Philips 42PFL7403D Doesnt turn on

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

I would try removing the RC line pin3 (there are only 3 signals, keypad (pin7), RC (REMOTE IR receiver, and light sensor pin1, not sure about pin 9 for the TACT SWITCH).

But if I remove the RC pin I cant turn on the TV (with remote control),
well I can check of course if the PSU seems to start up.

[selldoor]

Re: Philips 42PFL7403D Doesnt turn on

@Budm - What about that transistor at 7FA2 if that is shorted might it cause this problem
Pic on Post38

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

@Budm - What about that transistor at 7FA2 if that is shorted might it cause this problem
Pic on Post38

I have replaced the whole LED panel control board, so I think
we can exclude any faulty components on that one..

[selldoor]

Re: Philips 42PFL7403D Doesnt turn on

I have replaced the whole LED panel control board, so I think
we can exclude any faulty components on that one..

Its not on the Led panel control board its in the last picture.

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

Its not on the Led panel control board its in the last picture.

Ok sorry.
It's a BC847B .
I should probably desolder it when testing, or what do you say?
I will test it tomorrow.

[selldoor]

Re: Philips 42PFL7403D Doesnt turn on

Ok sorry.
It's a BC847B .
I should probably desolder it when testing, or what do you say?
I will test it tomorrow.

Sorry, I dont know - that is why I was asking Budm if it might be relevant.

[budm]

Re: Philips 42PFL7403D Doesnt turn on

There are 3 transistors, two are for driving the LEDs, if they are shorted, then the LED will just stay on, they do not send any signals back to the CPU, the other transistor is for auto brightness control of some sort that adjust the backlights brightness depends on room light so I do not believe that will cause the TV not to function. You should be able to disconnect the Remote signal line and use the keypads to turn the TV without using the remote.

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

There are 3 transistors, two are for driving the LEDs, if they are shorted, then the LED will just stay on, they do not send any signals back to the CPU, the other transistor is for auto brightness control of some sort that adjust the backlights brightness depends on room light so I do not believe that will cause the TV not to function. You should be able to disconnect the Remote signal line and use the keypads to turn the TV without using the remote.

OK.
No, I cant turn the TV on with the keys on the keyboard, only with RC.
(When TV has started they seem to work anyway, but if holding a button for more than 1 sec the TV turns off).

If key on keyboard is pressed it shuts down the PSU and TV wount start.

[selldoor]

Re: Philips 42PFL7403D Doesnt turn on

@ Budm - not sure we are talking about the same transistor - I mean the one under the 4 pin connector on the main board.

@Pacmyc Are the 9 wires on a flat cable and inserted into the plug in order. Dont want to get them mixed up! if not you will need to label them. The wires and the metal connector can usually be pulled out of the plug- perhaps needs a tag moving with a very small screwdriver or similar. Remove a wire at a time and see what effect it has. Think you suggested that yourself earlier. Do we know what the 4 wire connector does I have assumed it plugs into the socket in this picture?

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

@ Budm - not sure we are talking about the same transistor - I mean the one under the 4 pin connector on the main board.

@Pacmyc Are the 9 wires on a flat cable and inserted into the plug in order. Dont want to get them mixed up! if not you will need to label them. The wires and the metal connector can usually be pulled out of the plug- perhaps needs a tag moving with a very small screwdriver or similar. Remove a wire at a time and see what effect it has. Think you suggested that yourself earlier. Do we know what the 4 wire connector does I have assumed it plugs into the socket in this picture?

Yes it can be pulled out, but not while the connector is connected in the socket. I will try to cut the cables, and I'll be careful to label the cables.

No, that 4-pin socket on the motherboard is not connected to anything.
The other 4-pin socket on the LED Panel Control is connected to the Keyboard.

<Keyboard> ---(4-pin cable)---> <LED Panel Control> ---(9-pin cable)---> <Motherboard>

[selldoor]

Re: Philips 42PFL7403D Doesnt turn on

Yes it can be pulled out, but not while the connector is connected in the socket. I will try to cut the cables, and I'll be careful to label the cables.

