Samsung SyncMaster 226BW

[PlainBill]

Re: Samsung SyncMaster 226BW

Thank you PlainBill,
I just feel like trying my best to get it to work, before buying another board for $30 on ebay.
I believe the source of all problems was my flux. During soldering one of the capacitors,i accidently spilled too much flux. I assume the flux is causing shorts and im testing many components on the board with my multimeter and comparing to the other board, most match, but those who don't usually do match after some rubbing with alcohol or reflowing the solder.
So maybe there is nothing wrong with this board, in fact it was working good before replacing the capacitors, except that it was flickering when it was cold until the monitor was warmed up.
The CCFLs are good, i hooked up a power supply board from another 226BW and the monitor was working perfectly.
I will check the BL_ON thing.

I am trying to clean the board with alcohol, but the alcohol leaves white marks after drying up and doesn't seem to really remove any shorts caused by the flux spill during my soldering of one of the capacitors near the inverter IC.

Any tips for good cleaning? Is it safe to use a brush on this? it might knock off a resistor.

Thanks a lot,
mastertheknife.

The resistors should be securely soldered in place. I use a toothbrush (not the same one I use on my teeth) to scrub the board.

Otherwise, you seem to be having good help.

PlainBill

[mastertheknife]

Re: Samsung SyncMaster 226BW

Thank you PlainBill.

With me on the multimeter and my brother turning on\off the monitor multiple times and later hitting the source button(turns on backlight for 1 sec) i managed to measure pin2(OVP) and pin10(open lamp protection) multiple times.

pin2 (Overvoltage protection) is always 0.0V but when the backlight turns on, highest i saw was 0.08V
pin10 (Voltage control loop compensation) is always 0.0V too but when the backlight turned on, its usually between 2.2V to 2.7V with highest i saw was 2.7V.

I will now measure pin9 (Feedback sense).

Thanks again,
mastertheknife.

[mastertheknife]

Re: Samsung SyncMaster 226BW

Th3_uN1Qu3,

I measured pin9 (Feedback control) like you said.
Its 0.0V but when the backlight is on\turns on the highest i saw from this pin was 0.17V

Thank you,
mastertheknife.

[Th3_uN1Qu3]

Re: Samsung SyncMaster 226BW

(Voltage control loop compensation) is always 0.0V too but when the backlight turned on, its usually between 2.2V to 2.7V with highest i saw was 2.7V.

You might have a problem here, but something tells me it's not this.

The other ones look normal - of course you're going to see zero volts when the inverter isn't operating. Though, i'd expected a higher voltage on the OVP pin when the backlight did turn on. Looks like something is loading the supply down. Repeat measurements on good board if you can.

[mastertheknife]

Re: Samsung SyncMaster 226BW

You might have a problem here, but something tells me it's not this.

The other ones look normal - of course you're going to see zero volts when the inverter isn't operating. Though, i'd expected a higher voltage on the OVP pin when the backlight did turn on. Looks like something is loading the supply down. Repeat measurements on good board if you can.

I'm afraid i can't solder on the good board, with my bad luck, i might kill the good board too.
I just tried to reflow the solder again on the transformers and some other components, but no luck, the 2 seconds to black problem still occurs.

Thanks,
mastertheknife

[Th3_uN1Qu3]

Re: Samsung SyncMaster 226BW

Then leave the good board be, and focus on this one. Also track and measure the rail from which the inverter MOSFETs are operating.

[alexanna]

Re: Samsung SyncMaster 226BW

2) The yellow dots gives 1076 ohms in 2K mode (the multimeter actually displays 1.076)

3) The red gives 1089 ohms in 2K mode (the multimeter actually displays 1.089)

Thank you again,
mastertheknife.

I very quickly read though this thread, Are we still having a 2 second to black problem?
And have I done the math correctly, the difference in the readings of the transformers seem just a tad bit high
Or did I miss something?
Al

[mastertheknife]

Re: Samsung SyncMaster 226BW

I very quickly read though this thread, Are we still having a 2 second to black problem?
And have I done the math correctly, the difference in the readings of the transformers seem just a tad bit high
Or did I miss something?
Al

Yes, the current problem is a 2 second to black problem. (Earlier i had a different problem, possibly caused by a short from a flux residue but thats gone now).
It started after replacing bad plagued caps that caused the backlight to flicker until the monitor was warmed up.

