Philips 32PFL3403d/27 LCD NO POWER

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Sorry, I'll try to be less confusing in the future.

1. With AC power disconnected, measure the resistance between the point 'Live Gnd' and the point labeled 'Live Gnd?'. The resistance should be less than 1 ohm (I think you have already done this, but I'm trying to make sure my recollections are correct).There is no resistance

2. Hook up AC power and CAREFULLY measure the voltages from 'Live Gnd' (Or 'Live Gnd?' if they are connected) (black lead) to the positive terminal of the large cap161VDC, to the point 'Standby SMPS Vcc?'10.3V, and to the point 'Main SMPS Vcc?10.3v10.3'

3. Now connect the 3 volt supply from pin 6 (minus side) to pin 10 (plus side), hokk up AC power, and carefully make the same measurements as in step 2. To the positive terminal of the large cap161VDC, to the point 'Standby SMPS Vcc?'8.9V, and to the point 'Main SMPS Vcc?10.3v8.9'


The purpose of these tests are to determine if the voltage on the emitter of Q905 is high enough to start the main SMPS controller, and if the same control signal also turns on the PFC correction circuit.

PlainBill

I did this twice to be certain of the values.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

I did this twice to be certain of the values.

Thank you. Well, this proves my ability to multitask is severely lacking.

I REALLY have to apologize. I've screwed up badly. TechFab.fr has provided the service manual, and it even includes a schematic of the power supply. Perhaps that can provide some badly needed information. I'll get back to you tomorrow.

PlainBill

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

I have a few points for you to verify, and then PERHAPS we can come up with a rational answer. In one way, this is frustrating. In my experience, Philips Service Manuals have a great deal of information about the main board, virtually nothing about the power supply. This one is the opposite.

Configuration: Hook the boards together as they would be if the TV was in normal operation and use at least two mounting screws to hold each of them in place. Locate U152 on the main board; it should be close to the power input connector. Set your DMM to the 20V DC range.
Plug in AC power and measure the voltages on each of the pins of U152, using one of the mounting screws as Ground (the tab is electrically connected to the middle pin). If the pins are at the bottom, the voltages should be 0V, 5.1V, and 3.3V. Report the voltages.

Next, on the power supply, measure the voltages at IC905, pin 4 and CN902, pin 10. Report the voltages.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

I have a few points for you to verify, and then PERHAPS we can come up with a rational answer. In one way, this is frustrating. In my experience, Philips Service Manuals have a great deal of information about the main board, virtually nothing about the power supply. This one is the opposite.

Configuration: Hook the boards together as they would be if the TV was in normal operation and use at least two mounting screws to hold each of them in place. Locate U152 on the main board; it should be close to the power input connector. Set your DMM to the 20V DC range.
Plug in AC power and measure the voltages on each of the pins of U152, using one of the mounting screws as Ground (the tab is electrically connected to the middle pin). If the pins are at the bottom, the voltages should be 0V, 5.1V, and 3.3V. Report the voltages.if the pins are at the bottom, the voltages read: leftpin=0V, the middle pin =3.28V, the left pin is 5.13V

Next, on the power supply, measure the voltages at IC905, pin 4 68V and CN902, pin 10 2.1v . Report the voltages.

PlainBill

I wonder if we can find some info on that main board, perhaps a different service manual. I can find the number of that board.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

I wonder if we can find some info on that main board, perhaps a different service manual. I can find the number of that board.

That is a good idea.

In the meantime, I neglected to give proper instructions. IC905 is on the hot side of the supply, so you can't use chassis ground. Use
IC905, pin 3 as the ground point. I would like to see the voltage at IC905, pin 4 and each end of R947.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

That is a good idea.

In the meantime, I neglected to give proper instructions. IC905 is on the hot side of the supply, so you can't use chassis ground. Use
IC905, pin 3 as the ground point. I would like to see the voltage at IC905, pin 4 and each end of R947.

PlainBill

With pin 3 of IC905 as ground I get 9.1V across pin 4. I used the same ground (pin3) to measure the voltage on R947: 17.6 on one side and 17.4 on the other.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

With pin 3 of IC905 as ground I get 9.1V across pin 4. I used the same ground (pin3) to measure the voltage on R947: 17.6 on one side and 17.4 on the other.

