-P01-H20-003H
MB: 715G4609-M3A-000-005X

I noticed a few things... While plugging in the power cable, i can see a tiny spark on SG902 for a moment. No clicking sounds, blue LED on the back of the PSU doesn't turn on at all. Diode D910 is shorted. Voltage on C946 is 8.19V, and on C907 315V. There is no excessive heat generated anywhere on the MB, processor is mildly warm on the touch.

I'm trying to narrow down the fault.
Any help would be greatly appreciated.