I have a question, is it likely that the new caps might be bad\defective although are looking in good shape? I ask this because i noticed a voltage drop in the backlight_on pin (coming from the signal board) when the backlight is being fired up. (drops from 3.94V to about 2.0V, maybe even less). Is there a way i can check their capacitance with a simple digital multimeter?
On the good board i am unable to read the voltage with the backlight off (the other board works) but i measured 3.93V.

By the way, im not sure if my problem is 2 seconds to black, it seems shorter than 2 seconds, more like a second or less.

mastertheknife.

[jetadm123]

Re: Samsung SyncMaster 226BW

I have a question, is it likely that the new caps might be bad\defective although are looking in good shape? I ask this because i noticed a voltage drop in the backlight_on pin (coming from the signal board) when the backlight is being fired up. (drops from 3.94V to about 2.0V, maybe even less). Is there a way i can check their capacitance with a simple digital multimeter?
On the good board i am unable to read the voltage with the backlight off (the other board works) but i measured 3.93V.

By the way, im not sure if my problem is 2 seconds to black, it seems shorter than 2 seconds, more like a second or less.

mastertheknife.

I've been meaning to ask you what series of Nichicon caps did you use? PW? HE? The series is stamped on the cap label.

[mastertheknife]

Re: Samsung SyncMaster 226BW

I've been meaning to ask you what series of Nichicon caps did you use? PW? HE? The series is stamped on the cap label.

The 820uF and 680uF ones are PW series, and the 330uF one is a VZ and they are all rated for 105C.
The 47uF i put the stock one back to troubleshoot, but it doesnt seem to be a nichicon cap, it says CHNG on it or something like that.
I didn't order them from digikey because digikey wants $40 for international shipping so i had to order them from ebay (226bw repair kit - 6 capacitors)

mastertheknife

[alexanna]

Re: Samsung SyncMaster 226BW

I very quickly read though this thread, Are we still having a 2 second to black problem?
And have I done the math correctly, the difference in the readings of the transformers seem just a tad bit high
Or did I miss something?
Al

Well I owe you a big apology, I have no idea where my mind was yesterday but my math was totally wrong on the inverter transformers
You do still have what is called a two second to black problem.
The data sheet for the controller states 2.4 volts is the low threshold for the BL on pin, If you are indeed going below that it could be a problem. Help me out I probably missed it, where are you measuring the voltage going below the 2.4 volts?
Al.

[mastertheknife]

Re: Samsung SyncMaster 226BW

Well I owe you a big apology, I have no idea where my mind was yesterday but my math was totally wrong on the inverter transformers
You do still have what is called a two second to black problem.
The data sheet for the controller states 2.4 volts is the low threshold for the BL on pin, If you are indeed going below that it could be a problem. Help me out I probably missed it, where are you measuring the voltage going below the 2.4 volts?
Al.

Yes. I measured 3.94V directly on the pin it enters the board from the signal board. The many resistors on the way probably step down the voltage to the acceptable range of the IC. The worrying thing is that once the backlight is fired on, it spikes down to as low as 1.0V!
On a good board i measured 3.93V with backlight on. I am unable to monitor on the good board for a voltage change because its either 0.0V (monitor off) and 3.93V (monitor on - backlight on).
How likely is it to be the new capacitors? The new ones (nichicon low-esr pw series, 105C) might be leaky or something, although on the outside look perfectly in good shape.

EDIT: I just checked all transistors with the multimeter for shorts (<200 ohms) on all legs and they are all ok.

