when i turn on, Philliips TV is not on

[R_J]

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

You can't check the ic with a meter.

[Nish]

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

I test with continuity test The IC901

Pin 8 is gnd So black probe on it and touch pin3 , it has beep. Also once I plug the board outlet and unplug check pin5 has beep for few min then stop.

[Nish]

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

I don't know what else to check, without a scope to see what the ic is doing. The ic should be pulsing the (internal mosfet) drain, that should be pulsing the primary and there should be some voltage on the secondary, if there is nothing at all I can only guess that the ic is defective.

Thanks for helping me R_J. I will check if I have new IC and if I have I will replace and update you.

[R_J]

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

I don't know what else to check, without a scope to see what the ic is doing. The ic should be pulsing the (internal mosfet) drain, that should be pulsing the primary and there should be some voltage on the secondary, if there is nothing at all I can only guess that the ic is defective.

[Nish]

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

C9050/951 would only cause a problem if they both were shorted.
As a test. Monitor for voltage across C951a and with the power supply pluged in, temporarly short PC901 pins 3 to 4 and see if you get any voltage across C951a

Still 0v

[R_J]

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

C9050/951 would only cause a problem if they both were shorted.
As a test. Monitor for voltage across C951a and with the power supply pluged in, temporarly short PC901 pins 3 to 4 and see if you get any voltage across C951a

[Nish]

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

D950 and D951 are schottky diodes, they have a lower farward voltage drop so .206 is ok.

Oh ok. Do you think the caps (C950 and C951)on that line give trouble? They are no polarity, how can I test in circuit?

[R_J]

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

D950 and D951 are schottky diodes, they have a lower forward voltage drop so .206 is ok.

[Nish]

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

ZD951 seems low in diode mode, I would think it should be around .6xx
If the main board is not connected, you should be safe leaving ZD951 (6.2v zener) out of circuit for now and see if your 5volts comes up

I removed ZD951 and test on diode mode, it reads 0.638. Now I have -0.030.

I measured D950 and D952 are reading 0.206 at diode mode. I am testing on my bench now

[R_J]

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

ZD951 seems low in diode mode, I would think it should be around .6xx
If the main board is not connected, you should be safe leaving ZD951 (6.2v zener) out of circuit for now and see if your 5volts comes up

[Nish]

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

Lift one end of D903, this will eliminate any problems caused by ic902 circuit. Then make sure ZD951 is not shorted.

I lift the one end of D903 Still same. No 5v. ZD951 = 0.213 in diode mode.

[R_J]

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

Lift one end of D903, this will eliminate any problems caused by ic902 circuit. Then make sure ZD951 is not shorted.

[Nish]

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

Time to start over and work on the power supply out of the tv and get a stable standby AL+5V. Like I said many times, NOTHING works without a stable standby voltage as it not only supplies the main board it also provides the VCC for the rest of the power supply. And REMEMBER, the standby AL+5V uses CN2 pin 11 (or C951A) for output ground.

The (5v) that you measured across ZD907 is provided internally by the ic. Ther will also be a vcc voltage provided by the ic. This vcc voltage is a small current and slowly charges C912. The ic will only charge C912 to around 6~8 volts. The ic will start to PULSE the drain pin and this will PULSE the transformer primary. When this pulsing happens, a voltage is induced in the secondaries of the transformer. This is where D906 comes into play. D906 charges C912 to ABOVE 12 volts to tell the ic to come out of standby and produce PULSES of longer duration.
Once C912 has more than 12 volts (17 volts). you will also have voltage on the secondary C951A. This should be around 5 volts. This secondary 5 volts feeds down to PC901 pin1 and also IC951 (this is a reference regulator) This regulator controls the voltage on pin2 of PC901. When this circuit is working properly, it provides FEEDBACK causing the voltage across ZD907 to drop and regulate the circuit voltage.

Thanks R_J. These are the voltage around the IC901

[nomoresonys]

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

Looks like r j has it step by step in post #67, see if C912 comes up to proper voltage.

[Nish]

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

Simple test, unhook all connectors from powerboard, with just ac plugged in to powerboard, do you have standby voltage??

No I don't have it.

[R_J]

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

Time to start over and work on the power supply out of the tv and get a stable standby AL+5V. Like I said many times, NOTHING works without a stable standby voltage as it not only supplies the main board it also provides the VCC for the rest of the power supply. And REMEMBER, the standby AL+5V uses CN2 pin 11 (or C951A) for output ground.

The (5v) that you measured across ZD907 is provided internally by the ic. Ther will also be a vcc voltage provided by the ic. This vcc voltage is a small current and slowly charges C912. The ic will only charge C912 to around 6~8 volts. The ic will start to PULSE the drain pin and this will PULSE the transformer primary. When this pulsing happens, a voltage is induced in the secondaries of the transformer. This is where D906 comes into play. D906 charges C912 to ABOVE 12 volts to tell the ic to come out of standby and produce PULSES of longer duration.
Once C912 has more than 12 volts (17 volts). you will also have voltage on the secondary C951A. This should be around 5 volts. This secondary 5 volts feeds down to PC901 pin1 and also IC951 (this is a reference regulator) This regulator controls the voltage on pin2 of PC901. When this circuit is working properly, it provides FEEDBACK causing the voltage across ZD907 to drop and regulate the circuit voltage.

[nomoresonys]

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

Simple test, unhook all connectors from powerboard, with just ac plugged in to powerboard, do you have standby voltage??

[Nish]

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

I did not do anything but now I am reading 1.886v.

[R_J]

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

You must have poor solder connections somewhere because in one post you HAVE 5 volts standby on C915a, The next post you have NO votage, then in another post the voltage is going from .1~5 volts.

[Nish]

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

So you think that just because you have 5 volts on ZD907 you should have 5 volts for to supply the main board? Have another look at the schematic.
in post #50 you said:
Where is this voltage coming from???????

By the way, before I put it in, I had 5v at the C915A. Since you said to put resistor to measure. I want to verify what voltage at there. So I can see after I solder resistor.