Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

[budm]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

There are 5 of them in your pictures. F1 ~F5.

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

yea i checked em all and theyre all fine

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

=
and i think i will try some reflowing of some joints. what is the best way to do that? just heat them up and let them cool again? or actually remove the solder and resolder everything?

Well either really. I try to remove some of the old solder, then add some leaded solder, reheating it all then letting it cool. If its just one or 2 joints I would remove as much of the old solder as I could and re solder.

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

ok i reflowed all the joints (easy way, just heated them to melting and let them reset) and still the same. cant get backlights to turn on at all.
what else can i test on the inverter? and how can i test the lamps?

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

You could test each of the mosfets on the inverter board.
Test the resistance of secondary windings on all the transformers - on the same type ones the results should be within 3 % of ech other.

Bulbs - if you have any spare ones substitute those and see if it stays on.
If you dont you could make up some from cfls - see Budms signature links.
EDIT
Reading back I dont think the current problem is related to the bulbs or the transformers.
I think you threw off initially by saying the lights flashed when you tested the fuses.
Then it seems you were not actually testing fuses but ceramic caps so the flashing on was
possible then in our minds carried to the proper fuses whereas the problem is likely to be with the ceramic caps - they do get brittle and it just needs a hairline crack and they are dead.
So I think you need to check them again only thing is as they are in blocks of 3 I would be surprised if that stopped it working. You could also test all those 0 rated resistors
they can blow just like fuses

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

thanks for the ideas. yeah i did mess up there when i said i was testing fuses but they were caps :/
how would i test those ceramic caps without removing them?
ive tried pressing on them and all over the board to replicate the bulb flashing on but nothing seems to work anymore.
so weird how it worked totally fine for almost 24 hours and then nothing

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

i think i did already test all the pins of the transformers and they all are close to each other...nothing stands out
and as for mosfets. i only see 8 pin and 14 pin IC's ... no mosfets

guess ill try that cfl test

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

What is the part numbers on the 8 pin ICs

Can you test again for 24 v at the fuses -

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

the IC's say
4614
B07725

i tested the fuses again and they have 24v on both sides of all fuses

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

i soldered a bit of wire to the end of a 13w cfl bulb that i know does work, and touched the other end of the wire to all the pins on all the transformers with no lighting up at all.

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

The 8 leg IC 4614 is likely to be a mosfet
https://cdn.badcaps-static.com/pdfs/...0e94bf963c.pdf


Tell me you didnt just attach wires to a bulb? you have to cut it open and just
extract the tube without any of the internal electronics.

You attach the wires to the bulb sockets not the transformers.

[vinceroger69]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

not sure if you have saw this selldoor budms new idea
https://www.badcaps.net/forum/showth...x+dx-40l261a12
i persume this is what triplefour is on about?

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

Thanks Vince - no I had not seen that, must have been when I was AWOL - I will have to try it. I thought those bulbs were CFLs not CCFLs ?
EDIT - I see - yes they are just a typo.


Sorry Triplefour your test is a valid one. In that case how about testing the voltage across each of the electrolytics ?

Did you test all the 0 rated resistors yet?

Just the ones AFTER the fuses

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

i did see 24v across all the electrolytics and i tested literally all of the tiny resistors that say 0 on them and they all check out to .3 which is the internal resistance of my dmm ... how do i test the mosfets?

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

Guess they are next in line - use the datasheet and first do this test taken
from retiredcaps 2 seconds to black guide. It is only a quick test for shorts.

Second test With power would be to check the voltages on the pins to see
if they are within the parameters on the datasheet.




Mosfets

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

Note: a shorted mosfet would likely cause a very brief flash of the backlight or no backlight.

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

yay more tests to keep me busy! thank you! will report soon

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms
d) black on pin S2- red on pin G2 - record ohms
e) black on pin S2- red on pin D2 - record ohms
f) black on pin G2- red on pin D2 - record ohms

there are 8 mosfets. starting from the bottom of the inverter board with

Mosfet1
-----------
a) 677
b) 492
c) 1325
d) 733
e) 49k but is slowly rising
f) 1563k climbs slowly to eventually stop here

Mosfet2
-----------
a) 623
b) 492
c) 1277
d) 725
e) 49k but is slowly rising
f) 1563k climbs slowly to eventually stop here

Mosfet 3
-----------
a) 677
b) 484
c) 1324
d) 732
e) 49k but rises slowly
f) 1575k climbs slowly to eventually stop here

Mosfet 4
-----------
a) 623
b) 489
c) 1279
d) 725
e) 49k but rises slowly
f) 1564k climbs slowly to eventually stop here


whew! that was a lot of measurements. before i measure the other half, can someone tell me if im doing something wrong here?
why are the e) measurements rising slowly?
why does the f) measurement rise slowly but eventually stop?
also i found that taking all the measurements from one mosfet and then moving onto the next, i would get different values for e) usually between 40 and 60k though, but all different. when i just went down the row of mosfets and measured each e) thats when i got nearly 49k each time (but it was still slowly rising)
the same sort of effect came with f) measurements. there seems to be much more variance in the measurements if i measure each mosfet entirely and then move onto the next....but if i just take only the f) measurement from each, they seem to line up better.

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

Well those 4 are not shorted - you are putting too much effort into the test
as long as they go above 30 ohms they are likely to be ok.

As to your queries , im sorry I dont realy know, but as you are testing on the board there will be interaction from other components - perhaps budm will comment if he looks in.

[triplefour]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

too much effort? i dont understand. i merely took the measurements you said i should! ill get the other 4 tomorrow

[selldoor]

Re: Samsung LN-T3242H works fine for a day, then wont turn on. intermittent.

Sorry it was a joke, I meant mental effort, as to what the results mean. As you are wanting to learn you are doing it right. Most enquirers just do the tests
post the results and move on the next.