Philips 40PFH6510/88 not powering on

[ph445]

Hello,

I have a Philips 40PFH6510/88 TV which is not switching on. No no standby led, no nothing. There was no bang, no smoke, it was simply switched off and next day it did not switch on.

I got the power PCB out and visually checked it, I did not see anything unusal on it, the fuse is OK and no cracked, burned components on either side, capacitors looks OK to me.

Both big 450V capacitors are charging up to around 330V but on the secondary side I can't get any reasonal voltage on any output pins. Most are around 0.2-0.3 V. (not sure which one is standby, but I think standby should be above this level)

I checked all 3 optocouplers, not shorted. I checked all diodes I thought to be a diode, all good.

I replaced 1 FET (K22A10N1) I thought was not OK, but nothing changed. (probably was a waste of time it was good)

I checked what is happening on the transformers' primary side on oscilloscope: nothing, except every 10-12 seconds there's some AC voltage for a couple milliseconds and it goes back to nothing.

Service manual: here

Thanks for any ideas, hoping to learn from this a lot

[nomoresonys]

Re: Philips 40PFH6510/88 not powering on

You probably checked all the transistors for shorts/low ohms.

[zwarder]

Re: Philips 40PFH6510/88 not powering on

The large surface mount diode on bottom of board could be shorted, I have had that fault with similar philips psu. Your pictures are not clear enough

[Diah]

Re: Philips 40PFH6510/88 not powering on

known issue; at this area.. R- Open or changed Value Fet. caps.

[ph445]

Re: Philips 40PFH6510/88 not powering on

Thanks for all of you for ideas, I will check these and come back.
I'll try to make better pictures.

[ph445]

Re: Philips 40PFH6510/88 not powering on

The large surface mount diode on bottom of board could be shorted, I have had that fault with similar philips psu. Your pictures are not clear enough

Hmm, this looks like shorted.
I order one and get back.

[ph445]

Re: Philips 40PFH6510/88 not powering on

known issue; at this area.. R- Open or changed Value Fet. caps.

Maybe I should not test it in the PCB, but it doesn't look like a fet according to the tester.

It the diode replacement doesn't help I will solder this out and test it again.

[nomoresonys]

Re: Philips 40PFH6510/88 not powering on

Apparently it's a diode, whats the designator beside it, does it start with a D or Q, D for diode, Q for transistor/mosfet. Hard for someone to tell what they are without good sharp focused pictures.

[ph445]

Re: Philips 40PFH6510/88 not powering on

Apparently it's a diode, whats the designator beside it, does it start with a D or Q, D for diode, Q for transistor/mosfet. Hard for someone to tell what they are without good sharp focused pictures.

It's a k11a65d, should be an N channel FET.

It's label on PCB is Q9301

[lotas]

Re: Philips 40PFH6510/88 not powering on

You can also see there that this is a Diode: Schottky rectifier, SMD, 100V, 5A

[ph445]

Re: Philips 40PFH6510/88 not powering on

You can also see there that this is a Diode: Schottky rectifier, SMD, 100V, 5A

Thanks - also for nomoresonys - I already learnt a lot

[ph445]

Re: Philips 40PFH6510/88 not powering on

Look like replacing the 100V diode solved the issue, I see normal voltages on the DC side.

But my soldering sucks. I tried to apply generous amount of solder, but it's skewed.
Should I start again (not lazy but afraid of too much heat to the diode) or is it good enough?

[lotas]

Re: Philips 40PFH6510/88 not powering on

Leave it like that, it will work

[ph445]

Re: Philips 40PFH6510/88 not powering on

Leave it like that, it will work

Thanks.

I'll try it in the TV tomorrow.

[ph445]

Re: Philips 40PFH6510/88 not powering on

Thank you all, the TV is working!

[nomoresonys]

Re: Philips 40PFH6510/88 not powering on

Thank you very much for the followup, there's SOO many rude crude people that don't do it, nice save.