Samsung Syncmaster 940BW

[saintlouis74]

My Syncmaster was having trouble starting same times take 5-10mins to come on, then one day i turn it off and it wouldnt come back on.. So I immediately thought it was a blown and i took it off and it sure was.. So i replaced those caps still wasnt getting any power or blue Led..

i think the power supply is good, but im still new so im not sure

CN201

2.86
15.05
GRD
GRD
GRD
5.14
5.14
0.13
0.13

and on the Main board all test points on back in white box are the right voltage expect for one on the front

CN400

Pin 1 should be at +5v (says the marking on the board) but getting 0.01

anyone point me in the right direction.. would like to learn and fix it instead of buying the board

[saintlouis74]

Re: Samsung Syncmaster 940BW

does all 3 of these test points suppose to measure 5v?

[budm]

Re: Samsung Syncmaster 940BW

CN201

2.86 (B-DIM)PWM Dimming signal
15.05 (+13V) un-regulated (also used for the backlights inverter circuit, and since the backlights are not on the voltage is high)
GRD
GRD
GRD
5.14 (+5V)
5.14 (+5V)
0.13 (A-DIM, Analog dimming)
0.13 (O/F) for backlights on-off signal to the inverter circuit, >2V = ON, <1V = OFF).
So your power supply is OK.
CN400 +5V is the switched 5V for feeding the T-CON board on the LCD panel assembly, in standby mode = 0V, when monitor is turn on and PC signal is present, then it will be turn on and supply 5V to the T-CON.
The question is, before replacing the caps, you were at least be able to turn it on with several tries, but now after the caps replacement, you are no longer even get the power LED to come on. If that is the case, then I would the inspect your works very closely and any wires an connections.

[saintlouis74]

Re: Samsung Syncmaster 940BW

The question is, before replacing the caps, you were at least be able to turn it on with several tries, but now after the caps replacement, you are no longer even get the power LED to come on. If that is the case, then I would the inspect your works very closely and any wires an connections.

Before replacing the caps i couldnt get it to turn on after pressing it 100 times, tried for 3 or 4 days, before replacing the cap... so before replacing the caps no power on or power LED and after the same problems

i went over my work and tested everything i could find 3 times... and if PS is good, i never touched the Main board.. idk

[Davi.p]

Re: Samsung Syncmaster 940BW

But since the pwr board works and i think he don't have replaced smd caps on main board the problem is more difficult i guess.. maybe a regulators check on main bd will be one of the next steps.. then a mainb. recap if none..

[budm]

Re: Samsung Syncmaster 940BW

I am not sure how close the SCH to your chassis/model version.
You can download the service manuals:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[saintlouis74]

Re: Samsung Syncmaster 940BW

I am not sure how close the SCH to your chassis/model version.
You can download the service manuals:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

SAMSUNG 940BW-PLUS CHASSIS LS19HAK SM

i did the troubleshooting for No Power and everything matched up perfect

[saintlouis74]

Re: Samsung Syncmaster 940BW

But since the pwr board works and i think he don't have replaced smd caps on main board the problem is more difficult i guess.. maybe a regulators check on main bd will be one of the next steps.. then a mainb. recap if none..

gonna do a recap right now. already have some smd for it..ill let you know

[saintlouis74]

Re: Samsung Syncmaster 940BW

But since the pwr board works and i think he don't have replaced smd caps on main board the problem is more difficult i guess.. maybe a regulators check on main bd will be one of the next steps.. then a mainb. recap if none..

did a recap on main and still no power

[Davi.p]

Re: Samsung Syncmaster 940BW

but the regulators check? Place the - terminal of dmm around the screw hole, then report each of the 3 pins of the reg. IC601 IC602, then with power off check in diode mode D600 D603, i don't think that you will find the culprit in theese but give a try..

[selldoor]

Re: Samsung Syncmaster 940BW

did a recap on main and still no power

What exactly do you mean by NO Power?

No Picture?
No Back Light?
No Power LED?

None of the above

[saintlouis74]

Re: Samsung Syncmaster 940BW

What exactly do you mean by NO Power?

No Picture?
No Back Light?
No Power LED?

None of the above

no picture, no backlight, no led... put still getting all correcting reading from PS

[saintlouis74]

Re: Samsung Syncmaster 940BW

but the regulators check? Place the - terminal of dmm around the screw hole, then report each of the 3 pins of the reg. Ic601 ic602, then with power off check in diode mode d600 d603, i don't think that you will find the culprit in theese but give a try..

ic601

1. 3.75
2. 1.80
3. 0
tab. 1.80

ic602

1. 5.14
2. 3.3
3. 0
tab. 3.3

d600

4.45
5.14

d603

4.45
3.76

[Davi.p]

Re: Samsung Syncmaster 940BW

regulators are good sorry, i think you have a software issue and is too hard to repair for me, as a desperate attempt try to access the factory menu by from off state keep pressed 2 of the keys then press power, another try can be hook the mon. to a pc and see if it recongnizes, then start a search for a sw to update firmware through vga cable, i don't know if it has some sense, try to reset the user setting by shortcircuiting some pins, (tell me all the p/n of the 8pin ICs), last try to find a replacement mainboard.

[selldoor]

Re: Samsung Syncmaster 940BW

Can you test the Diodes with the leads reversed as well.

The VRs are probably ok but as you have not told us the part numbers
cannot be certain.

Do the back lights not flash at all?

[saintlouis74]

Re: Samsung Syncmaster 940BW

CN201

2.86 (B-DIM)PWM Dimming signal
15.05 (+13V) un-regulated (also used for the backlights inverter circuit, and since the backlights are not on the voltage is high)
GRD
GRD
GRD
5.14 (+5V)
5.14 (+5V)
0.13 (A-DIM, Analog dimming)
0.13 (O/F) for backlights on-off signal to the inverter circuit, >2V = ON, <1V = OFF)

O/F for backlight on-off Signal says in Troubleshooting of the manual should read 5v.. and its only reading .13v.. solution says to Replace IP Board soo..

[Davi.p]

Re: Samsung Syncmaster 940BW

i don't have read the service m. but ON-OFF is an input signal for the IP board (Inverter-PSU board) so if it is low the culp is on the main board.

[saintlouis74]

Re: Samsung Syncmaster 940BW

i don't have read the service m. but ON-OFF is an input signal for the IP board (Inverter-PSU board) so if it is low the culp is on the main board.

[Davi.p]

Re: Samsung Syncmaster 940BW

i dont need the srv man, every on-off act the same way..

[lexwalker]

Re: Samsung Syncmaster 940BW

My Syncmaster was having trouble starting same times take 5-10mins to come on, then one day i turn it off and it wouldnt come back on.. So I immediately thought it was a blown and i took it off and it sure was.. So i replaced those caps still wasnt getting any power or blue Led..

i think the power supply is good, but im still new so im not sure

CN201

2.86
15.05
GRD
GRD
GRD
5.14
5.14
0.13
0.13

and on the Main board all test points on back in white box are the right voltage expect for one on the front

CN400

Pin 1 should be at +5v (says the marking on the board) but getting 0.01

anyone point me in the right direction.. would like to learn and fix it instead of buying the board

Before replacing the caps i couldnt get it to turn on after pressing it 100 times, tried for 3 or 4 days, before replacing the cap... so before replacing the caps no power on or power LED and after the same problems

i went over my work and tested everything i could find 3 times... and if PS is good, i never touched the Main board.. idk

Looking at those capacitor markings and colors, what were the replacement capacitor brand(s) you've used? Have you tried replacing the big filter/smoothing 100uF 450V capacitor?