Samsung SyncMaster B1940

[tama4tama]

Dear friends,
I have this Samsung SyncMaster B1940 LCD monitor which is died , the user said he was using it and then went off. I have check the fuse and others things all look fine.
Please help me on this one?
Thanks.

tama4tama

[alexanna]

Re: Samsung SyncMaster B1940

Dear friends,
I have this Samsung SyncMaster B1940 LCD monitor which is died , the user said he was using it and then went off. I have check the fuse and others things all look fine.
Please help me on this one?
Thanks.

tama4tama

A more detailed description of your problem would be helpful.
When you hook up the monitor to a computer can you turn on and off the monitor with the front power switch?
Do you see any indication of the backlights trying to turn on?

[tama4tama]

Re: Samsung SyncMaster B1940

As the user said it was working and went off, I hook to computer but still the same, there is no back light when turn on because there is no light on the front.

[PlainBill]

Re: Samsung SyncMaster B1940

As the user said it was working and went off, I hook to computer but still the same, there is no back light when turn on because there is no light on the front.

Thank you for the pictures. They make helping you very easy. In the first picture the connector for the cable to the signal card is in the lower right corner. Just to the left of that is the identification for every pin on that connector.

The following test will be done with power on, potentially lethal voltages are present, so be careful. With AC power connected to the power supply, but the signal card disconnected, measure the voltage from any of the pins labeled GND to the pins labeled B-Dim, +13V, +5.1V, and O/F.

Now, unplug the power cord, reconnect the cable to the signal card, reconnect to AC power, and check the same points again.

Now, I would like a small favor. What is the part number of IC801S?

PlainBill

[tama4tama]

Re: Samsung SyncMaster B1940

Without the signal card connected
Pin 1 B-Dim= 0.00
Pin 2 13V= 12.96V
Pin 3 GND=
Pin 4 GND=
Pin 5 GND=
Pin 6 5.1V= 5.13
Pin 7 5.1V= 5.13
Pin 8 O/N= 0.00
Pin 9 O/F= 0.00

If the signal card connected reconnected to AC power
Pin 1 B-Dim= 0.02
Pin 2 13V= 13.41V
Pin 3 GND=
Pin 4 GND=
Pin 5 GND=
Pin 6 5.1V= 5.13
Pin 7 5.1V= 5.13
Pin 8 O/N= 0.00
Pin 9 O/F= 0.00

The part number of IC801S is FSGM300N

Those are the test i did,

Thanks very much.

tama4tama

[PlainBill]

Re: Samsung SyncMaster B1940

Without the signal card connected
Pin 1 B-Dim= 0.00
Pin 2 13V= 12.96V
Pin 3 GND=
Pin 4 GND=
Pin 5 GND=
Pin 6 5.1V= 5.13
Pin 7 5.1V= 5.13
Pin 8 O/N= 0.00
Pin 9 O/F= 0.00

If the signal card connected reconnected to AC power
Pin 1 B-Dim= 0.02
Pin 2 13V= 13.41V
Pin 3 GND=
Pin 4 GND=
Pin 5 GND=
Pin 6 5.1V= 5.13
Pin 7 5.1V= 5.13
Pin 8 O/N= 0.00
Pin 9 O/F= 0.00

The part number of IC801S is FSGM300N

Those are the test i did,

Thanks very much.

tama4tama

Those numbers seem to indicate the power supply is working properly. This next series of tests are going to get a bit more complicated. You may want to have an assistant.

The first step is easy - if you haven's already done so, hook the cable from the control panel of the monitor to the signal card. With power applied, measure the voltage at pins 1, 8, and 9 of the connector on the power supply while you press the power button slowly several times, and note if the voltage on any of the pins change.

For the next step, I have marked up the picture of the signal card.

I have labeled a connector that I believe goes to the control (front) panel of the monitor. With the power supply and front panel connected, power supply connected to AC, check the voltage on each of these pins as you press the Power button. Does the voltage change on any pins?

There are two ICs circled in yellow, I believe they are IC601 and IC602. What are the numbers on each of these?

