Samsung Syncmaster

[mojo_tsi]

Hi there,

i am currently fiddling with a samsung monitor/tv combo.

Backlight cuts out after about a second, picture seems fine otherwise.

1. I touched up some suspect solder joints especially at D109 wich seemed to be quite toasty give the color of the PCB

2.Tested some caps in circuit and desoldered some but ballpark numbers seemed okay(device used was the M-Tester)

3.Measured resistance on the inverter transformer, very low ohm on the primary and about 1.3k ohm on the secondaries.

4. No idea what to do know, probably measure voltages on the live board, wich i kinda wanted to avoid...also i got no spare CCFL..

[R_J]

Re: Samsung Syncmaster

Can you hold the back of the tv up to your monitor so we can read the model number?
Or just post it.
Try disconnecting one of the ccfl plugs, does the backlight come on for a second, if yes, recoonect it and disconnect the other one, that should tell you if the ccfl is ok (but could still be bad)

What is the BN44-????? number on the board and also the ccfl drive ic number if you can read it

[mojo_tsi]

Re: Samsung Syncmaster

I thought i had the model in the thread title.

Model: P2770HD Type No.: EM27TS
Model Code: LS27EMDKU/EN

There is a Top and a Bottom CCFL assembly, each containing 2(?) Lamps
The CCFL's both shut down after 1s no matter wich one assembly i disconnected, so no new information there.

The PSU-Board BN from the service manual i found online is BN44-00322A, found a pic of a spare board for sale that also had the discoloration around D109 so i think the BN number is correct.

[mojo_tsi]

Re: Samsung Syncmaster

IC wise i found three on the underside of the power PCB.

Biggest one reads: SEM2105 1026

[mojo_tsi]

Re: Samsung Syncmaster

Just measured the voltages on the low voltage side(main board) 5V rails where at about 5.1V, 14.5V was only at 13.28V.

Maybe this is another P2770HD where the TM-09210 died?

The coil resistance was okay, and there where no discolorations but i guess i'll order the transformer and try.

[R_J]

Re: Samsung Syncmaster

I checked the other threads and one said they measured the 14.5 as 13.?? so its likely normal. The only other schematic I found that used the sem2105 was for a BN44-00251D.
Seems theTN-09210 fixes a lot of the backlight problems so it could be bad, one shorted turn is all it takes and that will not change the dc resistance at all

[mojo_tsi]

Re: Samsung Syncmaster

Fixed it, thank you!

The voltage stayed at 13.x, even with new caps and an new TM-09210.

The new TM-09210 had about 986 Ohms resistance on the secondary instead of 1.4k but the backlight is back so i wont complain.

Since i switched the caps & the TM at the same time i cant be 100%, but i'd guess the TM was bad.

[Andrew F. Ali]

Re: Samsung Syncmaster

I would tend to think the TM-09210 was the problem.