Not sure what you mean? I meant unplug the ninepin cable then take the
individual metal socket on the ends of the wire out of the plastic socket.
If its not too hard it will be easier than cutting and re joining

No, that 4-pin socket on the motherboard is not connected to anything.
The other 4-pin socket on the LED Panel Control is connected to the Keyboard.

<Keyboard> ---(4-pin cable)---> <LED Panel Control> ---(9-pin cable)---> <Motherboard>

Dont ask me why, I thought the keyboard and panel were the same!

Out of interest would the keypad 4 wire cable reach the connector on the main board - odd it has the same number?

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

Not sure what you mean? I meant unplug the ninepin cable then take the
individual metal socket on the ends of the wire out of the plastic socket.
If its not too hard it will be easier than cutting and re joining


Dont ask me why, I thought the keyboard and panel were the same!

Out of interest would the keypad 4 wire cable reach the connector on the main board - odd it has the same number?

I did as suggested. It's pin 5 (3V3 stdby) on the 1M20 connector that needs to get disconnected in order to turn on the PSU.

With pin 5 disconnected I connect to mains.
PSU starts fine, white led flashes. TV starts.
Remote control doesnt work without pin 5 but keyboard do work.
I can reconnect pin 5 after the TV has started, and then RC works.

If keyboard button is hold for about 1 sec or more the PSU directly turns off.

Also important to know, the 3V3 voltage output on PSU is pending 3.1-3.2 V when the cable on 1M20 is connected (incl pin 3), but goes to stable 3.4V when it's disconnected.

Yes, I saw that the 4-pin socket on the mainboard has the same label. Probably it's used on other TV sets. I tested connecting my keyboard to this socket instead of the one on LED panel control board, but didn't notice any difference.

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

@Budm - What about that transistor at 7FA2 if that is shorted might it cause this problem
Pic on Post38

I measured the voltage on this transistor.
When TV is shutdown (and PSU is not working) I have a stable
0.65 V on pin B of the transistor (measured to ground on TV-chassis)
Nothing on E and C.

When PSU starts working the voltage on B is pending between 0.30 - 0.60 V.
Still nothing on E and C.

When mains are disconnected i get about 880 ohms from B -> C and B -> E. Nothing else.

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

I ran the TV with the 3V3 stdby line to led panel control disconnected (without reconnecting it after the TV has started).. Something must have happened because I now I cant start the TV at all.
The background light lits up for a second and then TV goes dead. It feels like the PSU cant supply enough current, or that there is a protection state kicking in. Maybe this well help further trouble shooting..

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

*bump* No more ideas what to try?
So TV goes to trash then

[STB]

Re: Philips 42PFL7403D Doesnt turn on

Hi!

Replace capacitor 2170 (100uF) with a 1000uF elko. On my TV set the voltage drop when pressing the power button of +3V3-STANDBY reduces to 200mV which seems to be sufficient. My TV set works well since this mod.

Regards,
STB

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

Hi!

Replace capacitor 2170 (100uF) with a 1000uF elko. On my TV set the voltage drop when pressing the power button of +3V3-STANDBY reduces to 200mV which seems to be sufficient. My TV set works well since this mod.

Regards,
STB

Something strange about this capacitor.
According to service manual "philips_chassis_q529.1e_la_sm.pdf" it first claims that this cap is a 100 uF 25 V (in the drawing). But, in the Spare Parts List the same service manual says 470 uF 6.3 V. Which one should it be? On the board it is a 470 uF 6.3 V.
If you still think that I should replace it, what voltage should it be?

[STB]

Re: Philips 42PFL7403D Doesnt turn on

In my TV was a 470uF 6V3 elko, i think it is worth trying 1000uF. The voltage rating should be at least 6,3V.

Check with the multimeter the voltage drop reduces significantly.

Regards,

STB

[pacmyc]

Re: Philips 42PFL7403D Doesnt turn on

In my TV was a 470uF 6V3 elko, i think it is worth trying 1000uF. The voltage rating should be at least 6,3V.

Check with the multimeter the voltage drop reduces significantly.

Regards,

STB

OK. The only 1000 uF I've got is a 35 V.
Is it allright to replace with this one?

[Mr Bill]

Re: Philips 42PFL7403D Doesnt turn on

It should be ok to test but i would order the correct one if it works.