Vizio SV320vxt popping fuses like it made it up.

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

I took the time time walk away for a bit and come back fresh. I really appreciate all the help I've received here and this forum is the absolute best I've seen in a long while.. at least 10 years of bbs/forum usage.

I tried the last couple suggestions and all the ceramic fuses come back as good. I went thru again today and tested the voltages coming from the main board back (PSON) and it shows an increase when the power is turned on, the amber light in the front turns white when the power is turned on, the power will stay on (amber light is white) until it is turned off.

Checked to find if the video is being sent to the screen but I am unable to see any thing while using my led flash on my phone or incandescent flashlight.

so I've got power all the way up to when it comes back to the switch mode power, but at that point from what I can tell, there is no signal to the screen and no power to the backlight. I really wish I could have figured this out but I think I'm out of time, well... yes, I'm out of time,

The person I'm working on this for has been and is still being very patient but realistically, Im thinking maybe.. I've taken time in this repair that would better used by maybe ordering the 60 dollar board on eBay and just replacing it?

Really I wish there was more of standards type thing going on at the component level, if not for all brands, at least across each brand. I had 4 vizio's thru here last week and each one of them has it's own way of connecting between boards, the ccfl's. I understand the tech is ever expanding but maybe with the advent of led back lights the need for just downright funky boards in each model in a product line can give way to something more modular and interchangeable.

[selldoor]

Re: Vizio SV320vxt popping fuses like it made it up.

There are also two ceramic fuses on the main board F1 & F2 - have you tested those?

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

Hi I have just been reading through the thread and have had what I hope is a eureka moment.
In post 19 there is a picture of the inverter board and there is a white sm fuse. I cant see that this is referred to in the text and wonder if you have tested it at any time?

You know, I took a break yesterday to write out my letter of resignation from the porn biz to jump into the deep end here in this line of work. (seriously, i've been webmastering in porn since 99 but its a dead industry now) but now I'm getting ready to test another board for another vizio here. I'm going to pull that back on the bench as soon as I get this testing finished.

Thanks for the idea!

DG

[selldoor]

Re: Vizio SV320vxt popping fuses like it made it up.

Hi I have just been reading through the thread and have had what I hope is a eureka moment.
In post 19 there is a picture of the inverter board and there is a white sm fuse. I cant see that this is referred to in the text and wonder if you have tested it at any time?

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

I took these pics earlier then walked away from it for a day to try another avenue hopefully be successful this time.

Here are 4 views of those caps, they do look odd at certain angles, but when I look closer then they look okay...

[budm]

Re: Vizio SV320vxt popping fuses like it made it up.

By the way, my post #41 with the attached PDF, I also circle some caps that look like they have domed tops, did you verify that, may be its the distorted pix.

[tom66]

Re: Vizio SV320vxt popping fuses like it made it up.

Check the PFC diode on the primary side.

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

The two main DC caps (two long brown cap 450VDC rating) are in parallel to get enough filter (they are selected for the amount of the AC ripple (riding on top of the DC) that the circuits are allowed to accept).
This power supply board has PFC Voltage booster circuits, when the TV is OFF, the DC on that cap should be around 165~170Vdc, when the board gets the PS_ON signal from main board, the voltage on the caps should go up to around 390~400Vdc.
Most TV in the last 2~3 years use PFC circuit to get power factor as close to 1 as possible.

Ohhh ok. I see that! so let me bring that board back here to my desk...

dang it...

I am so dumb. I touched the probes together cuz I decided to see if the voltage had changed for either of the two, with the additional info on the pdf, it was clear as water how those two interacted with the next part on the board.. and those mosfets above them.. but anyways... they touched and there was that distinct pop of electricity. now the caps don't read any voltage at all, the main fuse, beep on the continuity setting, but now the meter reading fluctuates while it beeps... damn it.

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

okay.. now that I've got them both connected properly they both read 167.6 with the power on standby and 163,4 when the vizio light is illuiminated.

[budm]

Re: Vizio SV320vxt popping fuses like it made it up.

The two main DC caps (two long brown cap 450VDC rating) are in parallel to get enough filter (they are selected for the amount of the AC ripple (riding on top of the DC) that the circuits are allowed to accept).
This power supply board has PFC Voltage booster circuits, when the TV is OFF, the DC on that cap should be around 165~170Vdc, when the board gets the PS_ON signal from main board, the voltage on the caps should go up to around 390~400Vdc.
Most TV in the last 2~3 years use PFC circuit to get power factor as close to 1 as possible.

[cashkennedy]

Re: Vizio SV320vxt popping fuses like it made it up.

((The DC power on the primary side is relative to how much it is amplified before the bridge rectifier and whether its US 110v, or europe 220v. Modern designs that can handle european input are usually made with 600v caps i believe.)) nevermind im probably wrong on this, the common voltages for these caps must be slightly lower, perhaps the 450v is the common one for europeans 220v capable designs.

