Samsung LE32D450GW1 as lightsword

[Prosatanosz]

HI!

Have you ever seen that? Semi-illuminated fluorescent lamp. There was a short circuit of high fat low fat, besides several semiconductors and low-value resistors broke. I couldn't find any other error.

FDPF5N50NZU replaced with STD4NK60ZT4
KDS184 replaced with 2x1N4148
2N7002K replaced with 2N7002

Low fat voltage 195V= as printed on board
High fat voltage 200V= or 10V~ measured with multimeter, not a scope (printed 280V~)

Inverter: INV32T4UB REV 0.1 2 pcs transformer 2x2 ccfl coil
Display: T315XW03 V.D

There is 4 u shaped ccfls seems good condition.

What is wrong? Low high voltage? How much should it be?

[budm]

Re: Samsung LE32D450GW1 as lightsword

Can we see the pictures of the inverter transformer board?
BTW, the High and LOW fet output are high frequency AC around 50 ~ 80KHz so your AC meter will not be reading it correctly.

[Prosatanosz]

Re: Samsung LE32D450GW1 as lightsword

Hi budm!

This is the inverter.

Yes we need a scope to measure h fet voltage. Cca seems ok, because L voltage depends on h voltage. L volt is 195V= exactly as we need.

[budm]

Re: Samsung LE32D450GW1 as lightsword

That power supply board had Inverter transformer primary winding driver circuit as shown in the schematic, the LOW (FET) is the return line to GND via CI826.
The primary winding of the two inverter transformers are connected in series one end of the series connection is connected to the HIGH (FET), the other end of the series connection is connected to the LOW (FET) which then return to circuit GND via CI826. I am very surprised that you are able to read 195VAC on the LOW (FET), but since the lamps are lit up that means the HIGH (FET) Volatge must be present and must be higher than 195VAC. Right now it looks like the Lamp are not getting enough high Voltage to drive it fully on.
Do you have about 380 ~ 400DVC measured right between the two legs of the main filter cap in the hot side? Check the capacitance of that DC Blocker/coupling cap CI826 to see if it is still around 470nF or not.

[Prosatanosz]

Re: Samsung LE32D450GW1 as lightsword

CI826 is 470n as we expected. PFC_OUT is 385V. Today the situation is worse, the tubes shining on shorter sections. The difference is less between H and L output measured with multimeter.

SEM2106 pins:

1 vref: 4.95V
2 std: 0V
5 det: 0V
6 arc_p: 0v
7 arc_n: 3.25V
8 fb: 2.27V
9ero: 0.81V
10 ovp: 0V
15 uvlo: 4,82V
16 en: 4.95V
17 fail: 0V
12,13 N1,N2: 0.6V

[Prosatanosz]

Re: Samsung LE32D450GW1 as lightsword

Victory! Replace the caps on sem2106 pin 2,3,4. Well done.