Samsung LN-T2353H won't turn on

[tibimakai]

I have picked up this small TV which won't turn on.
The LED is on, which means that there is a STBY voltage.
If I keep pressing a couple of times the touch buttons, eventually the LED will turn off and the Samsung logo will blink a bit, but nothing happens with the screen.Then the LED will turn back on.
I have opened it up, no obvious bulging capacitors.
It's very familiar power supply, I think it's very similar to the 245 or 226, not sure which one.
It has those three 76 OHm resistors next to each other it has the F9222L chip.
Some of the voltages are missing.
I don't have the 24V, 9V and 12V.
The PS-ON is high, at 4.12V, 5.3V is there and the STBY 5V as well.
387V is there as well.
I'm not sure what should I be doing next, replace all the capacitors?

[tom66]

Re: Samsung LN-T2353H won't turn on

No, shot-gun replacing caps at this point is unlikely to fix the problem.
You have high PS-ON but have you checked what it is in standby? i.e. does it change when pressed?

[tibimakai]

Re: Samsung LN-T2353H won't turn on

The high PS_ON is in standby.
When eventually it changes states, drops to 0V and then back up to 4.18V. After that I can hear a slight click(sounds like is coming from the bottom ccfl) and the light at the bottom of the TV blinks for a second.
I have forgot to check the 24V and the rest of 12V and 9V.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

I have checked them and they don't change at all.
What else I have noticed, that actually I haven't switched on the TV myself, it was doing it by itself.
It seems, like it is in a start up and shut down loop mode. I can hear some slight whistle like noise, most likely some high voltage makes that sound.

[tom66]

Re: Samsung LN-T2353H won't turn on

When PSON goes low, monitor the PSU outputs. A second meter may be handy here, or you can synchronise your measurement with the click sound.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

I have checked those outputs the same way as the PS_ON and there outputs did not change.
Basically, I have to hold the meter's probes on each output and wait until it starts by itself.
I have another meter if it's needed.

[tom66]

Re: Samsung LN-T2353H won't turn on

You can stick the black probes in the metal chassis parts, then red probe on PSON, and another red probe on B13V, and see what happens.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

No change.
I have removed the PS_ON wire from the connector and it still does it.
That is weird.
The PS_ON voltage goes back to 5.2V when it's unplugged, but it turns on and off this one too.

[tom66]

Re: Samsung LN-T2353H won't turn on

Still does -what-?

[tibimakai]

Re: Samsung LN-T2353H won't turn on

Turning on and off by itself.

[tom66]

Re: Samsung LN-T2353H won't turn on

That may be normal, perhaps it is entering protect mode.
You need to test all the outputs, if they are dead, test all output diodes.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

Diodes check out OK, at least the three pin ones.
It must be something common to all the voltages and that has to be in the primary side. I may have noticed something.
Check out the circled parts, the resistor has a blown side and the blue capacitor shows 0.9 Ohm.
These two components feed the transformer.
If I remember, one of these 245 or 226 monitors suffered of some 18 nF capacitor no?

[tom66]

Re: Samsung LN-T2353H won't turn on

If the cap shorted it's quite understandable for that resistor to open. It is quite/very rare for those caps to fail short though.

Unfortunately, I don't (yet?) have a schematic of this PSU... but Elektrotanya looks to have one.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

Tom, what do you think about the IC, it could be damaged too?

[budm]

Re: Samsung LN-T2353H won't turn on

I believe that is the fusible resistor for the B+ for feeding the switching power supply section of that big power transformer..

[tibimakai]

Re: Samsung LN-T2353H won't turn on

These bad components are 0.22 Ohm 1W fusible resistor and the capacitor is 0.018 uf/630V capacitor?
I had some 0.1 Ohm/2W resistors and put them in series and I had a 0.018uf capacitor and I gave it a try.
I haven't measured anything, but at least one of the resistors blew up.

[budm]

Re: Samsung LN-T2353H won't turn on

The cap is actually shorted out? The cap is part of the Bridge drive circuit for that transformer,it is for the DC blocking. The FLAT PACK MOSFET module may be shorted out, you can check the resistance between S and D pins.
Remove the cap and check the resistance on those two pad of the removed cap, more likely that it will still show shorted circuit.
Check the resistance between PIN 23 and PIN 19 (MOSFET 2), PIN 19 and PIN 4 (MOSFET 1) of that Flat pack module for short.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

I have tested in circuit only and it showed 0.9 Ohm.
The resistors that I have soldered in in series were fusibles also.
Most likely the F9222L has a short if it blew the resistor. I may still have one of these ICs from a previous repair.
I will check it out tomorrow.
Bud if I understand the codes, I need a 0.22 OHM 1W fusible resister and a 0.018 UF/630 V capacitor, right?
I wold like to place a Digikey order for these parts and that MUR360 diode.

[budm]

Re: Samsung LN-T2353H won't turn on

Yes. I doubt that the cap shorted out, very rare for it to happen, if it is bad, get higher voltage rating if you can.

[tibimakai]

Re: Samsung LN-T2353H won't turn on

You were right about everything, as usual.
F9222L shorted, cap it was good(at the pads was showing 0.2 Ohm with cap removed).
I have replaced the IC and put back the original cap and waiting for the resistor to arrive on Monday.