E390vl help with regulator testing

[audiofreak19]

Re: E390vl help with regulator testing

Will I be able to test the resistance when it's removed from the board like that. And not connected at all to the tv.

[budm]

Re: E390vl help with regulator testing

We want to test resistance of the output copper pad and the chassis ground without having the IC on the board, we are not trying to measure the resistance of the IC.

[audiofreak19]

Re: E390vl help with regulator testing

Ahhhhhhhh. That makes so much sense. Super blonde moment. Haha

[audiofreak19]

Re: E390vl help with regulator testing

So I removed the regulator and the big pad or output pad still read 1.1ohms. Here is a pict of the board with the regulator removed.

[ecking767]

Re: E390vl help with regulator testing

So I removed the regulator and the big pad or output pad still read 1.1ohms. Here is a pict of the board with the regulator removed.

you can remove the inductor to confirm (see picture) if your CPU is fried. This will isolate the regulator output from the CPU.Then measure the output again. I only did a visual trace of that output of that regulator, you may need to confirm where that regulator output is feeding by using your multimeter in continuity mode. also try testing the cap.

[audiofreak19]

Re: E390vl help with regulator testing

So if I remove the inductor. I should get the same ohm reading? What would it say if the CPU was bad.

[budm]

Re: E390vl help with regulator testing

Is there a small brown rectangular ceramic connected to the big tab of the IC also? Removing that FB (ferrite bead) from the circuit will help us isolate the load from the output pad, there may be more than one load that is connected to the output pad, removing that FB is the start.

[audiofreak19]

Re: E390vl help with regulator testing

The only think small I can see that's near the output tabs is that very time cp18 if you look just left of the 3 pads.

[audiofreak19]

Re: E390vl help with regulator testing

Ok I see the fb it's what eclogues labeled in his image. I will remove that and take another resistance measurement of the big tab in ref to ground.

[audiofreak19]

Re: E390vl help with regulator testing

Wow I ment ecking

[budm]

Re: E390vl help with regulator testing

CP18 looks like for the input. Typical kook up of the regulator IC will have electrolytic cap with small ceramic cap in parallel for the input pin and the same for the output pin.

[audiofreak19]

Re: E390vl help with regulator testing

Ah ok.

[budm]

Re: E390vl help with regulator testing

BTW, the small brown ceramic cap usually is MLCC (Multi Layer Ceramic Capacitor), when it failed, it failed as shorts circuit.

[audiofreak19]

Re: E390vl help with regulator testing

Ok so I took the small ceramic cap out the fb whatever. And measured the resistance between the out put pin and the chassis ground without the tv plugged in and got 5.78 mega ohms. So I'm guessing the CPU chip is bad. Eh?

[budm]

Re: E390vl help with regulator testing

That or any other components that are connected to that section.

[audiofreak19]

Re: E390vl help with regulator testing

What would you say to check next. I might just buy another main cause I found one on ebay for 35. But I like learning how to test these things and how each of these components work.

[mmartell]

Re: E390vl help with regulator testing

Remove CPU see if short goes away )

[budm]

Re: E390vl help with regulator testing

There has to be another MLCC cap after the FB, I would look for that and then remove it to see if shorts will go away.

[audiofreak19]

Re: E390vl help with regulator testing

And sorry for my ignorance I'm having a blonde moment. But a short on my multimeter would be a lot of resistance correct?

[audiofreak19]

Re: E390vl help with regulator testing

Also was the FB thing the MLCC cause there is a very small cap next to the FB thing I removed.