Philips 32PFL3403d/27 LCD NO POWER

[rmoody]

Re: Philips 32PFL3403d/27 LCD NO POWER

There is nothing wrong with Philips TVs. They aren't the top of the line, but at least documentation is available for them, unlike the Vizios and the private label junk coming out of China. PlainBill

I agree, My personal tv of about 4 years is a philips and I haven't had trouble yet. I haven't been messing with tv's very long but from what i've seen, any lcd/plasma will can/will have a problem within 4-6 years of operation. Some less some more.

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

There is nothing wrong with Philips TVs. They aren't the top of the line, but at least documentation is available for them, unlike the Vizios and the private label junk coming out of China.

IC903 provides feedback for the SMPS controller, so IC905 is handling the On/Off control.

This is going to take a while.

Step 1: Check the resistance from J923 to pin 3 of IC905.

Step 2: To be determined. I'm having problems tracing a link from Pin 6 of IC901 to pin 4 of IC905.

PlainBill

Well, I was tinkering around myself tooking for that trace and I happened upon something that seems odd look at the attached picture. I've circled in red the area of concern, namely R933 seems to be missing. I was tracing from Pin 6 of IC901 and noticed the skip. Tell me what you think.

Oh and by the way, there is no resistance from J923 to Pin3 of IC905.

[rmoody]

Re: Philips 32PFL3403d/27 LCD NO POWER

That doesn't look like there's ever been a Resistor there so I wouldn't worry about that. Sure wouldn't want to connect a circuit that's not supposed to be connected.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, I was tinkering around myself tooking for that trace and I happened upon something that seems odd look at the attached picture. I've circled in red the area of concern, namely R933 seems to be missing. I was tracing from Pin 6 of IC901 and noticed the skip. Tell me what you think.

Oh and by the way, there is no resistance from J923 to Pin3 of IC905.

Moody is correct. That sort of thing is common. One possibility is it was to accommodate a different version of the supply, or to use a different SMPS controller.

Darn!!! C'est la vie. But I'm not going to let you off that easy.

I've marked three points with blue dots. Starting with IC905, pin 3, what are the resistances to the other two points?

I've marked three points with red dots. Are any of them connected to IC901, pin 6?

And I've marked 6 semiconductors with yellow circles. Check these for shorts. What are the marking codes on the two transistors?

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, this is how one is to learn, respectfully from guys like you. So I've tested the IC905 to the blue dots: 0.0 ohms to the dot left (J923) and 0.0 oms to the dot on the right.

The red dot on the right is connected to pin 6 on IC901, the lower/middle dot (R912) is also connected and the dot at C911 is NOT connected.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, this is how one is to learn, respectfully from guys like you. So I've tested the IC905 to the blue dots: 0.0 ohms to the dot left (J923) and 0.0 oms to the dot on the right.

The red dot on the right is connected to pin 6 on IC901, the lower/middle dot (R912) is also connected and the dot at C911 is NOT connected.

Hold that thought. We're hosting a pool party that starts in 30 minutes. I probably won't get back to this for a few hours.

Bill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Moody is correct. That sort of thing is common. One possibility is it was to accommodate a different version of the supply, or to use a different SMPS controller.

Darn!!! C'est la vie. But I'm not going to let you off that easy.

I've marked three points with blue dots. Starting with IC905, pin 3, what are the resistances to the other two points?

I've marked three points with red dots. Are any of them connected to IC901, pin 6?

And I've marked 6 semiconductors with yellow circles. Check these for shorts. What are the marking codes on the two transistors?

PlainBill

Pool party is up my alley, I went to state in swimming. I swam the 500yd, 200yd and 100 yard almost 30 years ago. I wish I was in that kind of shape.

One thing I do need to ask is how do I test the semiconductors for shorts?
I've tested the resistance across the leads to find no conductivity.
Aslo the markings on the two black transistors are 36 5J (the 36 is on the horizontal and the 5J is written vertical. That may or may not be improtant).

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Well, this is how one is to learn, respectfully from guys like you. So I've tested the IC905 to the blue dots: 0.0 ohms to the dot left (J923) and 0.0 oms to the dot on the right.

OK, that works. The Emitter of the phototransistor is tied to ground.

The red dot on the right is connected to pin 6 on IC901, the lower/middle dot (R912) is also connected and the dot at C911 is NOT connected.

OK, that works too. To confirm the interconnections, verify all red dots are connected; all blue dots are connected, and all pink dots are connected.

I'm unable to come up with any data on the transistors.

I use a two step process for testing semiconductors. It uses a DMM with a very low voltage to measure resistance - low enough the junction is never forward biased.

