Samsung UA32D4003BM 32" LED NO POWER

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

If you have no current, looks to be another Samsung dead series LED (probably they were using cheap or counterfeit LEDs.) One LED pops, whole lot goes out.

They really f**ked up the D-series models. 55" D6000 and 46" also affected.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

Just want to make sure i got it right, cut the blue wire (pin 1) connect my multimeter to test current, and hook it up in series with the led strip.

how much current am i supposed to get?

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

I would use black wire. I'm guessing blue loop might be for service tech or factory test using a clamp meter, but I'm not sure.

Current, well I'm not sure, but anything more than zero would indicate LEDs not broken.
Realistically, I'd expect around 150~300mA (22~44W LEDs.) Maybe less. What's the power rating of the TV?

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

OK tom, i will cut the black wire tommorow and update it 2:41 AM and i need to go to college tomorrow morning,

just found this ref on the board, any idea what does it say?

about the power of the set, im really not sure it doesnt say,
could be 70watt? sounds a bit low...

[budm]

Re: Samsung UA32D4003BM 32" LED NO POWER

203V@ 165mA, so it seems to me that output voltage is too low since you are only getting 145V, there should be IC for the LED driver circuits that has voltage booster circuit to boost the voltage up to 203V. I would expect the LED driver circuit to go into shutdown if it detects no current flow so I do not expect to see any voltage at the output pin. I need to find the SCH.

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

I would still expect some current flow at 145V but perhaps there is a DC-DC converter which is taking unregulated SMPS voltage and boosting it, fairly common.

[budm]

Re: Samsung UA32D4003BM 32" LED NO POWER

It may not be enough to forward bias the LEDS, an yes most the LED controller IC does use boosted regulator circuit to boosted the b+ up. i think it is related to that MOSFET (it must be part of the boosted circuit driven by the IC) that came off in the pictures in post 1. He needs to get the P/N of that IC next to it.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

so i cutted the black wire (had 12vdc), and connected the multimeter in series to it.
got no current, checked for dc or ac and got nothing. measured on the mili range.

any ideas what to test on next?

(by the way thank you very much for the guidance)

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

What voltage do you measure across the CM852, the 68uF 200V capacitor?

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

I can't find any datasheet for the SEM5025 controller IC, but it is available for sale in the odd place.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

CM852 Got 146Vdc

[budm]

Re: Samsung UA32D4003BM 32" LED NO POWER

It looks like SEM5026

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

had some free time so went and check all elec' for esr and c
one was a bit odd, 8.2uf 400 showed 7.09uf, 3.2ohm,
a little high esr i would say,

about the chip SEM5025 are there any tests possible before ordering it from china and wait for another month?

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

It looks like SEM5026

It did initially to me, but if you compare package of SEM5026 and SEM5025 the SEM5025 is the right one.

had some free time so went and check all elec' for esr and c
one was a bit odd, 8.2uf 400 showed 7.09uf, 3.2ohm,
a little high esr i would say,

That's OK for a cap that size.

about the chip SEM5025 are there any tests possible before ordering it from china and wait for another month?

Yes, do you have an oscilloscope available? Or one you can borrow?

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

i have one at college, but i can't bring the whole tv with me there,
but the psu is small so it won't be a problem.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

what about the STR W6053S whould i replace it too?

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

If you have proper output from the PSU's other rails, I don't see any need to replace that IC.

With the scope you can check the GATE and DRAIN pin waveform at the FET. Also cheeck the GATE node with the FET removed and installed.

Two possibilities:
- Gate waveform available, good amplitude (0~10V ideally), duty cycle >10% but output still low - bad output diode, or shorted turn in inductor.
- Gate waveform weak or not present, when FET removed this does not change, IC is probably bad.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

The FET you are refering to, is it the one i replaced? MDD5N40?

i think i tested 127 volts on it, i don't think our scope at college can take it, hehe

[tom66]

Re: Samsung UA32D4003BM 32" LED NO POWER

Q9101.

Use a 10X probe and you will be OK.

[s_henya]

Re: Samsung UA32D4003BM 32" LED NO POWER

maybe resoldering the caps changed something i managed to get 200vdc on the bluse wire sooner it was 140, and on the black got 60vdc,

i sounds like its want to start but the fails,

and now i have 3 blinks,

is it possible that i have a bad connection problem or bad control board,
its a touch panel not the usual buttons.