There are three components circled in orange. What is the identifier printed on the circuit board next to each of them?

There are two components circled in red. One of them may have an identifier on the circuit board of Q501, it's hard to tell. What are the identifiers.

If you have any questions about purpose of any test, let me know.

PlainBill

[tama4tama]

Re: Samsung SyncMaster B1940

The two ICs circled in yellow, are IC601 has S02 K41and IC602 has S01 K51.
The three components circled in orange are BD401, BD402 and R616
The two components circled in red. There are Q601 and Q602 which has SKW 04 on them.

Now to my test and the out comes.
Pin 1 0.00
Pin 8 7.0
Pin 9 0.00

When I did test again the front light come up and can not go off again and this is the voltage.
Pin 1 3.25
Pin 8 0.0
Pin 9 3.00

I hope I did not screw up board.

tama4tama

[PlainBill]

Re: Samsung SyncMaster B1940

The two ICs circled in yellow, are IC601 has S02 K41and IC602 has S01 K51.
The three components circled in orange are BD401, BD402 and R616
The two components circled in red. There are Q601 and Q602 which has SKW 04 on them.

Now to my test and the out comes.
Pin 1 0.00
Pin 8 7.0
Pin 9 0.00

When I did test again the front light come up and can not go off again and this is the voltage.
Pin 1 3.25
Pin 8 0.0
Pin 9 3.00

I hope I did not screw up board.

tama4tama

I do not believe you screwed up the board, but the board is not working. The voltages you got indicate the board is turning the backlights on. The fact that it no longer responds to the power button indicates a problem on the signal card.

It is very likely IC601 and IC602 are the voltage regulators, but the marking codes are not in any database. At this point there are only a few tests possible.

I've marked up the original pictures.

On the signal card I have labeled the pins of IC602, as well as identifying a good point for the Ground lead of a DMM. The pinout of IC601 is identical.

With the signal card connected to the power supply, and the power supply plugged in, what are the voltages on each of the pins of IC601 and IC602?

On the power supply, what is the brand of the capacitors circled in red?

PlainBill

[tama4tama]

Re: Samsung SyncMaster B1940

These are voltages the on IC601 and IC602

IC601
Pin 1 2.55v
Pin 3 0.02v
Pin 4 5.12v
Pin 6 3.31v

IC602
Pin 1 2.57v
Pin 3 0.02v
Pin 4 4.34v
Pin 6 1.79v

There are five Sam Young capacitors
And one each of NXB and Rubycon capacitors

I will like to say here that I very grateful for all your kind help giving me on this subject.
Thank you Mr. PlainBill
tama4tama

[PlainBill]

Re: Samsung SyncMaster B1940

These are voltages the on IC601 and IC602

IC601
Pin 1 2.55v
Pin 3 0.02v
Pin 4 5.12v
Pin 6 3.31v

IC602
Pin 1 2.57v
Pin 3 0.02v
Pin 4 4.34v
Pin 6 1.79v

There are five Sam Young capacitors
And one each of NXB and Rubycon capacitors

I will like to say here that I very grateful for all your kind help giving me on this subject.
Thank you Mr. PlainBill
tama4tama

I'm sorry, I wasn't clear. I would like the voltage on all 6 pins of each IC. I still have hopes of identifying them.

There are some mysteries here, but if I assume pin 6 is the output, these are providing 3.3 volts and 1.8 volts, exactly the voltages the processor requires.

At this point, I don't have much hope for successfully repairing this. There is no obvious problem. the only suggestion I can make would be to replace the capacitors on the power supply with some of the brands and series in this list, but I don't have any confidence this would help. The other possibility would be to replace the signal card.

PlainBill

[tama4tama]

Re: Samsung SyncMaster B1940

The voltages
IC601
Pin 2 0.00v
Pin 5 0.00v

IC602
Pin 2 0.00v
Pin 5 0.00v

It seems I need to order for a new card, there is no hope repairing this card.
Mr. Plain Bill, I once again like to thank you from the bottom of my heart. Thanks have a great weekend.

Thank you
tama4tama