Al right!!! At last some readings I can understand.

Earlier you had read the voltage at R947 as about 8 volts, much to low to start the main SMPS controller. The problem was that there was no load on the output of the standby SMPS. With the load presented by the main board's standby circuits the voltage at R947 went up to a reasonable value.

Earlier I had indicated I felt the voltage from the main board on CN902, pin 10 was too low. That pin must go high to turn on the main power supply. When you drove it high with a 3 volt supply, IC905 did turn on. Clearly, it is not turning on with a lower (2.2?) input voltage.

Conclusion: The power supply is OK, the main board is bad.

NOW, eBay auction # 250853694866 is for one of the boards at $62. The listing also includes a number of different TVs that use this board. That listing might be the starting point for a search for a Service Manual that has the schematic of the board.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, I'm not sure if the sevice manuals I found contain that same board. Hmm, do you think we will crack this one?

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, I'm not sure if the sevice manuals I found contain that same board. Hmm, do you think we will crack this one?

I'm not optimistic. For some reason Philips made a majot change in their service manuals. There are several possible reasons, including that there are very few replaceable parts on the main board (other than the LDO regulators).

Here are the economics as I see it. There's a 5 year old Philips plasma TV in my wife's office. That TV went out of production 4 years ago, and sold for $1600. The plasma panel and the support boards were purchased from Samsung; Philips designed the 'Small Signal Board' (main board) and audio amplifier. It included a self diagnostic function. If a $1600 TV failed, they wanted to give a tech a decent chance of repairing it by troubleshooting to the component level.

Now the technology is more mature. The main board in your TV is less than 1/3 the size of the SSB in the 5 year old plasma, and is more complex. But a 32" LCD TV sells for as low as $200. At that kind of a margin, most service shops would have to do a board replacement.

Now, we here are exceptional. Spending a couple of hours to find a shorted diode makes sense if it means we don't have to buy a $100 board. But the Techs Philips cares about don't care if schematics are available.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well I managed to find a more comprehensive manual, (14 MB PDF) too big to upload. Should I get you the web address?

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well I managed to find a more comprehensive manual, (14 MB PDF) too big to upload. Should I get you the web address?

Yes, please.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Yes, please.

PlainBill

You have to follow the link that is about in the middle of the page (below the listed models), that will take you to another screed to do the actual download.

I was able to get a bunch of manuals there. If this one isn't the right one, then there are others.

here is the link:

http://english.electronica-pt.com/el...hp?find=LC8.1U LA


let me know if you get it.

TTYL Mach1

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

You have to follow the link that is about in the middle of the page (below the listed models), that will take you to another screed to do the actual download.

I was able to get a bunch of manuals there. If this one isn't the right one, then there are others.

here is the link:

http://english.electronica-pt.com/el...hp?find=LC8.1U LA


let me know if you get it.

TTYL Mach1

It's downloading now. Thanks for the tip.

<EDIT>
Well, bad news, good news, bad news.

It was the wrong service manual.

HOWEVER, thanks to TechFab.fr, I now know the chassis number of your TV. Examining the manual he linked to, I realized a large number of pages were missing. Searching Elektrotanya, I found the complete service manual (two of them, actually).

But I'm going to be too busy to do much with them for a few days.

PlainBill

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Thanks for your patience. U500 is the standby processor. I'm going to have you check a few points on the board and see if we can figure out what is going on.

The first point to check is U500, pin 1 (U500 is the 44 pin square IC next to the RCA connectors). It should be at 3.3 volts (U500, pin 2 is Gnd). Next, check the voltage on U500, pin 43. Report the voltage. If it is below .5 volts, stop.

If everything is good so far, check the voltage at U500, pin 30. That drives the devices that drive pin 10 on the power supply.

And last, check the voltages on each end of R140. R140 is on the back side of the board.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Thanks for your patience. U500 is the standby processor. I'm going to have you check a few points on the board and see if we can figure out what is going on.

The first point to check is U500, pin 1 (U500 is the 44 pin square IC next to the RCA connectors). It should be at 3.3 volts (U500, pin 2 is Gnd) its 3.3V . Next, check the voltage on U500, pin 43. Report the voltageIt is also 3.3V. If it is below .5 volts, stop.

