Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

I hope I (or someone else) will get back to you tomorrow, cuz I wanna friggin' go to bed, it's midnight here

In 8 hours it's midnight here and that's usually when I work in it lol

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

I hope I (or someone else) will get back to you tomorrow, cuz I wanna friggin' go to bed, it's midnight here

Bump up, is anyone willing to continue helping me find out what's wrong with this power supply? I would just buy a new one, but there are none available.

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Ok, let's dig further. From what I recall, you said you're getting 15v where you should, but just for a quick refresher, let's go over some values again. You're saying that with 5v applied to the ON pin, you're not getting 400v on the main cap and the other rails don't come on either.

It's time to start checking the control circuitry which is where it gets rather difficult (lots of small parts): ensure the 4 optocouplers are not shorted and neither are transistors Q1703 and Q1401. Probably a bit confusing this, but I'll try to explain it to the best of my abilities (mind you, I'm not a pro - there are far more knowledgeable people around here). With the power off, obviously, first set your multimeter to continuity (beep) and probe each pair of pins on the optocouplers.

More theory: an optocoupler provides feedback across the "border line" between HOT and COLD. You can't have a simple piece of wire going from COLD back to HOT because there would be no isolation, so light is used instead. If you look closely, you'll notice the optocouplers are the only components allowed to cross from HOT to COLD (well, there may be others, but let's not dig into that). An opto. has an LED and a transistor inside. Neither of these 2 parts should be shorted. The LED is on the COLD side and the transistor is on the HOT side. The "base" for the transistor is the light coming from the LED. It's physically impossible for the two sides to short, because it's just light passing from one side to another, but the internal transistor CAN fail.....very unlikely, but I did have this problem once on a Vestel board.

So first make sure you haven't got a dead short in either side of the opto. which would make the meter beep (VERY unlikely, but must be checked). Then, set your meter to diode mode and probe the two pairs again in either direction - the LED on the cold side (because it's a diode at the end of the day) should only read in one direction or not read at all. Same for the transistor. If you notice the transistor side (HOT side) giving the same reading in either direction, lift up one side of the opto and check again, if you STILL get the same reading (typically a low value regardless of how you place the probes), the opto is bad and needs to be replaced as the transistor has shorted (STILL very unlikely, but due diligence.....this is what happened to that Vestel I mentioned earlier).

The two transistors Q1703 and Q1401 toggle those 15 volts ON/OFF to the large switching IC in the middle and also the PFC IC on the right. I believe somewhere around here is where the problem lies, because I'm not liking the behaviour of that PFC booster not going to 400v as it should. Grab meter, set to diode first, probe around pins (try different combinations). If it doesn't beep (VERY unlikely for a BJT to fail flat-out like that), go into diode mode and probe again, again looking for low values while trying various combinations of pins (ideally, you'd remove the transistor if it's not too troublesome). I wanted to cram as much info into one post as possible so you'd have stuff to do and not report back every 2 hours or so. This is getting increasingly more difficult to do over the internet

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Ok, let's dig further. From what I recall, you said you're getting 15v where you should, but just for a quick refresher, let's go over some values again. You're saying that with 5v applied to the ON pin, you're not getting 400v on the main cap and the other rails don't come on either.

It's time to start checking the control circuitry which is where it gets rather difficult (lots of small parts): ensure the 4 optocouplers are not shorted and neither are transistors Q1703 and Q1401. Probably a bit confusing this, but I'll try to explain it to the best of my abilities (mind you, I'm not a pro - there are far more knowledgeable people around here). With the power off, obviously, first set your multimeter to continuity (beep) and probe each pair of pins on the optocouplers.

More theory: an optocoupler provides feedback across the "border line" between HOT and COLD. You can't have a simple piece of wire going from COLD back to HOT because there would be no isolation, so light is used instead. If you look closely, you'll notice the optocouplers are the only components allowed to cross from HOT to COLD (well, there may be others, but let's not dig into that). An opto. has an LED and a transistor inside. Neither of these 2 parts should be shorted. The LED is on the COLD side and the transistor is on the HOT side. The "base" for the transistor is the light coming from the LED. It's physically impossible for the two sides to short, because it's just light passing from one side to another, but the internal transistor CAN fail.....very unlikely, but I did have this problem once on a Vestel board.