For any diode, set the DMM to the 200 ohms range. The diode should appear open in either direction. Now switch to the diode test range. In one direction the DMM will indicate 'Open', reverse the leads and it will show about .5 Volts.

For a transistor, I think of the package as a little alien with his tiny head on top, a very wide body, and two feet. With the DMM set to the 200 ohms scale, measure the resistance from the left 'leg' to the 'head', from the left leg to the right leg, and finally from the head to the right leg. It should read open in all cases. Now set the meter to the diode test range, and test between each combination of the three legs.

PlainBill

[Dgtech]

Re: Philips 32PFL3403d/27 LCD NO POWER

The only reason why I linked the two together (philips and LG) is because of lots of documentation proudly show some type of marriage between the two. I may be wrong. (see letterhead)

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

The only reason why I linked the two together (philips and LG) is because of lots of documentation proudly show some type of marriage between the two. I may be wrong. (see letterhead)

I'm not going to research this, but as I recall one of the references in my earlier post indicated LG Electronics owns a large part (40%?) of LG Display. I think you have found who owns another large part of LG Display. And given the problems with the LG master-slave inverter, I won't claim they are a top of the line electronics manufacturer.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

OK, that works. The Emitter of the phototransistor is tied to ground.


OK, that works too. To confirm the interconnections, verify all red dots are connected; all blue dots are connected, and all pink dots are connected.

I'm unable to come up with any data on the transistors.

I use a two step process for testing semiconductors. It uses a DMM with a very low voltage to measure resistance - low enough the junction is never forward biased.

For any diode, set the DMM to the 200 ohms range. The diode should appear open in either direction. Now switch to the diode test range. In one direction the DMM will indicate 'Open', reverse the leads and it will show about .5 Volts.

For a transistor, I think of the package as a little alien with his tiny head on top, a very wide body, and two feet. With the DMM set to the 200 ohms scale, measure the resistance from the left 'leg' to the 'head', from the left leg to the right leg, and finally from the head to the right leg. It should read open in all cases. Now set the meter to the diode test range, and test between each combination of the three legs.

PlainBill

All the semicinductors tested open with the DMM set at the 200 range. Now with the dmm set to the diode test, ZD902 tested open in one direction, .5v reversed; D913 tested open/.624v reversed; ZD907 open/.71v; ZD901 open/.71v. The transistor Q906 tested open left leg to head, 0.7v one way between legs and .71 one way between the right leg and head. The transistor q905 tested open left leg to head, .722v one way leg to leg and 1.45v right leg to head one way.

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

All the semicinductors tested open with the DMM set at the 200 range. Now with the dmm set to the diode test, ZD902 tested open in one direction, .5v reversed; D913 tested open/.624v reversed; ZD907 open/.71v; ZD901 open/.71v. The transistor Q906 tested open left leg to head, 0.7v one way between legs and .71 one way between the right leg and head. The transistor q905 tested open left leg to head, .722v one way leg to leg and 1.45v right leg to head one way.

That looks like Q905 is bad. To summarize, we are looking for a SOT-23 transistor with marking codes 36 5J. Neither show up in the references I have.

I've got a handle on how to tackle this; I suspect this is an NPN small signal transistor. I'm going to have to verify this. Tomorrow.

PlainBill

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Man, I'm exercising brain cells that have been dormant far too long. At one time I could pull this off the top of my head; now I had to dig for it. C'est la vie.

I've marked up Q905 and Q906. Set the DMM to the diode test range and place the RED probe on the B (base) of Q906. Note the readings when you place the black probe on the E (emitter) and C (collector) pins; they should be roughly 0.5 to 0.7 volts. Do the same with Q905. The readings should be close, and these are NPN transistors.

If it shows open in all cases, place the BLACK probe on the base and use the red probe to check emitter and collector. 0.5 to 0.7 volt readings indicate they are PNP transistors.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Man, I'm exercising brain cells that have been dormant far too long. At one time I could pull this off the top of my head; now I had to dig for it. C'est la vie.

I've marked up Q905 and Q906. Set the DMM to the diode test range and place the RED probe on the B (base) of Q906. Note the readings when you place the black probe on the E (emitter) and C (collector) pins; they should be roughly 0.5 to 0.7 volts. Do the same with Q905. The readings should be close, and these are NPN transistors.

If it shows open in all cases, place the BLACK probe on the base and use the red probe to check emitter and collector. 0.5 to 0.7 volt readings indicate they are PNP transistors.

