Vizio XVT553SV no power

[cguzek]

tv does not get power, no standby led or power.

I opened up, first thing i test is continuity F1 on power supply, and its blown, a T5A 250V

I replace with a 5A 250V Ceramic Time Delay Fuse. Still having everything disconnected from this board, I plug in the AC power cord. The fuse blew right away.

[cguzek]

Re: Vizio XVT553SV no power

I unsoldered the bridge rectifier, and it seems to be testing good, also checked the individual diodes around the bridge and larger capacitors.

I unsoldered first set of mosfets, and one seemed to test good, one bad. Ordered two, found exact match at digikey.

[cguzek]

Re: Vizio XVT553SV no power

unsoldered next set of Q's and they tested good as well


mine is 21914 not 60819 like it is in picture at the number above smk1060

[cguzek]

Re: Vizio XVT553SV no power

unsoldered final single Q and it tested good also.

On the chip above K3532 on mine it reads P00R55 not P7NP03 like it is in picture

[cguzek]

Re: Vizio XVT553SV no power

I don't have a diode testing place on multimeter. Looking to get one soon.

Im testing by checking resistance on highest setting 2000k, on what I think are still good Mosfets i'm getting infinite ohms on pins 1 to 2 and 1 to 3.

Between pins 2 and 3 if red lead is on 2, infinite ohms, if black lead is on 2, i start to get numbers.

Looking at the board from top to bottom (ones on the heatsinks) the readings from pin 2 to three with black lead on 2 and red lead on 3 are:

000
317
200
370
360

On the bad Mosfet, all pins were continuous.

[cguzek]

Re: Vizio XVT553SV no power

If anyone has any other ideas on what to test, and what to replace, please let me know. Just hoping the shorted Mosfet that is continuous on all pins is what's causing the fuse to blow as its already ordered. But wondering what else I should test. Thanks.

[cguzek]

Re: Vizio XVT553SV no power

Also need replacement part numbers for SMK1060 and K3532 if anyone knows digikey part number, thanks.

[Dgtech]

Re: Vizio XVT553SV no power

Without having a schematic in front of me, I'd suggest that you check for a dead short. How to do that quickly would be to measure ohms between the fuse, once it's placed back in, to ground (use that screw hole tab on the bottom left side of the first picture). Do this with the power off. Most likely you will get zero ohms showing a dead short. Id then pull off the bridge rectifier and then try to check for that same zero ohms from fuse to ground. If it's there, then the problem is still on the board between the input power connector and the bridge, which is only about a handfull of components. If the short is not there, then that means it's the bridge OR a few components after it on the primary side of the power supply.

You can also check ohms across the three large caps (top left of first picture).

Start there and report back.

[budm]

Re: Vizio XVT553SV no power

The fuse is in the primary side, the screww hole tab is for the chassis Ground which is the secondary side ground ref, not primary circuit ground (that is why you see black hatched line to show the chassis ground and the hot side on the board), the circuit ground ref for the primary circuit is the negative leg of the large filter cap (primary circuit ground is NOT TIED to the chassis), not chassis ground. You should check the resistance between the two ~ on the bridge rectifier to see if it show shorted circuit or not, then do the same ohm reading between + and - pins of the bridge rectifier. You can see blue safety caps that are connected between the chassis ground and the Hot and Neutral on the board.

[cguzek]

Re: Vizio XVT553SV no power

I already have the mosfet K13A60D as shorted, no resistance between any combination of pins, plus all the bridge rectifiers, and mosfets are all unsoldered. So testing them should be easy, with meter in 2000k ohms setting, there are two bridge rectifiers, between plus and minus on bridge i get infinite ohms when red lead on + and black on -, but when reversed i get 572 and 584. Between the middle two pins infinite resistance regardless of lead orientation. That makes the bridges good, correct? I'm not sure.


Also im looking for parts to match other two types of mosfets cuz i figure if one shorted, i might as well replace them all.

[cguzek]

Re: Vizio XVT553SV no power

Well, i have bridge rectifiers still unsoldered. tested between fuse and the ground of the capacitor next to it underneath the board, and there is infinite resistance. So there shouldn't be any shorted components before the bridge?

[budm]

Re: Vizio XVT553SV no power

Souns like it. You can use 75 Watts lamp in place of the fues, if the lamp lights up and stay brightly lit, then you still have shorted circuits. Not sure about the sub for the MOSFET, have to do more searching.
If you are going to lots of repair, you should make one of this box.
http://s807.beta.photobucket.com/use...51060718676068

[cguzek]

Re: Vizio XVT553SV no power

Thanks Budm, appreciate the help, just made a dim bulb tester last night to use in the future. ok, if i cant find replacements i'll order same ones from company other than digikey.

When using dim bulb tester should i just jump fuse, or have fuse in place?

[budm]

Re: Vizio XVT553SV no power

Fuse is not installed, the current will flow through the lamp to feed the circuits.

[cguzek]

Re: Vizio XVT553SV no power

Damn cant even find smk1060, just seems one went bad since both give different readings between pins 2 and 3 with black lead on pin two and red on pin 3

[cguzek]

Re: Vizio XVT553SV no power

oh, ok, got you on the bulb thing in place if fuse

[cguzek]

Re: Vizio XVT553SV no power

Ok, received the K13A60D today, and put it in. There is no longer a short to ground. Have fuse in and its not blowing.

Secondary problem. I only have voltage on the Hot side of the board. The cold side, where all the wires from other boards go in, have no power at all. its like voltage reaches the line in board and stops.

Does anyone know which parts could be causing this, and what I should check?

[cguzek]

Re: Vizio XVT553SV no power

I've included a picture, all points where there is red, these components all have 5.9v or 6v on the primary side, and 0V on secondary side. All other components on primary side have voltage.

[cguzek]

Re: Vizio XVT553SV no power

Well, IM AN IDIOT. I soldered mosfets and whatnot back in, but forgot to resolder in the Bridge Rectifiers. Hope I didn't blow any more components by plugging in without bridge rectifiers in, but my dim bulb tester didn't light any.

Resoldered in the Bridge Rectifier. Now I am getting 5v standby, and the Vizio logo is lit in Orange for standby power. Tried powering on, and got the orange to white light blinking. This lasted a bit. Then once it returned to standby solid orange, I clicked power button and light turned to white, but no picture. There is still just voltage for standby, no other voltages on the pins were on. Dim bulb tester also started to turn on and dimly on and off.

Also noticed buzzing/clicking mixed sound very low coming from either bridge rectifier, or piece circled next to it.

[tom66]

Re: Vizio XVT553SV no power

Forgetting the bridge rectifier is unlikely to cause damage.
Test it without the bulb as the bulb does offer significant power limiting.