Vizio VA19L Won't Power On

[sysvr4]

Re: Vizio VA19L Won't Power On

"Ok, remeasuring the 5V and 12V pads " these voltages are in the secondary side, you will need to use the chassis ground as a ref ground point.

Ok, when I do that, I get 0VDC on all of them.

There are two sections to the power supply board, the Primary (hot) and the Secondary (Cold) side which is isolated from the Primary (deadly side where youe have 120VAC applied to the Primary side of the circuits).
You should have this board powered throgh the GFI outlet to protect yourself in case you body makes contact with the primary side.

Thanks again, that's helpful. So negative leg of the cap on the primary, and chassis on secondary. I'll try to remember that

[sysvr4]

Re: Vizio VA19L Won't Power On

See if Q901 is shorted between G-D, G-S, D-S.

I'm getting some weird indications here on two different multimeters... testing for continuity between G-D, I get a very brief tone and flicker from the tester - less than 1 second - then nothing.

No continuity between G-S and D-S...

[budm]

Re: Vizio VA19L Won't Power On

Please take the resistance reading of the 2.2 Ohms resistor and the kickstart voltage at pin 8 of the IC.
What is the P/N printed on that IC?
Great pictures by the way. What did you use for the even lighting?

[sysvr4]

Re: Vizio VA19L Won't Power On

First, I should apologize for the delay... I have been traveling for the holidays and catching up on work. I've finally had a chance to get back to this project, and wanted to update everyone who's been helping on the progress.

One thing I want to note is that a week or so ago, I was able to procure a replacement power board exactly like the one we've been discussing on eBay for a very reasonable price. I figured even if it did not fix the problem, I could use it as a tool to continue learning about how all this works, and I may even be able to make one working board from the two.

What I've discovered is that the new board appears to work, though I haven't yet installed it in the TV. I tested all the voltages at the connector going over to the main board and they appear normal on the new one (you'll recall I had 0V on all of them on the original, broken board).

Probing around between the two, the main difference appears to be around the IC the budm has pointed out...

Please take the resistance reading of the 2.2 Ohms resistor and the kickstart voltage at pin 8 of the IC.
What is the P/N printed on that IC?

The 2.2Ohm resister at R915 had 0VDC.

On both the old board and the new one the voltage is 178VDC at pin 8 of the IC. Here's where it gets interesting though...

IC Pin - Old Board - New Board
1 - 0VDC - 12VDC
2 - 0VDC - 0VDC
3 - 0VDC - 0VDC
4 - 0VDC - 1.5VDC
5 - 0VDC - 0VDC
6 - 0VDC - 0VDC
7 - 0VDC - 0VDC
8 - 178VDC - 178VDC

What I've been trying in vain to figure out is which pin is the input pin for the IC. In other words, do I have a bad IC, or is pin 1 in the input and the IC isn't getting the 12V it needs to work its magic? I suspect the former given the 178V at pin 8, but I think it's clear at this point what my suspicion is worth...

I can't read the old one at all, but the new one appears to say EA1530A.

Great pictures by the way. What did you use for the even lighting?

I had a morning option on the world's best lighting equipment: the sun I couldn't get decent lighting in my office so I took the board out on my deck and shot there...

[diodo49]

Re: Vizio VA19L Won't Power On

Vizio, America's second best selling LCD TV brand, is now telling some broken set owners that their televisions cannot be repaired. If the set is past the 12 month factory warranty, Vizio advises owners to buy from them a replacement set ?

[budm]

Re: Vizio VA19L Won't Power On

I think your TEA1530A is bad. Pin 8 get the voltage from the main B+ 170vdc to kick start the IC, once the IC start driving the Mosfet which drives the transformer, the AUX winding of the transformer output will get rectified to produce the 12vdC for the VCC pin 1 of the IC, then the pin 8 will not be used once it starts running. Just think of it like your car, you need the batteries to start up the car, once the engine is running, the power will be coming from the alternator and the batteries can be disconnected and the car will keep on running as long as the engine keeps spinning the alternator.

[sysvr4]

Re: Vizio VA19L Won't Power On

Thanks budm, that's very helpful...

Based on your description of the problem, is it also possible that the transformer isn't working properly to provide that 12V to the IC?

Btw, new board works like a champ in the TV, tested it yesterday. I'm still going to attempt to fix this old board just for grins though...