Thank you,
mastertheknife

[alexanna]

Re: Samsung SyncMaster 226BW

^
I am going to stay from the capacitor question at the moment.
On the monitors I have worked on that have had some type of second to black problem, caused by a caused by a defective a ccfl, inverter transformer ect.The back light on signal has always been above the lower specification for back lights to be on, if I interpreted the data sheet correctly .yours is about 2.3volts.
After the second to black problem occurs and the lamps are off what is the voltage on ENA pin #3 of the oz controller? You will need a video source hooked up.
Al

[mastertheknife]

Re: Samsung SyncMaster 226BW

I did an interesting test.

It may sound stupid, but i soldered back the original caps (bad) to see if the original problem will return (backlight flicker until monitor warm enough)
But it didn't! With the original capacitors, the backlight didn't fire up at all!
I now put back the nichicon caps and the 2 seconds to black problem is back, so its probably not the new capacitors.

I will try summarize all the tests i've done in case anyone wants to join in and help, this should avoid reading the previous pages.

The Problem: Samsung 226BW, 2 seconds to black (backlight only) after replacing bad caps with new ones, the problem was the backlight flickering until the monitor was warmed up.

Sources of the problem eliminated:
1) The CCFLs, the panel and the logic board - Works perfectly when an identical power supply board from another 226BW is used.

Things checked:
1) Transistors for shorts - OK, no connection between any legs under 200 ohms.
2) Inverter transformers - OK, one measured 1094 and one 1080 ohms.
3) Bad solder joints - OK, Reflowed solder on pretty much every component on the board and verified all joints with magnifying glass
4) Backlight_ON signal - OK, signal board provides 3.94V at all times the monitor is on.
5) Overvoltage protection - OK, max measured voltage on OVP pin was 0.08V
6) Current feedback pin - OK, max measured voltage on pin was 0.17V.
7) Open-lamp protection - Not sure, max measured voltage was 2.7V!
8) Board voltage - OK, 13.24VDC stable, which is between the desired voltage of 13-13.5VDC.
9) Inverter section voltage - OK, 13.24VDC through fuse F301.
10) Inverter IC voltage - Not sure, unstable, jumps between 4.6V and 5.0V.
11) Fuses - OK, F101 and F301 are about 0.0 ohms

What i know so far:
-When the backlight fires up, there is a voltage drop. I measured the Backlight_ON pin from the signal board dropping from 3.94V to as low as 2.0V.
-Adjusting the brightness (e.g. from high to lowest) doesn't help.
-Monitor works perfectly when an identical power supply board is used.
-Putting back the old capacitors doesn't fix the problem, the backlight doesn't turn on at all with the old capacitors.
-Turning off and back on the monitor brings the backlight working again for a second or two.
-Hitting the source button also brings the backlight working again for a second or two.

Board: IP-45130A Rev 0.1
Inverter IC: OZ964GN (datasheet: http://www.alldatasheet.com/datashee...2/OZ964GN.html)
Pictures attached.

[retiredcaps]

Re: Samsung SyncMaster 226BW

Sources of the problem eliminated:
1) The CCFLs, the panel and the logic board - Works perfectly when an identical power supply board from another 226BW is used.

For fun, what about the other way? That is "bad" power/inverter board inside the "other" 226BW?

[mastertheknife]

Re: Samsung SyncMaster 226BW

For fun, what about the other way? That is "bad" power/inverter board inside the "other" 226BW?

I will try that but that might take some time because i am too busy during the week working days. But even if it works, its not a good workaround because im not interested in swapping panels. My panel is good and the other one has some scratches on it.

I also followed the reference application in the OZ964GN datasheet and compared it to the board, the board's circuit is almost identical to the reference application but with some differences. I also measured many resistors on both boards and compared them, they pretty much all match except the one on the VDDA pin.

There's something that puzzles my mind. I couldn't figure out how the inverter IC gets its voltage. The VDDA pin (Supply voltage) is attached to a resistor (5Kohms in the good board, 3Kohms in the bad) and the other side of the resistor is ground (0.0 ohms to ground). So how exactly does it get its 5V supply voltage and what steps it down to 5V from the board voltage of 13V? All i know is that power to the inverter section of the board is carried via fuse F301. I'm also worried why the supply voltage (measured at VDDA pin) was unstable, jumping all the time from 3V to 5V, mostly between 4.6V to 5V.

