Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

[penspinner]

Hello everyone,

a few days ago, I wanted to turn on my Philips 47PFL3605H/12 TV with the RC and was greeted with a nice and loud bang. So I opened up the TV and found that the IC905 (TNY277PN) had exploded with the drain pin being molten to a little metal blob. First thing I did was to change the part, however, I was not able to fix the problem this way.

There is still no voltage on the secondary side whatsoever. The only voltage I am able to measure so far is 310V DC (Coming from 230V AC in Germany, but should still be 395V???) on the big filter cap (C907), as well as from the drain to the source pin on IC905.

I checked a few other parts and they all seemed to be fine (ZD907, IC907, the other diodes around IC905). The only thing I saw with my eyes was that there seemed to be some debris around the solder points of the transformer T904. So I unsoldered that except for the primary side to check if the IC905 does anything. And it seems like it does not. I don't know which protection mechanism is kicking in, but something seems to be wrong somewhere in the always-on 5VSB circuit. The caps all look fine, but I haven't checked any of them yet.

Do any of you have any suggestions as to what I could try next?

Any advice would be greatly appreciated!

Thank you,
Felix

[tvtimmy]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Panasonic?Philips? Which one are you talking about?

[petehall347]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

check for shorted diodes and open/high resistors . also shorted caps . something is burned .
also check other secondary voltages

[jetadm123]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

With power disconnected, try a resistance check between +5VSB to ground to see if you have something shorted.

[budm]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Beside looking for shorts in the secondary without the load, did you check R962, OPTO IC907 E-C junction, snubber diode D914?
Right now the DCV on the main filter will be only around 330V and it will kick up to 395VDC when PS-ON is present to turn on the PFC Voltage booster and the 24V power supply circuits, but for that to happen, the STBY PS has to be working first because it supplies the switched VCC to run the PFC IC and the 24V SMPS IC.
You can run the board by itself without other boards connected.

[penspinner]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Hi and thank you all for your answers!

I checked the components you mentioned (R962, IC907, D914) and they all seem fine. I didn't take the resistor out of the board but it reads 46.8 Ohm where 47 are needed. The optocoupler I hooked up to a little test circuit and it does its job as well. and the diode, which I also left on the board, opens in the direction it's supposed to, while not letting through any current in reverse.

For now I completely took out the transformer T904, and when I measure the resistance between +5VSB and GND, however, my DMM shows an open circuit in the beginning. After a few seconds it drops to around 350kOhm, and slowly decreases for ~2 minutes until it reaches 22.4kOhm (which should be ok, looking at the value of R956+R957).

Oh and by the way: I have a DMM as well as an analogue oscilloscope in case that helps.

Any ideas what I should try next? My idea was to take the caps out of the board and check them with my oscilloscope (my DMM does not have any cap functions). Does that make any sense or is it useless?

And one last question: Does it make any sense to do measurements on components that are still soldered in? Or is the general way to go to unsolder every part, check it, and put it back in?

Thanks a lot!
Felix

[budm]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

I would report the DCV reading of each pin of that TNY SMPS IC so we can see if they are normal or not.

[penspinner]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

I measured the voltages from each pin to the source of the TNY IC. The readings are as follows:

Drain - Source: 310V
BP/M - Source: 5.78V
EN/UV - Source: 1.27V

These are all measured with the DMM set to DC mode.

[penspinner]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Hi everyone,

I'm sorry if I'm being impatient, but just to let you know, I still haven't fixed the issue and am still working on it.
What I did was to disconnect the 5VSB output part from the transformer output (while keeping the control loop intact of course). There is still no 5V output.

I then tried to measure the voltage on the secondary side of T904 (pin 9 - 7) with my oscilloscope and there is actually some output! Every second or so, there are some ~50kHz pulses that oscillate a little bit and then decay (if that's the word? )
The amplitude was only a few mV though. I posted 2 pictures of the signal, one of the single pulse, and one of the multiple pulses in a bigger time frame.

Any ideas what is happening here?

Thanks, Felix

[dick_barton]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

I'd agree with Petehall347. If the TNY blew up it's likely to have taken one or more of the diodes/zeners down with it.
ZD909, D904, ZD912, ZD908, D916, ZD907, Q915, Q918, Q902

[Agent24]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

See page 4 of datasheet about auto-restart function. That's probably what you're seeing. Quite possibly feedback circuit saw full line voltage when the IC shorted. So yeah, check all the semiconductors around there.

Did you check the rectifier diodes as well? D917?

With T904 out of circuit there is no path between 5vSB rail and GND through D917 so it won't tell you if D917 is bad.

[3sly]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Were you able to find the problem? Funny enough I have the EXACT same model, and I opened it up and it had the EXACT same chip blown :p.

[penspinner]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

Unfortunately no, but I still have the TV lying around, so if you find out anything it'd be great if you could tell me! I'll do the same of course.

[thoma]

Re: Philips 47PFL3605H/12 Power Supply Not Working (Not Even Standby)

TPM5.1ELA Chassis Philips

http://forum.iwenzo.de/topic.php?t=6...hlight=philips