So first make sure you haven't got a dead short in either side of the opto. which would make the meter beep (VERY unlikely, but must be checked). Then, set your meter to diode mode and probe the two pairs again in either direction - the LED on the cold side (because it's a diode at the end of the day) should only read in one direction or not read at all. Same for the transistor. If you notice the transistor side (HOT side) giving the same reading in either direction, lift up one side of the opto and check again, if you STILL get the same reading (typically a low value regardless of how you place the probes), the opto is bad and needs to be replaced as the transistor has shorted (STILL very unlikely, but due diligence.....this is what happened to that Vestel I mentioned earlier).

The two transistors Q1703 and Q1401 toggle those 15 volts ON/OFF to the large switching IC in the middle and also the PFC IC on the right. I believe somewhere around here is where the problem lies, because I'm not liking the behaviour of that PFC booster not going to 400v as it should. Grab meter, set to diode first, probe around pins (try different combinations). If it doesn't beep (VERY unlikely for a BJT to fail flat-out like that), go into diode mode and probe again, again looking for low values while trying various combinations of pins (ideally, you'd remove the transistor if it's not too troublesome). I wanted to cram as much info into one post as possible so you'd have stuff to do and not report back every 2 hours or so. This is getting increasingly more difficult to do over the internet

Ok I had a go at this and the 4 optocouplers are not dead shorted and neither are transistors Q1703 and Q1401.

I checked the 4 optocouplers in diode mode and IC1704 and IC1202 which I assume are 2 of the 4 optocouplers you are speaking of seem suspect to me. They measure in both directions. IC1202 measures in both directions on the COLD side, its not the exact same measurement, but a low value in both directions and IC1704 measures in both directions on the HOT side AND COLD side its not the exact same measurement, but a low value in both directions.

I will test them out of circuit tomorrow as I don't have time at the moment to do that. the other two optocouplers seem ok.

I will report back my findings testing them out of circuit.

Thank you sir.

[Moreno83]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Why not get a repair kit and repair the powersupply? Ofcourse it is cool to find out what parts are defect. It is doing less then it did before right? Some parts blew?
The powersupply is available on Ebay between $60 and $100.

Repair kit is $17

https://www.ebay.com/sch/i.html?_fro...17P5F&_sacat=0

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Why not get a repair kit and repair the powersupply? Ofcourse it is cool to find out what parts are defect. It is doing less then it did before right? Some parts blew?
The powersupply is available on Ebay between $60 and $100.

Repair kit is $17

https://www.ebay.com/sch/i.html?_fro...17P5F&_sacat=0

Of course that would be the ideal solution, but I believe the OP is not only trying to save some money but also improve his knowledge and learn more, which is most worthy of praise. After all, this is what our wonderful community is all about

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Why not get a repair kit and repair the powersupply? Ofcourse it is cool to find out what parts are defect. It is doing less then it did before right? Some parts blew?
The powersupply is available on Ebay between $60 and $100.

Repair kit is $17

https://www.ebay.com/sch/i.html?_fro...17P5F&_sacat=0

Dannyx is correct, plus when I looked on ebay last it wasn't available which was last week I looked. You also have to remember that i'm in Canada and the ebay link you sent was from .com which is the american side and they will not ship to Canada. I also do have the repair kit for this power supply as I said above. I have almost replaced every part from the kit and we are still at the same result. Not every part is in the kit like for example the two parts I suspect may be bad its not in the kit. all that's left from the kit that I didn't install yet is a few diodes which I have tested all of them and none are shorted and a few resistors.

[Moreno83]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Ok my bad , i did not know you had the repair kit! Will read the thread back and see if i can help.

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Ok, let's dig further. From what I recall, you said you're getting 15v where you should, but just for a quick refresher, let's go over some values again. You're saying that with 5v applied to the ON pin, you're not getting 400v on the main cap and the other rails don't come on either.

It's time to start checking the control circuitry which is where it gets rather difficult (lots of small parts): ensure the 4 optocouplers are not shorted and neither are transistors Q1703 and Q1401. Probably a bit confusing this, but I'll try to explain it to the best of my abilities (mind you, I'm not a pro - there are far more knowledgeable people around here). With the power off, obviously, first set your multimeter to continuity (beep) and probe each pair of pins on the optocouplers.