If everything is good so far, check the voltage at U500, pin 30 it is 0.05v practally nothing . That drives the devices that drive pin 10 on the power supply.

And last, check the voltages on each end of R140. R140 is on the back side of the board.

PlainBill

What should I use as ground for R140? Incidentally I measured 1.3V across the resistor. (end to end)

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

What should I use as ground for R140? Incidentally I measured 1.3V across the resistor. (end to end)

Use the negative lead of C505 (the thru-hole electrolytic cap on the top of the board in that area) for ground.

All of the readings look good. I'm going to have to examine the power supply schematic, the 1.2 volt drop across R140 seems to be excessive. Measure it, it should be 2.2K

PlainBill

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Update: I looked at the schematic, and the voltage drop across R140 IS excessive. The effective resistance of the input into pin 10 on the power supply should be in the order of 150K ohms.

I hope you still have your 3V 'power supply', and a 2.2K resistor handy. Hook one end of the 2.2K resistor to pin 10 of the power supply connector CN902, the other end to the positive lead of the 3V supply. Apply AC power to the supply and measure the voltage drop across the 2.2K resistor. Report it.

There are several components that can be responsible for the excessive load, one on the main board, two on the power supply. This will tell us where to look.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Update: I looked at the schematic, and the voltage drop across R140 IS excessive. The effective resistance of the input into pin 10 on the power supply should be in the order of 150K ohms.

I hope you still have your 3V 'power supply', and a 2.2K resistor handy. Hook one end of the 2.2K resistor to pin 10 of the power supply connector CN902, the other end to the positive lead of the 3V supply. Apply AC power to the supply and measure the voltage drop across the 2.2K resistor. Report it.

There are several components that can be responsible for the excessive load, one on the main board, two on the power supply. This will tell us where to look.

PlainBill

Well, I had to do some rigging, and this is what I did. I left everything connected, and tapped into the CN902 pin 6 for ground (the negative side for the power supply) and connected my 2.2k resistor to the (+ side)3v power supply, and tapped into pin 10. Then tested the voltage across the 2.2k with the ac power on by connecting the DMM on eiter side of the resistor. The reading is 0.57V

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, I had to do some rigging, and this is what I did. I left everything connected, and tapped into the CN902 pin 6 for ground (the negative side for the power supply) and connected my 2.2k resistor to the (+ side)3v power supply, and tapped into pin 10. Then tested the voltage across the 2.2k with the ac power on by connecting the DMM on eiter side of the resistor. The reading is 0.57V

I'm trying to get my head around this, but to me that .57 volt drop is excessive, so further tests will be necessary. These may be easier.

Connect the main board to the power supply, then hook up AC power. Measure these voltages across R931, R932, and R943 on the power supply. Those three resistors carry the loads on the STBY pin. HOPEFULLY only one of them will have a significant voltage drop. If that is the case, stop and report your results.

If all three showed a very low (less than .2 volt) drop, disconnect AC power, then isolate pin 10 of CN902 from the cable connecting the power supply to the main board. You can do that either by cutting the wire, or preferably, releasing that wire from the plug. Then hook up AC power and measure the voltage at CN100, pin 10 on the main board. If the main board is fine, you should read very close to 3.3 volts.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

I'm trying to get my head around this, but to me that .57 volt drop is excessive, so further tests will be necessary. These may be easier.

Connect the main board to the power supply, then hook up AC power. Measure these voltages across R931, R932, and R943 on the power supply. Those three resistors carry the loads on the STBY pin. HOPEFULLY only one of them will have a significant voltage drop. If that is the case, stop and report your results.

If all three showed a very low (less than .2 volt) drop, disconnect AC power, then isolate pin 10 of CN902 from the cable connecting the power supply to the main board. You can do that either by cutting the wire, or preferably, releasing that wire from the plug. Then hook up AC power and measure the voltage at CN100, pin 10 on the main board. If the main board is fine, you should read very close to 3.3 volts.

PlainBill

Sorry I was gone for a while....I didn't detect much of a voltage drop across R931,932 and 943. So I unplugged wire 10 from CN902, tested the voltage of #10 pin on CN100, (to pin 6 for gnd) with 2.1V.