I have attached a picture. I will try getting a closer one when i find some time and the camera's battery charger

Thanks everyone for their time and willingness to help,
mastertheknife.

[jetadm123]

Re: Samsung SyncMaster 226BW

I will try that but that might take some time because i am too busy during the week working days. But even if it works, its not a good workaround because im not interested in swapping panels. My panel is good and the other one has some scratches on it.

I also followed the reference application in the OZ964GN datasheet and compared it to the board, the board's circuit is almost identical to the reference application but with some differences. I also measured many resistors on both boards and compared them, they pretty much all match except the one on the VDDA pin.

There's something that puzzles my mind. I couldn't figure out how the inverter IC gets its voltage. The VDDA pin (Supply voltage) is attached to a resistor (5Kohms in the good board, 3Kohms in the bad) and the other side of the resistor is ground (0.0 ohms to ground). So how exactly does it get its 5V supply voltage and what steps it down to 5V from the board voltage of 13V? All i know is that power to the inverter section of the board is carried via fuse F301. I'm also worried why the supply voltage (measured at VDDA pin) was unstable, jumping all the time from 3V to 5V, mostly between 4.6V to 5V.

I have attached a picture. I will try getting a closer one when i find some time and the camera's battery charger

Thanks everyone for their time and willingness to help,
mastertheknife.

Here's my guess. The power supply outputs 13V only. There's a wiring harness that connects the power board to the logic board. One of the wires on the harness is probably labeled 13V. The logic board usually requires 1.8V, 3.3V and 5V to function properly. I suspect the 13V feeds a 5V voltage regulator on the logic board, where the 5V output of the regulator is split between the logic board and the OZ964 through another wire on the harness (maybe labeled 5V?). Once you locate the 5V regulator, measure it's output to see if it's fluctuating.

[mastertheknife]

Re: Samsung SyncMaster 226BW

Here's my guess. The power supply outputs 13V only. There's a wiring harness that connects the power board to the logic board. One of the wires on the harness is probably labeled 13V. The logic board usually requires 1.8V, 3.3V and 5V to function properly. I suspect the 13V feeds a 5V voltage regulator on the logic board, where the 5V output of the regulator is split between the logic board and the OZ964 through another wire on the harness (maybe labeled 5V?). Once you locate the 5V regulator, measure it's output to see if it's fluctuating.

The logic\signal board runs off 13VDC (measured 13.24V) and theres no 5V pin:
Pin1 = PWM-DIM
Pin2,3,4 = GND
Pin5,6,7 = 13V
Pin 8 = A-DIM
Pin 9 = ON/OFF (Backlight_on pin, measured at 3.94V at all times)
Power to the inverter section of the board is carried through fuse F301 and i measured it to be 13.24V too, so there has to be something that steps the voltage down to 5V. Maybe its the resistor in the picutre, but why its other side is connected to ground? I'm confused.

mastertheknife

[jetadm123]

Re: Samsung SyncMaster 226BW

What is the part number for U310? It's on top of the board right above the black arrow marked "DIP"


Oops! Sorry, I meant U301.

[jetadm123]

Re: Samsung SyncMaster 226BW

The logic\signal board runs off 13VDC (measured 13.24V) and theres no 5V pin:
Pin1 = PWM-DIM
Pin2,3,4 = GND
Pin5,6,7 = 13V
Pin 8 = A-DIM
Pin 9 = ON/OFF (Backlight_on pin, measured at 3.94V at all times)
Power to the inverter section of the board is carried through fuse F301 and i measured it to be 13.24V too, so there has to be something that steps the voltage down to 5V. Maybe its the resistor in the picutre, but why its other side is connected to ground? I'm confused.

mastertheknife

You may be dealing with a multi-layered pc board, which has copper traces on different layers of the circuit board. This is used when the designer can't fit all the traces on the outer most layer. That may be why it "appears" that there's just that one resistor tied to VDDA of the OZ964.

What's the part # of U301? It could be the voltage regulator.