Samsung Syncmaster 943B problem

[falcontech]

Hello
I have a problem with a samsung 943B, initially thinking it was a power problem i replaced the power board which is a bn44-00082e, i had a flashing of the ccfl lamps and the monitor would not start, i replaced the power board and the problem is remained, thinking they were the lamps I tested them with a ccfl lamp tester and they are all working, at this point I think it is the main board which is a BN41-01172B, my question is, before making a further purchase there is a way to turn on the lamps without the main board to exclude that the new power board is also broken? Of course without the main board the lamps show no signs of life, so maybe I should short out two of the 12 output pins to turn on the lamps, like the guy on youtube did Grazie

https://www.youtube.com/watch?v=fia_pXizejY&t=46s

[momaka]

Re: Samsung Syncmaster 943B problem

there is a way to turn on the lamps without the main board to exclude that the new power board is also broken?

Yes, you can test the inverter with the main board disconnected.

My guess would be that pin 8 (O/F) on the power supply board is for the inverter On/Off control pin. Pulling this pin up to 5V (so connect pins 5 or 6 to pin 8) should turn on the inverter (and backlights.) Probably best to use a 100-Ohm series resistor between these two rather than a direct connection, though... just in case.
Pin 1 (ADJ) should just be for adjusting the backlight brightness, but usually that can be left unconnected for testing.
I'm not sure what pin 7 (DCR) is for, but you can probably leave that one alone as well.
So connect pins 8 to 5/6, and see if your backlights turn ON and stay ON. They should stay ON as long as pin 8 is connected to pin 5/6.

Also, I'm linking your thread here with the power supply, so that people can see the inverter you're dealing with.
https://www.badcaps.net/forum/showthread.php?t=99034

[falcontech]

Re: Samsung Syncmaster 943B problem

Yes, you can test the inverter with the main board disconnected.

My guess would be that pin 8 (O/F) on the power supply board is for the inverter On/Off control pin. Pulling this pin up to 5V (so connect pins 5 or 6 to pin 8) should turn on the inverter (and backlights.) Probably best to use a 100-Ohm series resistor between these two rather than a direct connection, though... just in case.
Pin 1 (ADJ) should just be for adjusting the backlight brightness, but usually that can be left unconnected for testing.
I'm not sure what pin 7 (DCR) is for, but you can probably leave that one alone as well.
So connect pins 8 to 5/6, and see if your backlights turn ON and stay ON. They should stay ON as long as pin 8 is connected to pin 5/6.

Also, I'm linking your thread here with the power supply, so that people can see the inverter you're dealing with.
https://www.badcaps.net/forum/showthread.php?t=99034

No, this doesn't work, I realized that with the main board connected the last two pins k1 and k2 receive respectively 14, xx volts and 5.1 volts I don't know if it can be useful

[R_J]

Re: Samsung Syncmaster 943B problem

K1 & K2 are from the button board, Key1 Key2 should only have about 3.5 volts not 14v. k1&k2 connect to CN5 where the buttons connect

[falcontech]

Re: Samsung Syncmaster 943B problem

I check again with the connector of the connected commands and I tell you

[falcontech]

Re: Samsung Syncmaster 943B problem

K1 & K2 are from the button board, Key1 Key2 should only have about 3.5 volts not 14v. k1&k2 connect to CN5 where the buttons connect

ok I rectify, on k1 and k2 I have 1.80 volts, on pin 8 I have only 3.10 volts, if they must be 5.1 I think they are insufficient

[R_J]

Re: Samsung Syncmaster 943B problem

ok I rectify, on k1 and k2 I have 1.80 volts, on pin 8 I have only 3.10 volts, if they must be 5.1 I think they are insufficient

The control voltages from the main board are 0~3.3v

[falcontech]

Re: Samsung Syncmaster 943B problem

The control voltages from the main board are 0~3.3v

what do you advise me to do to make this inverter turn on?

[R_J]

Re: Samsung Syncmaster 943B problem

Disconnect the main board from the power supply so you don't damage the main board, Then use about a 1kΩ resistor between the +5.1 volts and O/F that should turn on the backlights, if it does not, then connect another 1kΩ resistor between +5.1V and ADJ
I think the DCR pin is used on this power supply

[falcontech]

Re: Samsung Syncmaster 943B problem

Disconnect the main board from the power supply so you don't damage the main board, Then use about a 1kΩ resistor between the +5.1 volts and O/F that should turn on the backlights, if it does not, then connect another 1kΩ resistor between +5.1V and ADJ
I think the DCR pin is used on this power supply

all clear, except that I did not understand what to do with the dcr pin

[R_J]

Re: Samsung Syncmaster 943B problem

for the DCR pin, Look at the back of the board where the plug is located, I do not think that the DCR pin is connected to any circuit.

[lotas]

Re: Samsung Syncmaster 943B problem

Wiring Diagram - Main Board

[falcontech]

Re: Samsung Syncmaster 943B problem

for the DCR pin, Look at the back of the board where the plug is located, I do not think that the DCR pin is connected to any circuit.

Yessss ... they turned on, so the power supply is ok ... now I should figure out what's wrong with the motherboard, assuming it's repairable ...

[falcontech]

Re: Samsung Syncmaster 943B problem

any idea to understand what could be in the main?

[R_J]

Re: Samsung Syncmaster 943B problem

You could disconnect the flat cable between the main board and the panel to see if the power supply and backlights turn on, as there may be a fault with the panel.

[falcontech]

Re: Samsung Syncmaster 943B problem

You could disconnect the flat cable between the main board and the panel to see if the power supply and backlights turn on, as there may be a fault with the panel.

all the tests done so far have been done just as you advised me, without flat on main or panel

[falcontech]

Re: Samsung Syncmaster 943B problem

You could disconnect the flat cable between the main board and the panel to see if the power supply and backlights turn on, as there may be a fault with the panel.

I did some tests on the main, all the voltages are ok, except for pin 8 which theoretically should receive 3.3 volts but only 3.10 arrive, based on the lotas scheme what could I control?

[R_J]

Re: Samsung Syncmaster 943B problem

pin8 is o/f which is a control line to turn the power supply on and off 3.1 volts is fine. 0.2 volts is not going to make a difference.

[falcontech]

Re: Samsung Syncmaster 943B problem

pin8 is o/f which is a control line to turn the power supply on and off 3.1 volts is fine. 0.2 volts is not going to make a difference.

do you say to replace main directly or is there something I could check?

[R_J]

Re: Samsung Syncmaster 943B problem

do you say to replace main directly or is there something I could check?

As you can see there is not much to the main board, if the regulators are ok, it may be a firmware issue? but I think the boards are quite cheap to replace.