Fluid 55 LED 8018758a no backlight

[microvibe]

This tv has same boards as Westinghouse dwm55f2y1 I have standby tv even turns on I can see video with flashlight. I have 24v 12v 5v 3.3v for back light on etc. I get 167v across main cap never changes I get no voltage on the led connectors. Removed led panel tested all leds as well.
Looking for info on how test led driver circuit on psu

[dskall]

Re: Fluid 55 LED 8018758a no backlight

What is number on power board. PFC not working.

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Mp5055-4k1a

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

The blue wafer covered with black shrink tube by the main cap shows open . Aren't they supposed to be closed or show resistance until they blow open?

[budm]

Re: Fluid 55 LED 8018758a no backlight

The blue wafer covered with black shrink tube by the main cap shows open . Aren't they supposed to be closed or show resistance until they blow open?

That is MOV, it will blow if the set is exposed to over Voltages or surge.
The DCV between the two legs of the main filter cap should be 380~400VDC when PS-ON signal from the main board is sent to the power supply to turn on the PFC and the rest of the power supply, if the PFC is not working then that section has to be fixed first.

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Only 167v on main cap blon signal is there from main to pay all other voltages too. Just don't know how to or where to start testing the pfc curcuit.should that mov read closed?

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

I googled the mov testing didn't know what was called before thanks budm . So it's good . This power supply isn't that expensive to replace but I'm tired of just replacing since everything else works on this TV except backlight on I'd like to fix this one. I can solder quite well I replace IC chips on cell phone logic boards these components on the TV or much larger. Just don't have the knowledge to figure out the PFC circuit I have repaired other power supplies on plasmas but then I could download a schematic can't find nothing on this TV

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Anyone work on these boards before have a starting point or a common problem in the PFC

[dskall]

Re: Fluid 55 LED 8018758a no backlight

Need numbers off ic's bottom center and clear pictures of that area

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Can't make out numbers here the pics

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Tbis is one
1607b
Pnaq

The other is
L5599d I think

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

It's l6599d

[dskall]

Re: Fluid 55 LED 8018758a no backlight

1607 is your pfc ic. Pin 8 is input voltage and pin 6 is ground. See what dcv you have when power on

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

I'll have to do that test tomorrow. So if I don't get any DC volts on that PIN that comes from a 50 volt cap is that supplied by one of the mosfet?

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Zero volts on pin 8 of that pfc . I traced it back to a small cap no voltage there

[dskall]

Re: Fluid 55 LED 8018758a no backlight

Not sure but there is probably a transistor that gets switched on when you get ps_on signal

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

I can trace the circuit I think but how do u test the transistors on the back surface mount without power or removing.

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Does the input signal come from l6599d ic?

[microvibe]

Re: Fluid 55 LED 8018758a no backlight

Anyone work on this psu before? Same as Westinghouse. Where does input voltage for pfc come from.

[budm]

Re: Fluid 55 LED 8018758a no backlight

https://www.badcaps.net/forum/attach...5&d=1504545462
Did you trace pin 8 of the PFC IC to see where it f goes?
If you did you would have seen the + Voltage from the AUX winding of the STBY power supply feed the Emitter of the switched transistor Q29, the Collector of Q29 feed pin 8 of the IC through R74.
You can solder wires to Emitter and Collector so you can test the Voltage with ref. to the hot side circuit GND.