Vizio SV320vxt popping fuses like it made it up.

[shwsrvcs]

Hey all. I am hoping to 2 get some advice/help on this model. the one that I have is blowing fuses, the caps on the power board and the power board look okay to me. The main board, not so much... It looks to me like a lot of blown cap's on that but I never see many pics of blown caps oF that type. I have highlighted them in the attached images of the main board.

I know that the more info I have I can better form an opinion so with that in mind, I also took a bunch of other pics of the power and main boards with my camera in different lighting and those can be seen at.

http://www.avdigitalsound.com/jackstin2

I am waiting for and order of capacitors to arrive that I think will do the trick, but just in case. do any of you know what the numbers are on the top? I assume it's the same as electolytics but I would like to be sure before I go popping them off and putting on incorrect spec replacements...

Any help you guys can offer would be and incredible help!

Dave G

[tom66]

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

Thanks for the good pictures.

The capacitors look okay. I have a board from an LG which has caps which look a bit like that (vent appears to bulge) but SMD caps do that (they all test okay.) I believe it's due to how they are manufactured.

If your TV is popping fuses, it's more likely to be the power supply than anything else. Capacitors would be unlikely to cause this; common failures are the bridge rectifier and MOSFETs - both of which are relatively easy & cheap to replace. Can you supply pictures of the PSU?

[multimeter]

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

highly likely its the (in order) bridge rectifier,followed by a shorted main primary cap,then the mosfets,test in that sequence

[multimeter]

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

down shot of the power supply please?

[shwsrvcs]

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

Thanks for the quick replies!

Here are some pics of the powerboard. thanks again for you assistance! Hoping with some time I'll be able to do likewise for others here.

I'm looking forward to checking back in when I get back from a house call for a client.


cheers! to you all!

dave G

[shwsrvcs]

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

I'll be testing those tonight as soon as I fer home!

[selldoor]

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

Its a long shot but if the tops screw off the heatsinks can you do that and make sure they are not touching anything underneath. I am asking as the solder at HS1 has brown (probably flux) but no other joints have.


ALSO pins on IC901 look awfully close - do they touch.
I dont know if they are meant to.

[tom66]

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

Are you referring to the T4AH fuse on the board, when you say it keeps popping fuses?

[shwsrvcs]

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

Hello again. I checked out the bridge rectifier and found it in bad form. Using my multi meter to test diode (ohms) and also for continuity. Well no change on the level in either direction (i posted the readings for the same posts on my multimeter in both directions below, I checked the IC901 pins and they all appear to be far enough apart (also images below) and I removed the heat sinks to view no evidence if any objects or odd connections. Yes the fuse was the T4Ah main ceramic fuse, although, I just noticed I had put in a 5a after the last one blew last week.

So with that bridge rectifier apparently done for and perhaps at the root of this poppin and lockin the TV has been doing... it's looking like a trip to MarVac in Costa Mesa after I pick my son up at school in a hour or so

[shwsrvcs]

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

oops forgot to resize those images

[tom66]

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

The bridge rectifier is a common failure point in TVs, it seems. Replace it with a device similar to GBU4J, a 600V 6A part.

(If you're sure you're only going to use it in the US, you can get away with a 200V part, but going for a higher voltage rating will improve the safety margin and make it less likely you'll need to replace it again.)

[budm]

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

You may want to build one of this short indicator so you will not keep blowing your new fuses and new components, it is basically put the lamp in series with the load, for your TV, you can use 100 ~150Watts LAMP should be enough to see if the light comes on real bright and stay bright, come on bright for a second then dim down if it is OK. Since the bridge and the main DC filter cap are always on the minute you plug the TV into the outlet (you not have to turn the TV on), it lamps stays brigtly lit then you have problem.

[shwsrvcs]

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

ah ha. thats a really good item right there. I'm going to make that for sure.

I got side tracked till now for a laptop monitor repair, but I'm heating up the Weller right now and am going to install that rectifier next. I'll report back again with the outcome.

Thanks again for all the assistance!

DG

[budm]

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

I would Ohm out the + and - of the bridge after you install it, you should see the meter shows real low Ohm but then the resistance should rise up (as the cap is being charged up by the meter) into K Ohms range.

