when i turn on, Philliips TV is not on

[R_J]

Re: when i turn on, Philliips TV is not on

IC951= 6.60v I use ground of C951A

I un solder PC901 now I measure that pads. Still same voltage.

I replace PC902 with 817A optocoupler. Still same voltage.

How can I check if C955,C954 are shorted. Can I lift one pad of cap?

Just check C955/954 in circuit.

[Nish]

Re: when i turn on, Philliips TV is not on

What are the voltages on IC951? something is wrong in that circuit, that is why there is no regulation happening. Maybe shorted C955,C954? I guess it might be PC901? if you don't have one try exchanging PC902 with PC901.

IC951= 6.60v I use ground of C951A

I un solder PC901 now I measure that pads. Still same voltage.

I replace PC902 with 817A optocoupler. Still same voltage.

How can I check if C955,C954 are shorted. Can I lift one pad of cap?

[R_J]

Re: when i turn on, Philliips TV is not on

What are the voltages on IC951? something is wrong in that circuit, that is why there is no regulation happening. Maybe shorted C955,C954? I guess it might be PC901? if you don't have one try exchanging PC902 with PC901.

[Nish]

Re: when i turn on, Philliips TV is not on

The shunt regulator should be pulling pc901 pin 2 close to ground, When it is working you should have about 2~3 volts on PC901 pin2 and around 4~5 volts on pin 1. with about 1.5 volt difference across pins 1&2 the led would be lit and pin 4 would be closer to 1~2 volts, controlling the ic901

I replaced new ic951(apl431). But still same voltage
PC901 pin1 = 6.60v
PC901 pin2 = 6.60v (use C951A negative for ground)

[R_J]

Re: when i turn on, Philliips TV is not on

The shunt regulator should be pulling pc901 pin 2 close to ground, When it is working you should have about 2~3 volts on PC901 pin2 and around 4~5 volts on pin 1. with about 1.5 volt difference across pins 1&2 the led would be lit and pin 4 would be closer to 1~2 volts, controlling the ic901

[Nish]

Re: when i turn on, Philliips TV is not on

R_J: I have one AP431,can I use it for test?

[Nish]

Re: when i turn on, Philliips TV is not on

So you have no feedback to control the primary so it is trying to output more than the 5 volts on the secondary, That's why the ZD951 is getting hot. It is trying to clamp the voltage to 6.2 volts and thats why it gets hot.
First check that D950,951 &952 are not bad or leaky (they are likely ok)
Next check R954,R955, if they are ok IC951 could be bad
What is happening is IC951 is NOT regulating and bringing pin 2 of PC901 low. Check that PC901 pins 1&2 are not shorted. If the optocoupler is ok, I suspect the apl431 regulator is bad. If you don't have one, check an old switching power supply, they almost all use them but it might be a to-92 case but it would work to test.

PC901 has the same voltage on both pins so the internal led is not turning on, If the led does not turn on, the photo detector (pins 3 & 4) does not conduct, lowering the voltage across zd907. and regulating ic901

D950 = 0.2 ,951= 0.2 & 952 = is not populate

R954 =10k ,R955 = 2.976k

PC901 : when I do continuity test no beep. I checked diode mode pin 1(+) to pin 2(-) = 0.596 and pin 1(-) to pin 2 (+) = 0.608
Unsolder those two pin and measure diode mode pin 1(+) to pin 2(-) = 0.998 and pin 1(-) to pin 2 (+) = OL

But when I measure on the pad of PC901 pin 1 and 2 same voltage at diode mode.

I do not have apl431 regulator now. Once I get new I will update.

[R_J]

Re: when i turn on, Philliips TV is not on

So you have no feedback to control the primary so it is trying to output more than the 5 volts on the secondary, That's why the ZD951 is getting hot. It is trying to clamp the voltage to 6.2 volts and thats why it gets hot.
First check that D950,951 &952 are not bad or leaky (they are likely ok)
Next check R954,R955, if they are ok IC951 could be bad
What is happening is IC951 is NOT regulating and bringing pin 2 of PC901 low. Check that PC901 pins 1&2 are not shorted. If the optocoupler is ok, I suspect the apl431 regulator is bad. If you don't have one, check an old switching power supply, they almost all use them but it might be a to-92 case but it would work to test.