[budm]

Re: Vizio VA19L Won't Power On

I myself never have to replace those power transformer in all my repair, I replaced lots of the high voltage inverter transformers due to high voltage and very small wire gauge. The power transformer uses very good size wire gauge. I doubt that you have bad transformer. I do not remeber if you have look at the startup cap c920 (22~47uf 50v) yet.

[sysvr4]

Re: Vizio VA19L Won't Power On

Yes, the startup cap had 0VDC across it. I don't have a capacitance tester yet, so that's all I've done with it so far.

Good idea to replace both the IC and startup cap while I'm at it?

[budm]

Re: Vizio VA19L Won't Power On

Do you have any cap at all to use for that startup cap?

[tom66]

Re: Vizio VA19L Won't Power On

If startup cap measures zero, suspect the charge resistors or the controller IC.

[sysvr4]

Re: Vizio VA19L Won't Power On

budm: No other caps currently on hand... well, except the one on the new board, but I'm not quite brave enough to pull that one off and use it to test

tom66: Thank you... if someone can provide a bit of guidance on where those resistors are and how to test them, I'll gladly check that too.

Thanks again guys...

[budm]

Re: Vizio VA19L Won't Power On

pin 8 Gets the kick start voltage from the main b+ which you indicated that it has about 170v so the feeding resistors are OK, that voltage on pin 8 feeds the internal current source which will charge up the start-up cap which is connected to the VCC PIN1, when that voltage reach Vstart (11V) on that start-up cap, the circuit will kick on (the current source will stop) and send out the drive signal at pin 6 which drives the MOSFET which drives the transformer, at that point, the AUX winding of the transformer (to the diode and the 2.2 Ohms resistor I have you checked earlier in post23) will be supplying the VCC to pin 1 to keep the IC running. Since you are getting 0V at VCC pin1, it means that that internal current source did not start the charge up process of the start-up cap. That is why I believe the IC is bad.
Since you have good board, what you can do is to do resistance reading comparison between the good board IC (TEA1530), MOSFET compared to the bad board.
To check the IC resistance, use pin2 (ground) as the ref point and measure all the pins of the IC with ref to Ground pin to see what you get on both boards.

[sysvr4]

Re: Vizio VA19L Won't Power On

budm, thanks again. Those kinds of explanations are so helpful, much more than the simple check this or check that... like I said, I'm trying to actively learn this stuff and I appreciate you taking the time to explain!

I haven't torn apart the working TV again yet to test the IC voltages, but you had asked earlier if I had any capacitors on hand... as it turns out I was going through some old drawers in the workshop today and found some.

Now, I have no idea how old these are, but they're all still new in packages... anyway, the startup cap is a 50V 47uF. What I have are:

1) 16V 220uF
2) 50V 4.7uF

Would either of those be helpful diagnosing a bad startup cap?

[budm]

Re: Vizio VA19L Won't Power On

One is too small, one is too high the capacitance.

[sysvr4]

Re: Vizio VA19L Won't Power On

Thanks... what range has a shot at working? Maybe I've got a dead board here from something else I can pull one from.

Actually, just found the following on an old xbox power board I have:

- 25V 47uF
- 25V 100uF
- 16V 1000uF

[retiredcaps]

Re: Vizio VA19L Won't Power On

Actually, just found the following on an old xbox power board I have:

- 25V 47uF

The 47uF 25V should be fine. The maximum voltage for the SMPS IC EA1530P is 20V DC and the startup is 11V DC as per

http://pdf1.alldatasheet.com/datashe...TEA1530AP.html

[retiredcaps]

Re: Vizio VA19L Won't Power On

Before you change the startup cap, you should measure the resistance as per budm post #33.

We have seen this SMPS IC EA1530 go bad before. That is, VCC is shorted to ground.

[tom66]

Re: Vizio VA19L Won't Power On

It's also usually OK to increase the startup capacitance, as the worst case is it takes a little longer to work when first plugged in.

[sysvr4]

Re: Vizio VA19L Won't Power On

Thanks again guys... I tested on the old board, and it *does* appear that VCC is shorted to ground on the IC. I can't compare yet to the new board because that TV is now in use in our guest room

As soon as I get an opportunity I'll compare the two and report back here, but it looks like I'll be ordering and replacing that IC soon.

Thank and Merry Christmas, everyone!