[shwsrvcs]

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

I would Ohm out the + and - of the bridge after you install it, you should see the meter shows real low Ohm but then the resistance should rise up (as the cap is being charged up by the meter) into K Ohms range.

O came back here to my desk to grab a power cord to test my work, and so I tested this, and it did drop and build back up. All right! I thought.. here we go.

ffffip

not as loud as the pops before, but just a mild sound and a bit of glow at the incoming end of the fuse as it became open... i'm going to check that bridge rectifier again to make sure this new one is still working as it's intended and then I should check the mosfets? no, that main cap... I'm going to test that main cap... i'll do that when I return from getting something to drink at cvs..

drat.
DG

[shwsrvcs]

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

oh wait did I say build back up on that ohm test? I took the board back off the panel and brought it back to the bench... I tested that again and noticed that, what I tought in haste was the charge building was really the charge leveling. it drops to zero at first but then after an initial change back up, settles into 0.2 reading that stays steady. which is what the multimeter does when the two terminals touch together.

I tested ohms on all the mosfets under the heatsink covers on the primary side

all are tested with the negative on the screw at the top and the pins below left to right

board#}{ Pin 1 }{ pin 2 }{ pin 3 }
Q801 }{ 1.3 }{ 0.2 }{ 0.2 }
Q802 }{ 2.590 }{ 0.5 }{ 0.5 }
Q601 }{ 4.45 }{ 0.7 }{ 4.45 }
Q603 }{ 2.421 }{ 4.41 }{ 0.5 }

these are all so non-uniform, I must be measuring something wrong. I'm going to research as soon as I wake up in the morning.

Dave G

[multimeter]

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

oh wait did I say build back up on that ohm test? I took the board back off the panel and brought it back to the bench... I tested that again and noticed that, what I tought in haste was the charge building was really the charge leveling. it drops to zero at first but then after an initial change back up, settles into 0.2 reading that stays steady. which is what the multimeter does when the two terminals touch together.

I tested ohms on all the mosfets under the heatsink covers on the primary side

all are tested with the negative on the screw at the top and the pins below left to right

board#}{ Pin 1 }{ pin 2 }{ pin 3 }
Q801 }{ 1.3 }{ 0.2 }{ 0.2 }
Q802 }{ 2.590 }{ 0.5 }{ 0.5 }
Q601 }{ 4.45 }{ 0.7 }{ 4.45 }
Q603 }{ 2.421 }{ 4.41 }{ 0.5 }

these are all so non-uniform, I must be measuring something wrong. I'm going to research as soon as I wake up in the morning.

Dave G

the readings you are getting on the mosfets sound like they are still in circuit?,have you removed them then tested?,the .2 you seem to be getting from the primary cap sounds as if it is shorted,and definatley use the suggestion from budm bout the series lightbulb tester,if you have a esr meter check the primary cap ,if you dont then just straight replace that cap with the correct spec ,normaly if there is a dead short the fuse will be very black if its a glass fuse,if it is just age related failure then the glass will be clear and the fuse wire still visable inside the fuse,replace primary cap 1st.

[budm]

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

If you keep re-solder and solder in the fuses, sooner or later the traces will be damaged. Take the cap out and Ohm out the two pads where the cap was connected to to see if you read low Ohm also.

[shwsrvcs]

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

Okay. on the fuses, I've been replacing them via the little cup connections exactly for the reason that I don't want to mess with the solder points.

I replaced that q801 mosfet and viola! the unit is no longer blowing fuses! the amber light is on, and then it turns white when the power is pressed!

it's just...

no screen turns on.. and there is not indication of sound.. although with no signal... there couldn't be any

checked the inverter board and it looks like this attached.

[multimeter]

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

Okay. on the fuses, I've been replacing them via the little cup connections exactly for the reason that I don't want to mess with the solder points.

I replaced that q801 mosfet and viola! the unit is no longer blowing fuses! the amber light is on, and then it turns white when the power is pressed!

it's just...

no screen turns on.. and there is not indication of sound.. although with no signal... there couldn't be any

checked the inverter board and it looks like this attached.

now the tv fires up,now check ALL outputs against there legends to make sure supply is healthy,if any arnt investigate why,a white screen could be a tcon smd fuse has blown,psu 1st