Vizio VOJ320F1A Dead - no amber light

[RJE]

My tv went dead the other night while my wife was watching it. Just died! I took it apart and thought it must be the power board fuse. No - it was OK. Took readings at the 5 12 and 24 volt outputs. Only got a 5.18 volt reading - no 12v no 24v. Figured it must be bad board - I couldn't visually see anything wrong. But before I ordered a new power board I came across this forum and realized it must not be getting a "power on" from the main board (thanks guys for saving me from that expense). I then traced the wire(s) to the main board from the power 5v and discovered that the little surface mount fuse is bad (3amp). Didn't know they made fuses that small. My questions:
1) What should I check to determine what caused the fuse to blow?

2)What kind of fuse do I need to replace it with? It looks like it a Littlefuse, but I don't know if
it's fast blow, slow-blow or ? I found a part online 448.003 that's a fast blow but not sure.

3) Where is a good place to get them in small quantities?
Thanks.

RJE

[budm]

Re: Vizio VOJ320F1A Dead - no amber light

The fuse may be blown due to fatigue due to high in rush current, you can check the resistance between the Bottom end of the fuse (the output side of the fuse, the top end is connected to the white connector which is the input side of the fuse) and GND to see if it shows very low resistance (<100 Ohms).
That F1 Fast-blo is made by LittleFuse (LF). You can use 3A fuse with legs instead, I use PICO II fuse.

[RJE]

Re: Vizio VOJ320F1A Dead - no amber light

Thanks for the quick response budm. I managed to find some PICO II fuses and managed to solder one to the board, with high hopes. Unfortunately I guess I was way too optimistic. That fuse also burned out. I went back to test the output side of the fuse as you suggested and found it does have a reading to ground of less than 100 ohms. I did not see it before because it only lasts a second or two and then reads infinity. I don't have any idea what would cause that. Maybe I should just get a new board or new tv.

[RJE]

Re: Vizio VOJ320F1A Dead - no amber light

BUDM or anyone else- I would like advice on how to proceed from here. I don't understand what could be causing the reading to ground to be low resistance for a second and then go to infinity. If you think it will be a tedious and lengthy process to track down the problem, then probably best to buy new board. If you believe it would be fairly straightforward, please provide guidance. Thanks.

[budm]

Re: Vizio VOJ320F1A Dead - no amber light

'That fuse also burned out. I went back to test the output side of the fuse as you suggested and found it does have a reading to ground of less than 100 ohms. I did not see it before because it only lasts a second or two and then reads infinity.' I am little confused on your reading, so it shows low resistance reading and then it goes infinity?
But since it blows the new fuse, so to trace out for shorts will be very time consuming process especially when we do not have the diagram, it can be done but take lots of times.

[RJE]

Re: Vizio VOJ320F1A Dead - no amber light

Thanks for your quick response, budm. I appreciate all your help. I don't think it's worth spending a whole lot of time on it. I will either get a new main board or new tv. Thanks again.
RJE