Philips 37PF7321/98 cannot turn on

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

What is happening???

I jump a ground to Gate and now the Gate is 20v and Yellow S(source) is 5v.

And the pin 3 of 1305 is 0v.

When I power off and on the tv, the led light on the front panel is green and stay green. Before this, the led is green and after about 2 sec will turn red.

Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

How is this possible?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

How is this possible?

What is happening???

I jump a ground to Gate and now the Gate is 20v and Yellow S(source) is 5v.

And the pin 3 of 1305 is 0v.

When I power off and on the tv, the led light on the front panel is green and stay green. Before this, the led is green and after about 2 sec will turn red.

This is driving me nuts!

Now when I power up the tv, the front panel LED light is off. I press the power button and the LED turned green. The tv screen also lighted up! I swear I didn't do anything.

Am I seeing things? I better go and sleep.

[selldoor]

Re: Philips 37PF7321/98 cannot turn on

Great stuff - hope it lasts - I dont know if its possible to unstick a stuck transistor- maybe?

If it doesnt come on again try heating that section of the board with a hairdryer maybe
getting some voltage through heated something up making it work.

[budm]

Re: Philips 37PF7321/98 cannot turn on

Darn, 143 posts and the TV start functioning by itself.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

looks like we found part of the issue
now if you do that with the 3 pin wire connected to the power supply, the relay might just kick on

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

Just to be sure, I have remove the ground to G. And the voltage of the Gate is still 20v and the Source is still 5v.

How is this possible?

you charged the transistor and it activated . I THINK !

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

Darn, 143 posts and the TV start functioning by itself.

IT IS SAYING, Stop poking me !!

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Great stuff - hope it lasts - I dont know if its possible to unstick a stuck transistor- maybe?

If it doesnt come on again try heating that section of the board with a hairdryer maybe
getting some voltage through heated something up making it work.

I just check with the 3 pin plug 1305 connected. The Gate is 20v and the Source is 5v. Pin 1 and 2 of 1305 are 5v. Pin 3 is 0v.

When I power up the TV, no front panel LED light. Press the power on button and the LED light turn green and stay green. Screen on TV also lighted up.

[stj]

Re: Philips 37PF7321/98 cannot turn on

you charged the transistor and it activated . I THINK !

more likely it has a slight leak and is feeding back into the gate./base

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Now the TV screen is not lighted. Voltages at mosfet 7531 and 3 pin plug 1305 no change.

TV is unstable.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

so that 20-20 and 5 are still at the transistor even when you power it off with the power button ?
To me that 20volts does not sound right
Also do you hear the relay click off when powering it off ?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

so that 20-20 and 5 are still at the transistor even when you power it off with the power button ?
To me that 20volts does not sound right
Also do you hear the relay click off when powering it off ?

When I first turn on the main without pressing the power on button, there is 20v and 5v and Gate and Source respectively but no green LED light on front panel.

When I press the power on button, green LED turn on. 20v and 5v still on.

Did not hear the relay click when pressing the power on button on and off. Only hear relay click when turn off main power.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

unplug the 11 pin wire on the standby board, then remove the number 7 wire from the plug
(you have to slightly lift the clip on the side of the plug with a pointy object and pull the wire out)
then power up
now check the voltages on the board that we were checking at the transistor and 1305
and do a separate check on the wire and the pin that we just removed

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

unplug the 11 pin wire on the standby board, then remove the number 7 wire from the plug
(you have to slightly lift the clip on the side of the plug with a pointy object and pull the wire out)
then power up
now check the voltages on the board that we were checking at the transistor and 1305
and do a separate check on the wire and the pin that we just removed

When pin 7 removed, 20v and 5v still there. 1305 Pin 1 and 2 are 5v. Pin 3 is 0v.

11 pin wire:
Pin 4 is 12v
Pin 5 is 5v
Pin 7 is 5v
Pin 9 is 12v
Others are 0v

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Even with main power off, the Gate of 7531 still has voltage, 14v and discharging slowly.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

ok
with all power off and with it sit to discharge a bit
check resistance in both directions from the Drain (yellowD) to the Gate pin (Yellow G)
if zero or close to it, the transistor went bad

going to need to cut a trace to isolate the Gate pin on that mosfet
use an exacto knife or the like and cut out the yellow section at the end of the pink arrow
I am trying to see if the gate is causing the 20 volts or the board itself
Picture attached if I remember this time

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

ok
with all power off and with it sit to discharge a bit
check resistance in both directions from the Drain (yellowD) to the Gate pin (Yellow G)
if zero or close to it, the transistor went bad

going to need to cut a trace to isolate the Gate pin on that mosfet
use an exacto knife or the like and cut out the yellow section at the end of the pink arrow
I am trying to see if the gate is causing the 20 volts or the board itself
Picture attached if I remember this time

Resistance from Drain to Gate is OL both direction.

7531 is new. Is it really necessary to cut trace? I have never done this.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

7531 is new ???
when did this get changed ???

yes, you have to cut it since there are no jumpers to remove.
it's an easy redo

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

7531 is new ???
when did this get changed ???

yes, you have to cut it since there are no jumpers to remove.
it's an easy redo

It was replaced yesterday before our test. I replaced it because I wanted to test it out of circuit and since it is out, I replaced a new one.

Ok, trace is cut.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

now recheck usual voltages at G D S and at 1305 and also check the pad to the right of the cut