samsung 206bw replaced transformer

[Mark369]

I got this monitor and replaced all cap. all was good
for i say 8 months then i would get a power light and 1sec. to back light.

i tested all caps with blue esr meter and are good.
found transformer to be bad? part number 8tcoo327

it is a 8 pin transformer two at ether end and two close to center on ether side on two end pins(1 and 2) i get with my meter is on 2k setting 1.07 on other set of end pins (7 and 8) i get no reading at all. across center sets of pins i get 0.001 (3 and 4) and 0.000 (5 and 6).

on new transformer i get 6.51 and 6.52 the center pins i get 0.001
all with 2k setting.

so i replaced the transformer now i don't get any backlight at all but i have a blue power light. just like if the monitor was working right.

so i check the volts at the on pin and see it go to 2v then down to 0.002v

checked power to video board and found 3v 13v.

just don't know what to do now i have most of tools that i need 15Mhz scope DMM, ESR Meter. just not your guys smarts, yet. thanks for your time.

[alexanna]

Re: samsung 206bw replaced transformer

Would you take some pitcures of the 1st and 4th photos again,do not use a flash and try to get them in focus.We need to be able to read the printing on the boards

[Rtech]

Re: samsung 206bw replaced transformer

Why do you read 6.51 and 6.52 on the transformer,I ask myself ??? that would indicate to me ohms !!!!. what does your meter read if you measure a 1K(1000 ohms)resistor ???

[Mark369]

Re: samsung 206bw replaced transformer

tested my meter with a 82 ohms 1% resistor with blue esr meter and dmm and got 82.1
so i think that it is working right. well try to get better photos soon not to bright around here for the last week.

[Mark369]

Re: samsung 206bw replaced transformer

the lcd controller ic is oz694gn.

any one know if pin 3 has to stay at 2v to stay on. if it does what in the controller board
would cause on pin to go low

[Mark369]

Re: samsung 206bw replaced transformer

just hooked every thing up to do some measurments and the controller board started smoking. I guss i was right to think that some thing was up with the board giving 2v then 0v on on/off pin now need to find out what was smoking

[Rtech]

Re: samsung 206bw replaced transformer

Why do you read 6.51 and 6.52 on the transformer,I ask myself ??? that would indicate to me ohms !!!!. what does your meter read if you measure a 1K(1000 ohms)resistor ???

From that then..the 6.51 and 6.52 you measured on the transformer must be ohms ??????,and therefore cannot be correct, as you should be looking for 400-1100 ohms.

[Rtech]

Re: samsung 206bw replaced transformer

tested my meter with a 82 ohms 1% resistor with blue esr meter and dmm and got 82.1
so i think that it is working right. well try to get better photos soon not to bright around here for the last week.

.
From this result then, the 6.51 and 6,52 you measured on the transformer,must be ohms ????/and as you are looking for between 400-1100 ohms across the secondaries,then this would indicate something definitely wrong,and may be the reason why you got smoke !!!

[Mark369]

Re: samsung 206bw replaced transformer

I just seen I did not mean to put 6.51 sorry.
the readings I get are 0.651 and 0.652.
What would that have with the video board not sending on high 2v and keeping it there.

And what would be smoking on the video board

[Rtech]

Re: samsung 206bw replaced transformer

Then should the meter not read 651.0 and 652.0.that would then be 651ohms ???
Once you sre sure about the transformer readings, then I would plug the lamps into the board,put mains onto the board(NOTE:this is on the Power supply/Inverter board)WITH NO other boards connected,apply 3volts DC(2 x 1.5 batteries in series),between the Backlight ON/OFF connection,on the connector that comes from the Logic Board and a Ground point.and then the lamps should light IF all is well with that board.

[Mark369]

Re: samsung 206bw replaced transformer

Thank you for your reply i am very busy at work lately and will try when i get a min.
the meter was on the 2k setting, so that would be 651.00ohms and 652.00ohms, as my meter only has 200ohms, 2k, 20k, 200k and 2M. that would mean that at the 200ohm setting i don't get a reading but would get 651ohms on 2k setting i hope this clears it up.

[Mark369]

Re: samsung 206bw replaced transformer

up date i have put 3v in to the invert on pin and the back lights turned on.
so i know that the transformer was bad and replaced it. now some thing on the video board was smoking i think it was one of the button style resistors but the pcb marking starts with Lxxx?

[Rtech]

Re: samsung 206bw replaced transformer

up date i have put 3v in to the invert on pin and the back lights turned on.
so i know that the transformer was bad and replaced it. now some thing on the video board was smoking i think it was one of the button style resistors but the pcb marking starts with Lxxx?

The letter 'L' indicates it is an Inductor(coil)

[Mark369]

Re: samsung 206bw replaced transformer

Yes I know L indicates it is an Inductor. on top it says 0.22 and when i measure it i get 0.001 on the 2k setting. so i think it is ok. what do you guys think i should check next.

[Mark369]

Re: samsung 206bw replaced transformer

I found the part that was smoking it is a Mosfet at IC 706 FDS9933A and found service manual.
My logic board is BN41-00807A the schematic say that the Mosfet is a FDS9933A, pg 46.
and on R742 im getting 257ohms schematics say it should be 100ohms and i think that i read 104 on face of it. maybe this is why it shorted.

i was thinking of using this Mosfet as replacement.

Do you guys think that it would work? I have ordered it and hoping to get it tommaro. and do you have any thoughts on what eles might be bad, what would make the Mosfet short.

the readings im getting between the gate and source is 0.265 on the 2k setting.

Thank you all so very much. I have been learing so much from you guys over the last year, when i stared my new hobby.

[Rtech]

Re: samsung 206bw replaced transformer

I found the part that was smoking it is a Mosfet at IC 706 FDS9933A and found service manual.
My logic board is BN41-00807A the schematic say that the Mosfet is a FDS9933A, pg 46.
and on R742 im getting 257ohms schematics say it should be 100ohms and i think that i read 104 on face of it. maybe this is why it shorted.

i was thinking of using this Mosfet as replacement.

Do you guys think that it would work? I have ordered it and hoping to get it tommaro. and do you have any thoughts on what eles might be bad, what would make the Mosfet short.

the readings im getting between the gate and source is 0.265 on the 2k setting.

Thank you all so very much. I have been learing so much from you guys over the last year, when i stared my new hobby.

The resistance between gate and source should be more than 30ohms.R742 you refer to, 104 on it means 100Kohms,and if it is, then to be sure you know what value it is, you may well have to measure it OUT of circuit. Most mosefets have a very low value resistor somewhere around it, so would check all of those,and any diodes,before replacing any Mosfet.

[Mark369]

Re: samsung 206bw replaced transformer

yes your right i miss read it, it is 100kohms.
acording to the schematics there is no diodes connected to this part.

still did know if the part that i ordered is a good replacement and if the R742

well i the replacement Mosfet must be good because im using the monitor now is all working ok for now

[Mark369]

Re: samsung 206bw replaced transformer

oh yea i replaced the 100kohms resistor too it was so small.

used a heat gun and a surface mount cap popped right off the board didn't have a replacement. but every thing is still working good.

Thank you Rtech.

[Mark369]

Re: samsung 206bw replaced transformer

just a thought do you think i could have put ribbon cable in the pannel upsidedown and shorted the mosfet after i put the new high output transformer in?

[Rtech]

Re: samsung 206bw replaced transformer

We have all made silly mistakes at some time,and I have certainly done that, and then my tears helped to put the flames out.Well done for the repair.