Philips 32PHH4100 faulty power supply (dropping voltage)

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

I'll now try pulling them out and measuring them off-board

They are fine: 3.3 meg-ohm - measured and confirmed.

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Is R9146 = 0 ohms as should be. It looks OK in the photo but?

You also said that when you switch on the 12V supply is there and then starts falling. What is the voltage across pins 3 & 4 of U9102 when you initially switch on and after the 12V output supply drops.

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Is R9146 = 0 ohms as should be. It looks OK in the photo but?

You also said that when you switch on the 12V supply is there and then starts falling. What is the voltage across pins 3 & 4 of U9102 when you initially switch on and after the 12V output supply drops.

Yes that jumper resistor is 0 ohms. Let's clarify what happens to the 12v output: when the board is plugged in, it starts off at around 5v and slowly works itself up to around 11.5 and then stays there until the output is loaded. When loaded, it goes down to around 7.5. When the load is removed, it slowly goes back up to 11v.
I believe you meant U9101 in your previous reply, not 9012. If so, you want me to measure between ground and the CS pin (3 and 4) ? I get nothing between GND (4) and CurrentSense (3)...

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

I did mean the Opto-isolator (U9102)to check that when the 12V was supplied to the output, that it was driving the led within U9102 and switching on the transistor which in turn would short C9124 (1nF) to ground.
I'm looking at page 59/150 of the manual given in the earlier post.

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

I did mean the Opto-isolator (U9102)to check that when the 12V was supplied to the output, that it was driving the led within U9102 and switching on the transistor which in turn would short C9124 (1nF) to ground.
I'm looking at page 59/150 of the manual given in the earlier post.

Oh, right....terribly sorry for the mess-up. I forgot the opto is treated as "U" as well. Still, I get absolutely nothing between its pins. However, on the LED side, I get around 1.8v on its terminals.

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

OK so nothing (0 Volts) between pins 3 & 4 would correct when it's switched on by the diode and 1.8V across Pins 1 & 2 would be ON.

Does the 1.8V remain between Pins 1 & 2 even when the output voltage falls.

[budm]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

BTW, what DCV do you have between two legs of C9116 or C9122?

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Guys, you're not gonna believe this but the TV is working....WTF ?! I didn't do anything else - just took that last measurement of the optocoupler and noticed the voltage on the output caps was slightly higher this time (12.02v) so I put the bulb on it and this time it remained on....tried it on the TV and it fired right up. I believe it's been working for about an hour now, even from cold start-ups. Hate it when things fix themselves out of the blue. Let's hope it actually stays this way, though this could be a false sense of achievement, because something is probably only working half the time and I got lucky :|

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

BTW, what DCV do you have between two legs of C9116 or C9122?

I get 18v now that the set is working (see my latest post), but even when it didn't I'd still get around 17 with no load and they would drop to about 12v from what I recall.

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

I would be tempted to take the voltage readings around the PF6003AS and note them on your schematic (& post) in the event that it plays up again.
Any possibility that the Opto has a poor solder joint?

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

I would be tempted to take the voltage readings around the PF6003AS and note them on your schematic (& post) in the event that it plays up again.
Any possibility that the Opto has a poor solder joint?

It's not the original one - I replaced it as one of the first things I tried, so I believe I did a good job on those joints. Might actually go in there with some solder again just to make sure....

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

OK, but the voltage readings with the set now running would be useful to others when checking around that IC.

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

OK, but the voltage readings with the set now running would be useful to others when checking around that IC.

Right, I'll probably do that on Monday because, as per usual, it's at work and I have the day off tomorrow

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Thanks

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Ok, back with some measurements on this suddenly-functional board as promised. Readings were taken with no load and nothing attached to the power supply.
Primary (GND is - of bridge rectifier or - leg of C9801):
-C9801: 330v (on a 230v mains supply)
-U9010: 11.5v on Pins 6 and 8 (VCC). 1.2v on Pin 1
-C9105: 12.5v (before diode D9106)
-C9102: 11.5 (VCC for U9010)
---------
Sec (GND is chassis GND unless otherwise noted)
-C9101, 9109 and 9121 (actual numbering of caps might differ from the schematic) - 12.5v
-U9102 (across its terminals): 1.2v
-C8616 and C8612 (LED output): 18.2v (driver off), 29-30v (driver on)
Let me know if I missed anything you wanted to know.....while the TV's still around, for I'll have to return it soon if it doesn't decide to crap out on me again

[Moreno83]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Maybe its a cracked solder somewhere? You probably measured something and applied pressure and now its working again.

Something thats broken does not fix itself

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Maybe its a cracked solder somewhere? You probably measured something and applied pressure and now its working again.

Something thats broken does not fix itself

Well ok, I DID change a couple of things, not just measured it and hay-ho it's working

[dick_barton]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Thanks for the reading which may prove to be extremely helpful to anyone else with this problem. Hope the set now behaves itself.

[Dannyx]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Thanks for the reading which may prove to be extremely helpful to anyone else with this problem. Hope the set now behaves itself.

Hopefully...it's been working fine for almost 2 days now, counting the time I turned it off to let it cool down to ensure it doesn't work only thanks to heat, so it should be fine

[CapLeaker]

Re: Philips 32PHH4100 faulty power supply (dropping voltage)

Things like that I keep for at least a week.