More theory: an optocoupler provides feedback across the "border line" between HOT and COLD. You can't have a simple piece of wire going from COLD back to HOT because there would be no isolation, so light is used instead. If you look closely, you'll notice the optocouplers are the only components allowed to cross from HOT to COLD (well, there may be others, but let's not dig into that). An opto. has an LED and a transistor inside. Neither of these 2 parts should be shorted. The LED is on the COLD side and the transistor is on the HOT side. The "base" for the transistor is the light coming from the LED. It's physically impossible for the two sides to short, because it's just light passing from one side to another, but the internal transistor CAN fail.....very unlikely, but I did have this problem once on a Vestel board.

So first make sure you haven't got a dead short in either side of the opto. which would make the meter beep (VERY unlikely, but must be checked). Then, set your meter to diode mode and probe the two pairs again in either direction - the LED on the cold side (because it's a diode at the end of the day) should only read in one direction or not read at all. Same for the transistor. If you notice the transistor side (HOT side) giving the same reading in either direction, lift up one side of the opto and check again, if you STILL get the same reading (typically a low value regardless of how you place the probes), the opto is bad and needs to be replaced as the transistor has shorted (STILL very unlikely, but due diligence.....this is what happened to that Vestel I mentioned earlier).

The two transistors Q1703 and Q1401 toggle those 15 volts ON/OFF to the large switching IC in the middle and also the PFC IC on the right. I believe somewhere around here is where the problem lies, because I'm not liking the behaviour of that PFC booster not going to 400v as it should. Grab meter, set to diode first, probe around pins (try different combinations). If it doesn't beep (VERY unlikely for a BJT to fail flat-out like that), go into diode mode and probe again, again looking for low values while trying various combinations of pins (ideally, you'd remove the transistor if it's not too troublesome). I wanted to cram as much info into one post as possible so you'd have stuff to do and not report back every 2 hours or so. This is getting increasingly more difficult to do over the internet

Ok I had a go at this and the 4 optocouplers are not dead shorted and neither are transistors Q1703 and Q1401.

I checked the 4 optocouplers in diode mode and IC1704 and IC1202 which I assume are 2 of the 4 optocouplers you are speaking of seem suspect to me. They measure in both directions. IC1202 measures in both directions on the COLD side, its not the exact same measurement, but a low value in both directions and IC1704 measures in both directions on the HOT side AND COLD side its not the exact same measurement, but a low value in both directions.

Ok finally able to get back to this, sorry for the wait. I removed the two optocouplers I thought were suspect, but out of circuit they test fine just like the others. They do not measure in both directions. So those 4 optocouplers are not at fault. Where should I look now?

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

Ok I had a go at this and the 4 optocouplers are not dead shorted and neither are transistors Q1703 and Q1401.

I checked the 4 optocouplers in diode mode and IC1704 and IC1202 which I assume are 2 of the 4 optocouplers you are speaking of seem suspect to me. They measure in both directions. IC1202 measures in both directions on the COLD side, its not the exact same measurement, but a low value in both directions and IC1704 measures in both directions on the HOT side AND COLD side its not the exact same measurement, but a low value in both directions.

Ok finally able to get back to this, sorry for the wait. I removed the two optocouplers I thought were suspect, but out of circuit they test fine just like the others. They do not measure in both directions. So those 4 optocouplers are not at fault. Where should I look now?

ok while I was waiting for a response i replaced IC1702 the center IC chip and I get the same results. I officially replaced every single IC Chip on this board IC1201, IC1401 and IC1702 and same results. Where should I look now? Please advise.

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

I'm assuming you're getting the correct VCC on the appropriate pins of the two ICs (PFC and switching) right ? Pretty stumped myself at this point, must admit. The only thing that's crucial right now is to ensure the ICs get their VCC. Check their datasheet to find out which pin to measure (there may even be jumpers labeled on the board too, but check the datasheet for the PFC IC so as not to probe it randomly like last time). The schematic comes in really handy here. There are 2 large resistors in between the heatsinks in the middle. They should be of very low value (check with the schematic) so see if your meter beeps when you put the leads across them - it should.

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

To simplify things for you a bit: page 33 of the manual. IC1201 should have 16v on pin 4 VCC. IC1401 should have 15v on pin 12 (probably easier to probe C1402 instead so as not to try and stick the probe on the small pins of the IC since it can slip and cause a short). Lastly, IC1702 should have 15v on pin 14.