[ben7]

Re: Vizio SV320vxt popping fuses like it made it up.

okay, the first big cap 160 dc
The second big cap 0 dc

Um, please read those again, they are in parallel, so they should both read the same!

-Ben

[ben7]

Re: Vizio SV320vxt popping fuses like it made it up.

Thats odd that the caps are 470 volt, but if you know the voltage that they will run at, you might be able to use 450 volt ones which are more common. I cant think of any caps that go above 450v

-Ben

[cashkennedy]

Re: Vizio SV320vxt popping fuses like it made it up.

Im pretty sure for the huge dc cap you can replace it with any voltage from 470v - 600v.

I think i read somewhere also that the capacitance wasnt very important so long as it was rather low.

So if you see something in the range of 470v-600v, with 65-70uF capacitance, then you should just use that. You might have to modify the way its attached / mount it sideways to get it to fit.

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

okay.. no 68uf 470v caps here, in all of the different component electronics, a the LCD tv's here, all the power boards --- i dunno.. maybe just 10 or 15 total, but seiously.. in all of those, I could not find a single instance of capacitors being of the same ratings.. not a single one. I don't understand that. perhaps ill ponder that tonight for a while. right now i'm heading to MarVac, with any luck they well have that size.

do any others work if they are done in series or in parallel? and if so. is it the voltage to worry about or the microfarad rating or both and if both how do they interact when wiring up in series or in parallel? I think I need to get some schooling going on here.. this is too many questions for a board, and youtube aint helping me with 10 year old trying to show me how to solder by plugging the damn iron into the wall...

DG

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

okay, the first big cap 160 dc
The second big cap 0 dc

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

and so to test the caps, as there are two on this board. what can I do to ensure a proper and accurate reading?

If you have them off the board not a lot (unless you had an ESR meter)
You can test for shorts and that's about all.

i'd only taken them off the board to get the right numbers (which were printed right where they were glued to the board. when they were on the board, they were looking okay though and they ohms seemed to be working okay, but i never checked for the voltage and after i got the numbers I put them back on the board since they weren't bad.

SO they are on the board, I can measure them, and I will... I was hoping for a little procedural assistance to measure, as in series, individualy, etc... and in the case if these results come up that they are both within spec, what is the next item? to review.. the models has:

1 would not power - blowing fuses... fixed, no more fuses have blown
2 vizio symbol lights amber and turns to white, but no picture or audio -
this was where the suggestion for the big cap testing was made as it was confused that the white light meant the lcd panel.


This was where I went off to try and build that light bulb piece and then thought, well , I may as well buy the caps in case they are bad just in case.. came back without the switch for the lights and without the caps since they didn't have the right one.

with nieither in hand, i checked the voltage as suggested in the other messages in line and viola, now here I am. About to test the voltage on the caps.

back in a few with the results.

[selldoor]

Re: Vizio SV320vxt popping fuses like it made it up.

and so to test the caps, as there are two on this board. what can I do to ensure a proper and accurate reading?

If you have them off the board not a lot (unless you had an ESR meter)
You can test for shorts and that's about all.

[shwsrvcs]

Re: Vizio SV320vxt popping fuses like it made it up.

I think you should test the voltage across the BIG cap as there seemed to be some doubt earlier that it was operating correctly.
Meter on 600V DC and observe the polarity - HIGH voltage so great care.


Did you do this before you removed it?

no I had not because actually after re-reading the posts inline, I realized that your mention that there was mention about it being bad earlier was in fact the first mention of the possibility of the big cap operating incorrectly in the post. Kinda like foreshadowing but in a less foreshadowy way. But it did plant the idea that it could be bad

Moreover, this board's big cap is 2 smaller caps acting as the big cap side by side. I was heading out to fry's to get a couple things and thought it may be nice to get those 2 "just in case" but guess I thought a thought too soon as the specs for them were glued on the board face down by the glue they put in for assembly time

I cut them loose and then read the bottoms 68uf 470dv... which frys's does not carry, not sure about good ole tandy co. they closed before I got there.. I'm going to Marvac as soon as it opens to try and get em.

But with that in mind, for the set of reading in my last post were done by me indoors with controlled conditions and yest with the power/hold button pressed (vizio white light in front on) and off (amber vizio light lit.)

and so to test the caps, as there are two on this board. what can I do to ensure a proper and accurate reading?

Thanks

DG

[multimeter]

Re: Vizio SV320vxt popping fuses like it made it up.

errr. didn't get that light fixture quite done, but I am gonna try again in the morning.. I did however find the voltages from the multimeter.. and they are with both the power button pressed and also in standby..

.3 for PSON
3.2 for 12v
5 v for svsb

and still no fuses blown since ever.. oh.. I pulled the main caps and checked em with the meter, they both dropped and then chlled at low reading. I decided to try and replace em just in case, but nope... no 68uf 470V at frys. will try marvac in the morning..

.3 for the ps-on dosent look good...or 3.2 for the 12v...,that with power on?,and standy button pressed for on?