32PFL3606 Fuse blow invert mosfet shorted

[rpater]

Problem with Philips LCD, fuse is out and one of the inverter mosfets is shorted.

Is this a case of poor power supply design allowing the fet to fail do to use of the lcd or is more that I have to check?

Type fet this http://pdf1.alldatasheet.com/datashe...D...F8N60.html

[budm]

Re: 32PFL3606 Fuse blow invert mosfet shorted

The board looks a little brown under the inverter transformer, should remove and inspect the transformer, this can be due to worn out lamps or just worn out or under rated transformer.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Mosfets are replaced and fuse is ok now, only the back-lights will not lights up.

There is no 12v and 24v is come on and dropping to 0v, S/B is make just one swing to 3,3v. 5v standby is steady, ENA pin is also makes just one swing to 3,3v and the bake to 0v. So i think the PSU is turned in a protection.

I have removed the UBA ic no luck all is stay the same, also look for short on the main-pcb and disconnected the 12v and 24v no luck also. So I running out of option, maybe there is some one that can give me the golden tip.

[CapLeaker]

Re: 32PFL3606 Fuse blow invert mosfet shorted

If the mosfet blows, usually there is more shorted or bad. Check the gate resistors etc, maybe IC801 is bad.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Gate resistor is replaced for a new one, IC801 is not sorted. Because when i remove IC801 the 12v and 24v are doing just the same.

[CapLeaker]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Does the PFC work? In other words, do you get more than 360v on the main filter cap? Does it come up at all?

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Yes 313V, but on the vcc pin from the FAN6991 is there only 0.3V also on the vcc of the NCP1271D65R2G

[CapLeaker]

Re: 32PFL3606 Fuse blow invert mosfet shorted

So the PFC isn't working then. If the PFC works there should be more than 360V on the 450V filter cap. 300 and some change won't cut it. Also I think Vdd-S is missing or pulled to GND. That is on 3 IC's. See what you get at Q806 and the Zener ZD801. Read the VDD pin on IC801. Check ZD909 and Q903 for piece of mind.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Q806
B = 0.38V
C = 0.38V
E = 0.00V

ZD801
A = 0.00V
C = 0.38V

IC801
VDD PIN = 0.00V

ZD909 Not shorted
A = 0.00V
C = 0.38V

Q903 Not shorted
B = 9.86V
C = 0.38V
E = 9.86V

Maybe you have so more information, thanks a lot for your support.

[budm]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Can I get the list of the pin names of that white connector of that power supply/inverter board?
It sounds to me the signals from the main were present to turn on the power supply but then go away.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Yes of course you can get them, here you go. But I have enable the supply with 5V to the ENA, and also tested with 5V to the S/B pin. Same low voltages, on the components.

[jetadm123]

Re: 32PFL3606 Fuse blow invert mosfet shorted

So, if you jumper 5V to the ENA pin, the 12V and 24V output stays constant? If yes, then it sounds like the problem is in the mainboard?

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Nope if I jump the ENA the 12v and 24v is not present. And only the above values are present, ant the 5v standby of the supply is steady.

[budm]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Nope if I jump the ENA the 12v and 24v is not present. And only the above values are present, ant the 5v standby of the supply is steady.

OK, per diagram of the connector pin out, the ENA pin is BL-ON (Backlights on) command pin.
The S/B pin is the PS-ON pin. And when you force on you must remove the cable for that command wire going back to the main board first otherwise you can damage the switched transistor on the main board, and always use the resistor for current limiter.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Yes okay I will get to it tomorrow, thanks for the support so far.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

Just some things i have found the IC 801 UBA IC measured 35ohm if the IC is on the board. The strange thing when the IC is of the board the VDD en GND pin are very normal. So there have to be a short circuit behind this IC or is there possibility that the IC is short inside?

And the above voltage are also higher when the IC is removed, only 313v is still there sometimes it is higher but drops then, maybe this is a protections that see that the IC801 is removed. All voltage are a normal 10V on the other IC in the same circuit.

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

A other strange thing is on the feedback lines of IC909 is there also a voltage of 2.0V by a disable supply and by enable supply is there 0.9V.

And IC902 has a voltage of 3,6v on the FB line by a enable supply, I don't kwone of this normal, but the main cap is still 313v so PFC is not working. Can this have to do with the FB lines?

Only when i unplug and plug the maincord the main cap whil give 400v and the drops to 313v.

[budm]

Re: 32PFL3606 Fuse blow invert mosfet shorted

What DC Voltage do you have between the IC902 VCC (PIN 6) and GND (PIN 4) when S/B is forced on?

[rpater]

Re: 32PFL3606 Fuse blow invert mosfet shorted

10v when s/b is foreced on and with the ic801 removed otherwise with ic801 in places is the voltages 0.8V

[budm]

Re: 32PFL3606 Fuse blow invert mosfet shorted

10V is way too low for the ICs to run.
Check the resistance between VCC pin and GND PIN.
Some thing is loading down, it can be the IC, the zener, or bad filter caps.
See the parts I circled.