Vizio M550SV No Power/Lightning Strike

[gideon277]

Re: Vizio M550SV No Power/Lightning Strike

With mainboard disconnected I get 82vDC on each leg with mainboard disconnected for a total of 164vDC.

[keeney123]

Re: Vizio M550SV No Power/Lightning Strike

My experience with lighting strikes is it takes out most IC including regulators. Of course this was a long time ago when I repaired Nielsen rating electronics. That was TTL circuitry Op Amps, Multiplexer A to D converters. Lighting would virtually take out everything and if I did not replace everything then somewhere down the line the unit would make a return trip.

[gideon277]

Re: Vizio M550SV No Power/Lightning Strike

Yes but I would hate to jus throw two new boards in this tv

[keeney123]

Re: Vizio M550SV No Power/Lightning Strike

It may not just of stop there it might also have taken out the electronics that are built into the screen.

[gideon277]

Re: Vizio M550SV No Power/Lightning Strike

Well I am at a loss because I do not know if each cap is supposed to individually have 160vDC or if two caps combined are supposed to have 160vDC.

[keeney123]

Re: Vizio M550SV No Power/Lightning Strike

Well I am at a loss because I do not know if each cap is supposed to individually have 160vDC or if two caps combined are supposed to have 160vDC.

I do not know the circuit, but I would say if the caps are in parallel you have 160V on each cap and if in series than the two caps together would give you this. That can be check with an ohm meter. If the two + on the caps are connected together and the two - of the caps are connected together than that is parallel. If one - of one cap is connected to ground and the same caps + is connected to the - of the other cap that would be in series. Otherwise maybe Bud M will explain what he want measured.

[gideon277]

Re: Vizio M550SV No Power/Lightning Strike

Screw it its going in the dumpster.

[MagicSmoke]

Re: Vizio M550SV No Power/Lightning Strike

Don't throw it yet, 164v across caps is correct when tv is in Stby.

If you have 5v Stby on connector, Then unplug connection to mainboard and use a 1k ohm resistor or a wire to jumper from 5v Stby to Power-on pin. Volts across caps should then rise to >390volts.

Then check at connector for 12 volts if all is correct then it's a mainboard problem usually.

You can also use another resistor or wire from 5v Stby to BL-on while power on jumper is still attached to see if B/lights will come on.

If all this works properly then main is bad for sure.

[keeney123]

Re: Vizio M550SV No Power/Lightning Strike

After reading the whole post I would say you did not have a direct hit by lightening. A direct hit does not allow time for the safety systems to protect the power supply board. This does not seem to be your case so this TV maybe worth figuring out what is wrong with it. Seems like MagicSmoke will help you through this.

[Alex-g]

Re: Vizio M550SV No Power/Lightning Strike

You say you did a thorough visual exam. Does this include the rear of the boards?

There may be smokey bits / burned tracks on the rear of one of them.


Those caps are 450v rated, feels strange they would be in series and not parallel for filtering the dc...

Also those black discs should be Polythermal cutouts, they're *designed* to reset after a surge, but they can fail. They should read very low resistance like a fuse, otherwise one could be faulty.

Theres a chip directly above the word COLD on the right hand side, can you confirm the legs look ok on that? It may just be the shadow but it looks a little funny

[keeney123]

Re: Vizio M550SV No Power/Lightning Strike

I do not think they are in series. The way people are asking gideon277 is confusing. They are saying the legs of the two caps. What I think they mean to say is one cap has two legs and when one measures that voltage it is suppose to be 164 VDC and if you measure the voltage of the other 68 uF cap on it's two legs one will get 164 VDC. Instead they have combine both caps as the legs of the two caps. Confusing. So actually the caps have a total of four legs not two legs of two caps. Just that they may be tied together. Instead they needed to say the two nodes of the two caps.

[budm]

Re: Vizio M550SV No Power/Lightning Strike

One way to find out for sure is for us to see good clear pictures of the bottom side of the board or if the negative leg of each main filter caps are tied together, same for the positive leg of both caps.
I do not believe they are connected in series because the caps are rated at 68uF, so the total capacitance of the two caps in series will be only 34uF. This power supply board also has PFC Voltage booster so the output of the PFC will be close to 400VDC so 450VDC caps rating are used in the circuit.

[ecking767]

Re: Vizio M550SV No Power/Lightning Strike

Screw it its going in the dumpster.

if you live in south Florida I will take off you hand