PC901 has the same voltage on both pins so the internal led is not turning on, If the led does not turn on, the photo detector (pins 3 & 4) does not conduct, lowering the voltage across zd907. and regulating ic901

[Nish]

Re: when i turn on, Philliips TV is not on

It may be doing that because of lack of feedback, Check the voltage across ZD907.
You may also need to check the voltage on pins 1 & 2 of the PC901 (note to use C951A negative for ground)

ZD907 = -4.96v
PC901 pin1 = 6.60v
PC901 pin2 = 6.60v

ZD951 and C951A are gets hot

[R_J]

Re: when i turn on, Philliips TV is not on

It may be doing that because of lack of feedback, Check the voltage across ZD907.
You may also need to check the voltage on pins 1 & 2 of the PC901 (note to use C951A negative for ground)

[Nish]

Re: when i turn on, Philliips TV is not on

I have soldered 20v zener diode. Still C912 and C906 are fluctuating. But I have 6.18v at C951A.

[Nish]

Re: when i turn on, Philliips TV is not on

So this ZD904 zener WAS bad, Check what voltage you have across C912.
Also while you are at it, check the voltage across C906
C951A has ZD951, a 6.2 volt zener across it.

C912 = 11v to 16v fluctuation
C906 = 8v to 21v fluctuation

I will order 20v zener diode

[will62]

Re: when i turn on, Philliips TV is not on

But did they actually install this ic in the board and check that it worked properly? Did anyone confirm that the DNP005 operates at 65khz vs 100khz?

That, I don't know. The one asking about the DNP005, did not come back and say there was a problem. It was a pretty rough translation from Spanish, but understandable. BTW, not recommending that the OP go away from the DNP005, just adding that it may have a max VCC of 25v. As you said, a 20v zener is probably OK.

[R_J]

Re: when i turn on, Philliips TV is not on

On another site, someone was commenting on the high failure rate of the DNP005, and recommended that it be replaced with a ICE3BR0665JZ. That ic has a VCC range of 10.5-25v.

I doubt they fail any more frequent than any other standby pwm, the infineon icexxx fail often as well.

But did they actually install this ic in the board and check that it worked properly? Did anyone confirm that the DNP005 operates at 65khz vs 100khz?
Most of the Infineon icexbrxxx ic's have a max vcc of around 25v thats why I suggested the 20v zener.

[will62]

Re: when i turn on, Philliips TV is not on

On another site, someone was commenting on the high failure rate of the DNP005, and recommended that it be replaced with a ICE3BR0665JZ. That ic has a VCC range of 10.5-25v.

[R_J]

Re: when i turn on, Philliips TV is not on

So this ZD904 zener WAS bad, Check what voltage you have across C912.
Also while you are at it, check the voltage across C906
C951A has ZD951, a 6.2 volt zener across it.

[Nish]

Re: when i turn on, Philliips TV is not on

I can't make it out but there is likely another number before the "G", try looking at different angles to see if you can see anything else.
The number on the schematic UDZSTE-17, SHOULD have the voltage after this number (ie: UDZSTE-1722, 22v zener)
Some of the zeners that I looked at that end in G, like WG are only 10~11 volt which is normally too low a voltage

When I lift the zener diode and I have 6.4v at C951A

[R_J]

Re: when i turn on, Philliips TV is not on

Which one should I buy and try.

Without a number or voltage rating, it is a guess, Too high a voltage and you will exceed the ic's VCC (which we don't know without a datasheet) and without the full number from the diode its a guess. I would try around a 20 volt zener diode.
A lot of the infineon ic's (which this is but likely custom) have a max vcc of 22v

[Nish]

Re: when i turn on, Philliips TV is not on

Which one should I buy and try.

[Nish]

Re: when i turn on, Philliips TV is not on

I can't make it out but there is likely another number before the "G", try looking at different angles to see if you can see anything else.
The number on the schematic UDZSTE-17, SHOULD have the voltage after this number (ie: UDZSTE-1722, 22v zener)
Some of the zeners that I looked at that end in G, like WG are only 10~11 volt which is normally too low a voltage

I think it's broken. I cannot see any other mark on it.