Sylvania lc320ss2 LCD TV keeps blowing fuse

[budm]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

That is the typical failure of that Zener when the MOSFET shorted out, I am surprised that the Source resistor did not burn open also. I am still trying to locate the diagram for this board, no luck yet.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

I appreciate the effort budm.
Yeah R608 was indeed defective with high resistance. It was one of the components I initially replaced. I was calling it "current sense resistor".

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Hi,
need a little help choosing a replacement diode. The shorted smt diode is a b5 sk2b, here is the datasheet
http://pdf1.alldatasheet.com/datashe...EKEC/SK2B.html

I'm looking at digikey and I'm not sure on what category this one falls to start narrowing down the results.

http://www.digikey.com/scripts/dksea...words=Schottky

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Can anybody give me a minute of their precious time to point me in the right direction here. I promise I'll do my homework once I'm given a little clue. I just wanna be extra careful in getting the right thing. With my beginner's knowledge is something I dont need.
thanks

[selldoor]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

You could try looking at this one
http://www.digikey.com/product-detai...STR-ND/2041487

Just for future info you might get more people looking at your threads if you
add pictures using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Great thanks, actually more than I asked for
So, it was under the rectifiers category.
Oh I had not idea about that, I'll try that next time.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Update guys.
I installed the parts today and the situation is still the same.
Some new things I found out.
If I remove the power transformer, I do get the right voltage on the filter cap, plus normal behavior of the power supply. So, I should be right in saying that my problem is on the secondary side?
It's not on another board since I've test with a load and the MPW only and the same happens.

I was trying a little trick of removing one leg of each secondary output diode and testing, in order to see if it'd give me some pointers but it did not.
Only thing I can think of is looking at the smt components on the bottom of the board tomorrow.

Regards,

[tom66]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

The main transformer forms part of the oscillator, so removing it would make the PSU stop completely, wherever the problem is.

[budm]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

"still the same" meaning that it is still blowing the fuse?

[Mark369]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

why dont you use a lamp in place of fuse, that trick help me out alot.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Hi,
I guess yeah it's still blowing the fuse although I have been using the light bulb trick all the time to prevent it from not only blowing the fuse but also other components like the power FET as it happened before.

I've been trying different things with my limited knowledge.
Taking voltage readings from different points of the board all voltages are lower than what is labeled. Then again the tv doesnt turn on, all this happens while in standby.

Doing a resistance test technique from that smps ebook the only output line I see a wrong reading is from the negative line coming from a zener diode on the secondary side which shows a low resistance value. So I'm just taking a look at that now to see.

Also there is a test point (from a jumper) where I should be getting 24v and I'm getting nothing. Right there next to a ceramic filter. I dont have a way to test the ceramic filter right but I doesn't look bad and after removing it and testing everything continues behaving the same way.

This is a training for me, have been at it for various weeks on and on. Hoping to learn something

Thanks guys.

[Mark369]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

you should remove the fuse and get a old lamp cut the plug off and place one wire on one side of the fuse holder and the other wire on the other side of fuse holder. no fuses need to be in at the time so no blown fuses.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Pardon me if I was not clear.

I'm using the light bulb trick ever since I learned about it.

My point is that the tv is still behaving like it still has another shorted component, when I plug it in (with the light bulb across the fuse). Would love a service manual for this one

[budm]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

OK, so the lamp lights up brightly then? I have gone through the troubleshooting MARK369 try to find the shorted out component by lifting one leg at a time, but we have the service manual for his TV, it took us over 80 threads to find the short.
https://www.badcaps.net/forum/showth...t=24444&page=5

[Mark369]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

This tv is sold under the emerson name and Sylvania as well if that helps still trying to find manual for you.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Yes the lamp is very bright.
You know I've done a few things and dont make seance.
I tried a trick of desoldering one leg off of each of the 6 output diodes, one at a time, then tried plugging the tv in after each leg lift to see if it'd tell me in which line is the shorted component. But the same thing continues happening where the light bulb is still bright with all six attempts and the voltage on the filter cap is 2vdc. Which would make me think that my problem is on the primary side.

On the other hand if I remove the power transformer, the light bulb doesn't light up and I get my good voltage (168vdc) on the filter cap. Which makes me think my problem is on the secondary side.

The output voltages on almost or all the test points are below their values.

Another thing, if I check with a clamp ampmeter across one of the wires from the lightbulb I get .7 amps, just though I'd mentioned, and of course 2vdc on the filter cap.

Oh I need a variac so bad. Just lost one auction to a sencor pr87 which seems is the best option out there.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Mark369, appreciate the effort.
Yeah I got the equivalent model numbers from Sylvania, Emmerson, Phillips and Magnavox listed on the first page of the thread
Here they are again.

Emerson LC320EM2
Emerson LC320SS2
Magnavox 32MF301B/F7
Philips 32MF301B/F7
Philips lc320ss2

[budm]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

I think the short is in the primary side of the circuit. If you remove the MOSFET, will it still light up the lamp?
I also search using all those models without luck.

[Beowulf]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

Thanks,
I'll try that first thing tomorrow.

[Mark369]

Re: Sylvania lc320ss2 LCD TV keeps blowing fuse

I found this to bad it won't help much.