Vizio VX37LHDTV10A

[tibimakai]

Re: Vizio VX37LHDTV10A

Thank you. The bulbs wont turn on, because the power supply is already messed up. I need to fix it, I can't spend more money on boards.

[cashkennedy]

Re: Vizio VX37LHDTV10A

Although bulb testing looks cool, why are you resorting to this over a multimeter? Are you getting the right voltages, just worried they are dropping when a load is on the power supply?

The reason i ask is cause at least if your using a multimeter you can check if your getting like 2 volts vs 0 volts, both of which wouldnt make the 24v bulb light..., but would change what id consider was possibly broken.

[tibimakai]

Re: Vizio VX37LHDTV10A

Under load you may get different readings.
For example, w/o bulbs I'm getting 13.3v for 12v and 21.4 for 24v.
With load I'm getting for 12v 20.5v and for 24v I'm getting 0v.
By the way how it's possible to get much higher output then the nominal?

[cashkennedy]

Re: Vizio VX37LHDTV10A

I dont know if this applies to tv power supplys, but in old computer power supplies voltages would be linked so that if you pulled too many amps on 1 voltage it would ruin the other because it had to increase both somewhat.

In computer power supplies its called crossload, and used to be a bigger issue, like if you tried to run to many hard drives relative to what the rest of the parts were using.

So perhaps the 24v rail is being so drained by that bulb, it is trying to drastically raise both the 24v and the 12v at the same time, and so the 12v rises to 20v....

[budm]

Re: Vizio VX37LHDTV10A

Please do not forget from what tibimakai had said, the 24V ground return is not connected to other Power supply grounds, so there will be no current flow through the 24v lamps setup.

[tibimakai]

Re: Vizio VX37LHDTV10A

usually when there are output issues, the parts that go out are in the secondary or the primary side?

[budm]

Re: Vizio VX37LHDTV10A

So where are you at at this point? No 12v, no 24v when PS_ON is applied, and no loads connected this time?

[tibimakai]

Re: Vizio VX37LHDTV10A

I didn't have time to do much, because I had to look at two other TVs and I have a three years old.
I'm trying to figure out which power supply to work on, I have three, one partially taken apart.
The original one has voltages, but there are all over the place, the "new" one has only the standby voltage, Vizio logo turns white and in like five seconds back to orange.
I have the 46" Samsung which works, I will replace the caps on it just to be sure, so this one has priority. The 37" Toshiba also works, but has the pop, this should have priority also. I have a 42" Sharp which is again a bigger better TV(read more money making), should have more priority, but this little Vizio PS is bugging me, I can't let it go.
By the way, a power outage what can do to a TV? The Sharp's case.

[budm]

Re: Vizio VX37LHDTV10A

OK, not sure if we already try this with the new power supply since the thread is getting long and hard to keep tracks of what was done or no done. Since the LOGO did turn white and then it goes orange, it can be that it goes into safety shutdown, Disconnect both power cables to both inverter boards and see if the logo will stay white.

[tibimakai]

Re: Vizio VX37LHDTV10A

I did that. Every time I try a new PS I do that, I connect just the main board and the T-con.
Something burned out on the PS because I have smelt it.
OK so "we" will be working on the new one.
Now I have to go to pick up another 40" Sony 40V4150, looks like it's completely dead. Maybe a fuse?
There is another one with a 1/4 of screen is black vertically(40S4100), I'm afraid of this, maybe bad panel.
Tomorrow I will measure the PS and I will post it here what I'm getting.

[budm]

Re: Vizio VX37LHDTV10A

" I connect just the main board and the T-con.
Something burned out on the PS because I have smelt it." now that does not make sense since there is no load for the 24v but there is load for the 12v, the 12v and 24 v are generated by the same transformer (two windings, one for the 12v and one for the 24v) and drive circuits, which means you should have 24vdc with no load connected to the 24v.

[tibimakai]

Re: Vizio VX37LHDTV10A

That is what I did initially, then I disconnected everything and used the bulb tester and the benchtop PS for the 3.3V. Then I blew the PS.

[tibimakai]

Re: Vizio VX37LHDTV10A

So I did some measurements, no output voltage, only the 5v.
I have checked the big cap and I'm getting an initial spike and then drops to 169v. So basically here is a problem.

[tibimakai]

Re: Vizio VX37LHDTV10A

so, which parts are responsible for the high voltage on the big cap?

[budm]

Re: Vizio VX37LHDTV10A

It sounds like the PFC Voltage booster circuits is not working, the voltage on that cap should go up to 390~400Vdc when PS_ON is applied.

[tibimakai]

Re: Vizio VX37LHDTV10A

Thank you.
So next step is to look up the data sheet for the little IC which controls the PFC?

[budm]

Re: Vizio VX37LHDTV10A

Yes, By the, any of the boards you have has working PFC section?, if it does, then it may be easier to troubleshoot the 12v24v dc section instead.

[tibimakai]

Re: Vizio VX37LHDTV10A

Yes the other one has a good PFC, just the secondary voltages are all over the place.
So we should go with that then? That is the original one. To me it seems the better choice since it has some voltages at every output.

[budm]

Re: Vizio VX37LHDTV10A

Yes, get the P/N of that SMPS IC for the 12/24V and check the VCC pin.

[tibimakai]

Re: Vizio VX37LHDTV10A

I will do that tomorrow, it's to late now.
The multimeter's black wire goes to the big cap's negative? By the way on some of the Fet transistors still shows khz.