Vizio E461-A1 (lightning strike)

[alecjahn]

On the bench today (well, technically my bed...) is this 46" Vizio. Fairly recent model (quite thin bezel to note) LCD with LED backlight. Freebie from a friend's grandmother.
We had a week or so of constant thunderstorms here in Kansas and this was a casualty of a lightning strike.

I THINK I have this progressing properly but I just want to make sure I'm not missing anything.

Initial symptom was a completely dead set, naturally. No lights, no smoke, no mirrors.

The mains fuse (5A slo-blow, ceramic) had failed. I popped in a glass 5A slo-blow and it immediately blew.

As per recommended tests via other threads on this forum, I checked the bridge rectifier and pins 1 & 4 were shorted. Before pulling the part I started checking diodes and transistors (etc), and found that Q9801 had pins 2 and 3 shorted. As a quick test solution I clipped the lead on pin 2 (Q9801) and it still showed shorted. Then rectifier 1 & 4 were no longer shorted. Progress!

The part is a 24NM60N. STF24NM60N to be exact. Datasheet link

All other similar components seem to test fine with the same continuity check. Naturally I didn't find one to salvage from any of my junk boards nor do I have the knowledge to even consider finding an "equivalent" to try out. So, I've got one on order.

It seems I am, so far, setting myself up to be home free. Right?
The part was ordered from Digi-Key and should be here either Saturday or Monday.

I added a mediocre photo for reference though I doubt it is needed.

Thanks,
-Alec

P.S. - I'm a little fascinated by the measures taken to keep the set as slim as possible. I haven't worked on one this new before. The transformers are as thin as pancakes and the capacitors are such specific sizes, either also flat or extra long+skinny and set parallel to the board. Very cool.

[alecjahn]

Re: Vizio E461-A1 (lightning strike)

Well dang. The part arrived and I installed it. I plugged it in and the fuse didn't blow... for about 4 seconds (previously it'd blow immediately).

So:
-replaced part
-fuse blew, albeit delayed
-replacement part is now shorted just as the original was.

I checked for shorts after I installed the part and before I applied power. So, something else caused the 24NM60N to fail, again, which perhaps prompted the fuse to blow.


hmmmm.


I found what appears to be the schematic on elektrotanya (only a slight difference in number, I assume similar enough for this task).



(and, heck, here's another one that could be close/useful )

Attached is a screenshot to help find Q9801 and might provide enough info anyway.

[budm]

Re: Vizio E461-A1 (lightning strike)

That is the Power MOSFET for the PFC Voltage booster circuit, when in doubt I always replace the IC that drive the MOSFET at the same time since shorted MOSFET can damage the IC at the same time. You also need to check any components between the IC GATE drive output and the GATE of the MOSFET for damages.

[alecjahn]

Re: Vizio E461-A1 (lightning strike)

That sounds promising.
Took me entirely too long just now trying to find that IC...
whaddya know, it was on the bottom of the board... Dur.

Anyway... unfortunately for me, that whole area of the circuit seems to be all surface mount stuff which puts a damper on easily pulling and checking components.

How might I go about testing the IC? So far, with my meter on beep-beep mode, there's a short (~10ohms) between VCC and GND.
Seems like that could be the fault of ZD9107 as well, so I lifted one side of it and the short (on IC) is still there. ZD seems to check out fine while lifted.

So... replace the IC9801 and Q9801 simultaneously and give it a go?
I should still lift the IC and check it again (and its pads), right?



http://pdf1.alldatasheet.com/datashe...A20113ASP.html

[budm]

Re: Vizio E461-A1 (lightning strike)

Something like this I would just replace it, no good taking a chance of blowing another new MOSFET.
You should remove that suspect IC just to be sure that the shorts go away.

[budm]

Re: Vizio E461-A1 (lightning strike)

BTW, when TV is hit by the surge/lighting the parts that get damaged are the HDMI chips, so you should inspect the main board really well, the tuner can also be damaged as well.

[alecjahn]

Re: Vizio E461-A1 (lightning strike)

Sounds like a plan. Unfortunately, neither DigiKey or Mouser stock that IC. All I can find is one eBay listing from China.
EDIT: Missed your second post. I'll do that as well, thanks for the info. Gotta remove a big shield first, which will be a pain. Everything in plain view looks fine.


I appreciate all of your help, budm. Thanks!

[alecjahn]

Re: Vizio E461-A1 (lightning strike)

Good news!
I ordered the 24NM60N and R2A20113ASP (well, had to get 5x each) from eBay. They arrived a couple days ago and I installed them yesterday. Unfortunately the fuses I ordered hadn't arrived yet. I waited to see if they were going to show up today. They didn't.
So I went to the hardware store and paid the $6.50 for two of the dang things (grrr) so that I'd have something to do today.

Whaddya know, it works! Despite my less than stellar SM work.

As an added bonus, it appears I got very lucky - all three HDMI ports work.
(The picture turned out looking ugly, but that's just my crumby camera - in reality the image is very nice!)

Sweet!

Anyway, thanks again for your guidance, budm. It means a lot to know y'all are around to help schmucks like me.