when i turn on, Philliips TV is not on

[yoritomo]

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

Hello, sorry maybe i did not read correctly, but never you say that your power supply is unplugged off the mainboard, is it ? Because it may occurs a short on the 5V line of the motherboard ? Try to power the motherboard free of any connection except the ht line of course, to see if +5V recovers .

[Nish]

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

Hello, sorry maybe i did not read correctly, but never you say that your power supply is unplugged off the mainboard, is it ? Because it may occurs a short on the 5V line of the motherboard ? Try to power the motherboard free of any connection except the ht line of course, to see if +5V recovers .

Power supply is not connected to the main board.

[Nish]

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

Why are you looking at that circuit? you need to fix the standby circuit first. Look at the schematic...there are two resistors across D604 and D603... R617 (51Ω) and R620 (51Ω)

Alright, I will focus on that first

[R_J]

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

The standby circuit needs to be running first because it also supplies the input voltage to IC902 regulator ic, that supplies the VCC to IC601 etc. So you can see without the standby working, the other circuits won't be able to work.
Check the voltage ACROSS C912, that will tell me the state of the ic. The circuit is quite simple, but when you blew up the ic, it may have supplied 160VDC to the other pins, which may have damaged Q904, C905, ZD907, PC901. so make sure none of these parts are shorted.
Hopefully you did'nt get fake replacement ic's

[Nish]

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

IC 901 pin7 =14.91
C915 = 14.91
ZD904 = 14.91
C912 = 14.92
R916 = 14.92
D906 cathode = 14.92
D906 anode and T901 pin 7 = 0
Q904 (G), Q903 (G) and Q902 = 0.1
PC901 pin4 = 2.83
ZD907= 2.83
C905= 2.84
Q904(pin D)= 2.84

[R_J]

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

The feedback pin2 seems to be low, It should be around 5 volts, something on that line could be causing it to be low as the ic should produce the 5 volts internally.
You can also disconnect one side of D903 which will eliminate anything on THAT line causing a problem.

[Nish]

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

Thanks R_J. Finally I got the 5v. ZD907 is the one I replaced. I got 5V on the CN2 pin9 and pin1. How can I get 3v at C906?

[Nish]

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

CN pin12 not pin1...

[R_J]

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

Thanks R_J. Finally I got the 5v. ZD907 is the one I replaced. I got 5V on the CN2 pin9 and pin1. How can I get 3v at C906?

Ok so the standby circuit is now working and you have +5 volts on CN2 pin 9 correct?
But you are missing the Voltage on C906 correct?
You will need more than 3 volts on C906, likely closer to 15 volts. This voltage comes from the standby circuit via D903 and is supplied to the regulator IC902 pin 2. IC902 then supplies the VCC for IC601 and IC801
Note: IC902 needs to be ENabled (pin1) by turning on PC902. This is done by the P-ON-H1 signal.
If you are working with the board on the bench (main board MUST be disconnected from the power supply) you can turn on P-ON-H1 by using a 1kΩ resistor between P-ON-H1 and +5 volts standby [CN2: Pin9-1K-pin12]

[Nish]

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

Ok so the standby circuit is now working and you have +5 volts on CN2 pin 9 correct?
But you are missing the Voltage on C906 correct?
You will need more than 3 volts on C906, likely closer to 15 volts. This voltage comes from the standby circuit via D903 and is supplied to the regulator IC902 pin 2. IC902 then supplies the VCC for IC601 and IC801
Note: IC902 needs to be ENabled (pin1) by turning on PC902. This is done by the P-ON-H1 signal.
If you are working with the board on the bench (main board MUST be disconnected from the power supply) you can turn on P-ON-H1 by using a 1kΩ resistor between P-ON-H1 and +5 volts standby [CN2: Pin9-1K-pin12]

Thanks but before I do this step I measure the connector 2 (CN2). This is the reading I got.

CN2
Pin1 --》4.48
Pin2 --》4.48
Pin3 --》4.48
Pin4 --》4.48
Pin5 --》4.48
Pin6 --》4.48
Pin7 --》4.48
Pin8 --》4.48
Pin9 --》4.48
Pin10 --》0
Pin11 --》0
Pin12 --》4.46
Pin13 --》0
Pin14 --》0

Is this normal?

[R_J]

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

What do YOU think? Pins 5,6,7,8 are GROUND. what are you using for your meter ground? Or you must be counting the pins wrong.

[Nish]

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

What do YOU think? Pins 5,6,7,8 are GROUND. what are you using for your meter ground? Or you must be counting the pins wrong.

I am using the ground of C951A negative lead.

[R_J]

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

The schematic does'nt match the board. That supply seems to be using CN2 pin 11 for ground, and pin 9 is the AL+5v positive.
The +12.5 volts uses pins 1,2,3,4 for positive and pins 5,6,7,8 for ground

[Nish]

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

I found the C120B, C120C shorted. The original capacitor 1000uF 16v 105°C. I have 1000uF 16v 85°C. Can I use it?

[Nish]

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

The schematic does'nt match the board. That supply seems to be using CN2 pin 11 for ground, and pin 9 is the AL+5v positive.
The +12.5 volts uses pins 1,2,3,4 for positive and pins 5,6,7,8 for ground

I do not know which schematic you are talking about. The one I attached match.

[R_J]

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

Then explain how you measure 4.48 volts on all the pins 1~9 (even ground) and yet pin 11 which according to the schematic is also ground, you measured 0 volts?
Have a look at the bottom of the board and trace the grounds. C951 (negative) connects to pin 11, not pins 5,6,7,8

[Nish]

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

Then explain how you measure 4.48 volts on all the pins 1~9 (even ground) and yet pin 11 which according to the schematic is also ground, you measured 0 volts?
Have a look at the bottom of the board and trace the grounds. C951 (negative) connects to pin 11, not pins 5,6,7,8

You have right question? But I am not understand too. Now i do not have 5v at C951A. ZD951 gets hot. I removed then C951A is get hot and C120B get hot. PC902 pin 1 and 2 are read 0.378V in the diode mode.

[R_J]

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

Measure the voltage ACROSS C951A, If C951A and ZD951 (6.2v zener) are getting hot, you must have too high a voltage across them. Where is C120B ? PC902 is used to turn on the main power supply, You chould be checking PC901 which is the feedback for regulation. If the opto is bad or the circuit around it, the primary will not be regulated, that can cause the voltage across C951 to be too high

[Nish]

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

C951A= 5.19v now and still has 5v at pin1,2,3,4 and ground pins. C120B is on the 12v line near the big transformer pin 6, 3, 11,8. After few sec the 5v not there.

I am thinking pson line short.

[R_J]

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

LOOK AT THE BOTTOM OF YOUR BOARD. There is no connection to GROUND for the STANDBY 5.3 volts negative. CN2 PIN 11 is the ground for the the standby voltage NOT PINS 5,6,7,8
CN2 pins 5,6,7,8 are the ground for the 12.5 volts which is on pins 1,2,3,4 To check the 12.5 volts measure ACROSS C120B