VX42L Vizio 42" TV - only amber / white light, no power

[sansonet]

I'm trying to fix Vizio 42" TV, initial problems - bad big 450V capacitor, blown fuse, bad big MOSFET STW21NM60N which was causing fuse blow http://www.mouser.com/ProductDetail/...UzZdMkjg%3D%3D
Replaced all that, got amber light and it turns to white when I'm pressing power button. Nothing else works. No 12 / 24V, only 5V. Voltage reads 165V on big capacitors with amber or white light. I tested all caps with capacitor tester, resistors, mosfets and diodes on heatsink, diodes on board - all tested good. Not sure what else to do. I checked treads about this model here - don't see anything with similar problem.

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

What DCV do you get at PSON pin?
If PSON is >2.5V then the Voltage on the main filter cap should jump up to >360VDC, if not the PFC Voltage booster is not working.
It the MOSFET for the PFC circuit, if it is, then more likely the PFC Control IC is also damaged. You need to get the PFC Voltage booster to work first.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

What DCV do you get at PSON pin?

I'm getting 3V with main connected, but I also tried with main disconnected and applied 3V to it (using set of 2 aaa batteries and jump wires) but results still the same. Big mosfet that I replaced is located on first pic, heatsink in center of board, middle part of it near screw hole.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

then more likely the PFC Control IC is also damaged

I never dealt with those - can I test it to confirm it, also what are chances that replacing this IC will fix it? So far I keep fixing one problem just to find another one after that...

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

When the Power MOSFET shorted out, it will usually take out the Gate drive output of the IC plus any components (resistors, diode) connected between the Gate drive out put pin and the Gate pin.
There is no 100% test on the IC to ifnd out if it is good or bad for sure.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

Is it correct chip? Also what components , connected to it I should check / replace?

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

"bad big MOSFET STW21NM60N" What is the designator of this MOSFET? Q????

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

Yes, Q801 - it's printed on another side, you can see leads on bottom of board (pic #3 in first post), it's middle part under round plastic pin

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

Q801 is for the PFC.
OK, it is either IC801, or 802, more likely to be IC801. You will need to get the P/N as printed om top to get the spec. sheet.
You also need to check the resistor and Diode connected to the Gate pin of that Q801.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

Here are pics, I see number on IC802 clearly, its DAS001, but print on IC801 is hardly readable, specially last digits

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

One more pic, I think it's L6562D http://www.mouser.com/ProductDetail/...BjkbrTAw%3D%3D

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

L6562, that is the one for PFC.
Check the resistance of GND pin against all other pins and report the readings, no power to the TV of course.
http://www.shopjimmy.com/vizio-0500-...er-supply.htm#

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

I'm not sure where is top and where bottom of this chip, but if I take part with IC801 print as top part, i'm getting no readings on all pins with GND, COMP pin had resistance initially but numbers was raising for few second and then disappeared.

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

https://www.badcaps.net/forum/attach...1&d=1422898205

pin 1 is the bottom left, you can see round dimple next to the 'ST'.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

OK, here are readings:

INV - 10.24K
COMP - 0
MULT - 20K
CS - 1K

VCC - 1.54M
GD - 10K
ZCD - 38.8M

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

Pin 2 and Pin 5 do not look right. I would replace this IC.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

OK, I can order one to replace it, but before I'll do that -is there anything else I should test / replace?

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

I checked some boards I have laying around, found one I was never able to fix and got cheap replacement instead, looks like it has the same chip - but since it is not working board, I can't guarantee it's a good chip. But here are readings - if this looks good, I could try to use this one instead of ordering it, I don't mind to order, they are cheap, but trying this one will be faster

INV - 19.7K
COMP - 0
MULT - 19.9K
CS - 0.47K

VCC - this one keeps changing, goes up or down
GD - 10K
ZCD - 12.9k

[budm]

Re: VX42L Vizio 42" TV - only amber / white light, no power

I do not want to use this unknown condition IC since you can take a chance of damaging the new MOSFET.
This second IC sure shows different reading from the original one so I do not know if this second one is good or bad.
Another measurement you can do is to test the DC Voltage between the VCC pin and the GND pin, you must be real careful not to let the probe slip on you and do not touch anything with your hands.
I have a feeling that there is an open circuit on the VCC pin back to the power supply source that supplies the Voltage to run the IC, that section may be damaged also.
The resistance on the VCC pin should show low resistance first due to the filter cap connected to the VCC pin is charged up by the meter and then the resistance should rise into K Ohms range.

[sansonet]

Re: VX42L Vizio 42" TV - only amber / white light, no power

OK, I'll just wait longer to get new one, it's not very big emergency anyway