Samsung LE32R86BDX No Backlight

[Electronic91]

Hi everyone,

I'm sorry for my bad english

This thread about a Samsung LE32R86BDX with a PSU BN44-00155A & an Inverter Board INV32N12A Drived by a SEM2006
I recovered this LCD with severals problems.
At first the TV was'nt turning on at all, no red light. I found the RM801 0.22 ohms resistor cut and after changing it
the red light going on and the TV turning on when touching the front panel......but there is no backlight at all (no flash & I don't know at this time if there is picture).

Measure on the PSU are the following :

5v -> 5v
12v -> 12v
13V -> 12.1V (??)
24v -> 24v



Measure on the Inverter Board :

Transformers Secondaries -> 1250/1275 ohms (expected 1250 ohms)
Little transformer T3 Primary and Secondary -> 36 ohms (expected 40 ohms)
Fuse F1 is OK (24v on the two pins)

So for the following tests I disconnect the Main Board and forced the PS_on to 5v and the same thing for BL O/F
I took the mesure on the pins of the SEM2006 IC:

Pin / Symbol / Measure
1 VREF 4.8v
2 SDT 0v
3 S/S 2.1v
4 HF 1.1v
5 DET 0v
6 ARC_P 0v
7 ARC_N 3.2v
8 FB 3.5v
9 ERO 0.5v
10 OVP 0v
11 PGND 0v
12 N1 0v
13 N2 0v
14 VCC 24v
15 UVLO 4.8v
16 EN 3.5v
17 FAIL 0.8v
18 SGND 0v
19 CT 2v
20 RT 2v
21 HRT 5v
22 BRT 1.5v
23 BCT 2v
24 BDIM 0v

When I was tooking measure around the pins 8 & 9 the Backlight start for a second, I thing I did a short circuit with my probe....

So I need some help there because I don't know how to interprate my results, I just understand that the two Channel MOSFET Driver output pins (N1 & N2) are low but I don't know why.

If you have and idea of what can I test know, it would be great

Thanks

[dick_barton]

Re: Samsung LE32R86BDX No Backlight

Test Q101,2,3 and 4

[Electronic91]

Re: Samsung LE32R86BDX No Backlight

Thanks Dick_barton

So desolder the 4 chips and measure them in diode mode ?

[dick_barton]

Re: Samsung LE32R86BDX No Backlight

They tend to go short when faulty so you can measure them in diode mode while still on the board. If they are short then replace them.

[Electronic91]

Re: Samsung LE32R86BDX No Backlight

the measures are the same on Q101,2,3 and 4, no one is short.

[Electronic91]

Re: Samsung LE32R86BDX No Backlight

Here some better pics of the inverter board INV32N12A - HS320WV12

The transformers are LT-312 (TMP 0713AD), if someone know the value of primary for this kind of transformers.

Thanks

[Andrew F. Ali]

Re: Samsung LE32R86BDX No Backlight

You can test and compare the primaries for each of the transformers. They should be pretty close. The secondaries for each of the transformers should be close also in DCR readings.

[Electronic91]

Re: Samsung LE32R86BDX No Backlight

This is what I did and found around 0.5 ohm, so I was suspicious but it seems to be ok.

For the secondaries I found the value in the SEM2006 Datasheet (1.25 Kohms) so every transformers is good according my measure.

Thanks

[vinceroger69]

Re: Samsung LE32R86BDX No Backlight

This maybe a failed ccfl/eefl tube inside the lcd panel

[Electronic91]

Re: Samsung LE32R86BDX No Backlight

Thanks Vinceroger69
But without ccfl tester or a knew good inverter board I'm stuck.....hum