PlainBill

well now,... on Q905, with the rod probe on "B", open all cases, so with the black probe on "B" I get .724 from B to E and .719 from B to C. (if I switched the legs, the right to C(red) I get the 1.45 as before, FYI)

For 906, I treated the left leg as E, right as B and C as the head: from B to C(red) I get .7 to both E&C, (if I switchd legs made the left leg B and the right E, I get B-C=1.87 and B-E open)

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

Huh????

You have thoroughly confused me. Note the attached picture of a SO-23 package. This is the standard pinout for BJT transistors. If these are BJT transistors and your DMM makes the red lead positive for the diode test, you should get the following results IF you are testing a transistor out of circuit.

For an NPN transistor:
Red lead to B, black lead to E .7 V
Red lead to B, black lead to C .7 V
All others should read open.

For a PNP transistor:
Black lead to B, red lead to E .7 V
Black lead to B, red lead to C .7 V
All others should read open.

In circuit some readings (particularly the 'open' combinations) will be different.

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

Huh????

You have thoroughly confused me. Note the attached picture of a SO-23 package. This is the standard pinout for BJT transistors. If these are BJT transistors and your DMM makes the red lead positive for the diode test, you should get the following results IF you are testing a transistor out of circuit.

For an NPN transistor:
Red lead to B, black lead to E .7 V
Red lead to B, black lead to C .7 V
All others should read open.

For a PNP transistor:
Black lead to B, red lead to E .7 V
Black lead to B, red lead to C .7 V
All others should read open.

In circuit some readings (particularly the 'open' combinations) will be different.

PlainBill

ok, for both Q905 and Q906 I get:
Black lead to B, red lead to E 0.7 V
Black lead to B, red lead to C 0.7 V

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

ok, for both Q905 and Q906 I get:
Black lead to B, red lead to E 0.7 V
Black lead to B, red lead to C 0.7 V

Good news, bad news. Both are good PNP transistors.

I'm going to take a break from this for a day or so, then review the thread. I'm getting confused by multiple power supplies and am having problems remembering which is which.

Two areas I want to investigate:

1. Some work-alike ICs from different vendors have different operating characteristics. Maybe I've been using the wrong datasheet.

2. Perhaps the problem is not the circuit which turns the supply to the SMPS controller on and off, but the actual voltage it is controlling.

PlainBill

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

I've checked some of my initial assumptions, and found them reasonable. I've made some assumptions from them, and those may not be so reasonable.

First of all, I've labeled the negative lead of the large cap as 'Live Gnd'. To the right of that is a point that seems to be connected to 'Live Gnd' by J923. Please verify.

Next, power for the main SMPS controller seems to come through R947. I've labeled one end as Main SMPS Vcc, and the other as Standby SMPS Vcc?

What is the voltage at the point labeled 'Main SMPS Vcc' and at the point labeled 'Standby SMPS Vcc' without the 3V supply connected? What are the voltages at each of those points with the 3V supply connected to PS_ON. And lastly, what are the voltages across the large cap in with and without the 3V supply?

PlainBill

[Mach1]

Re: Philips 32PFL3403d/27 LCD NO POWER

I've checked some of my initial assumptions, and found them reasonable. I've made some assumptions from them, and those may not be so reasonable.

First of all, I've labeled the negative lead of the large cap as 'Live Gnd'. To the right of that is a point that seems to be connected to 'Live Gnd' by J923. Please verify.YES it is connected.

Next, power for the main SMPS controller seems to come through R947. I've labeled one end as Main SMPS Vcc, and the other as Standby SMPS Vcc?

What is the voltage at the point labeled 'Main SMPS Vcc' and at the point labeled 'Standby SMPS Vcc' without the 3V supply connected? What are the voltages at each of those points with the 3V supply connected to PS_ON. And lastly, what are the voltages across the large cap in with and without the 3V supply?

PlainBill

I have some novice questions:
For the SMPS controller, do I connect the 3V power supply through pin 10 and 6 as before?

When measuring the voltages, should I use the live ground piont as the negative (black probe) and the points 'Main SMPS Vcc' (red) and 'Standby SMPS Vcc' (red)?

Then I assume that when you say PS_ON, I hit the power on button like before?

Mach1

[PlainBill]

Re: Philips 32PFL3403d/27 LCD NO POWER

I have some novice questions:
For the SMPS controller, do I connect the 3V power supply through pin 10 and 6 as before?

When measuring the voltages, should I use the live ground piont as the negative (black probe) and the points 'Main SMPS Vcc' (red) and 'Standby SMPS Vcc' (red)?

Then I assume that when you say PS_ON, I hit the power on button like before?

Mach1

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).

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 cap, to the point 'Standby SMPS Vcc?', and to the point 'Main SMPS Vcc?'

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.

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