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

I'm assuming you're getting the correct VCC on the appropriate pins of the two ICs (PFC and switching) right ? Pretty stumped myself at this point, must admit. The only thing that's crucial right now is to ensure the ICs get their VCC. Check their datasheet to find out which pin to measure (there may even be jumpers labeled on the board too, but check the datasheet for the PFC IC so as not to probe it randomly like last time). The schematic comes in really handy here. There are 2 large resistors in between the heatsinks in the middle. They should be of very low value (check with the schematic) so see if your meter beeps when you put the leads across them - it should.

Ok finally back at this have many things on the go. I also have been collecting and restoring full sized arcade machines which I dictate some time to as well. Anyhow I can't seem to find the 2 large resistors in between the heatsinks in the middle that your speaking of. Would you happen to know what they are labeled on the board?

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

To simplify things for you a bit: page 33 of the manual. IC1201 should have 16v on pin 4 VCC. IC1401 should have 15v on pin 12 (probably easier to probe C1402 instead so as not to try and stick the probe on the small pins of the IC since it can slip and cause a short). Lastly, IC1702 should have 15v on pin 14.

I have completed all the testing above on the IC's. Here is what I get...

IC1702 = 14.90 V

IC1401 = 14.90 V

IC1201 = 15.75 V

Don't forget all these IC's have been replaced with brand new ones.

Please advise about what 2 large resistors you are speaking about above so I could test those.

Please advise what to check next.

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

There are 2 white blocks between the heatsinks. R1719 and R1720. Those are your resistors feeding the source pins of the switching MOSFETs. VERY unlikely they're bad, but due diligence......Repeat the process for R1604 which fulfills the same function for the PFC MOSFETs. Seems you're getting the correct voltages on those ICs, so the search is still on I'm afraid.

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

There are 2 white blocks between the heatsinks. R1719 and R1720. Those are your resistors feeding the source pins of the switching MOSFETs. VERY unlikely they're bad, but due diligence......Repeat the process for R1604 which fulfills the same function for the PFC MOSFETs. Seems you're getting the correct voltages on those ICs, so the search is still on I'm afraid.

Ok back at it again.

I checked R1719, R1720 and R1604 all resistors check out ok. All have a very low value and all cause the meeter to beep. What should I check next? Please advise.

[Dannyx]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

We need to take this from the top again since it's been a while and it's getting hard to keep track of what has happened: please report back on your readings on CN1801. You say you're getting 5v on AL+5v. This should be applied to pin 3 of CN1801, P-ON-H1 either directly or through a small value resistor (10 ohms or something if you're a bit reluctant to short the pins directly). IC1401, which you say you even replaced if memory serves, should get 15v on its VCC pin, which I believe it does if I recall. Still, the voltage on the main cap does not go up...this is what bugs me. An oscilloscope would immediately tell us whether the IC is pulsing the gates those two FETs (Q1601 and Q1602) as it should, but without one we'll have to do it the old fashioned way bit by bit.

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

We need to take this from the top again since it's been a while and it's getting hard to keep track of what has happened: please report back on your readings on CN1801. You say you're getting 5v on AL+5v. This should be applied to pin 3 of CN1801, P-ON-H1 either directly or through a small value resistor (10 ohms or something if you're a bit reluctant to short the pins directly). IC1401, which you say you even replaced if memory serves, should get 15v on its VCC pin, which I believe it does if I recall. Still, the voltage on the main cap does not go up...this is what bugs me. An oscilloscope would immediately tell us whether the IC is pulsing the gates those two FETs (Q1601 and Q1602) as it should, but without one we'll have to do it the old fashioned way bit by bit.

OK to recap...

CN1801 AL+5v = 4.3v (On the board it says AL+4.3v, but in the manual it's printed as AL+5v, so not sure which one is correct, but I am getting 4.3v on PIN 3 of CN1801.)

All other PINS other than the AL+4.3v are dead on CN1801 when connected to the main board inside the TV and when it's jumped on with a jumper wire out of the TV all other PINS measure very low like the 12V measures 1. something also the back light PINS from the other connectors which should be putting out 24v is very low at just 1.something volts.

So what I see so far is I have very low 12v and 24v on this set and the the main filter cap is low.

IC1401 = 14.90v (And yes it has been replaced and Still, the voltage on the main cap does not go up.)

Unfortunately I don't own an oscilloscope.

What Should I check next, please advise, thank you.

[dskall]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

What was voltage across main cap?

[sfernandes]

Re: Philips 55PFL3907/F7 Dead, No Standby LED, Nothing, Please Help

What was voltage across main cap?

347.0 Volts