Help me troubleshoot this power supply. FSP043

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Okay, I hooked up the power board and the video board, verified that the voltages coming out of the power board were the same as previous ... i.e. 11.78, 11.78, 5.15, 4.85, and took the voltage measurements of the LM1117L voltage regulator on the video board... Here are the numbers:

black to pin 1, red to pin 2 : 1.25v
black to pin 1, red to pin 3 : 2.44v
black to pin 2, red to pin 3 : 1.18v

... an easy test if we can find the right pins is to test the secondary windings on the inverter transformer. My guess would be that there are two secondaries one at each end of the transformer.

Is there anyway that I could check the main SMPS transformer first? Remember the 5v rails on the power board are reading the same as a working power board. It is only the two DC 12v rails that are reading approx 1v below the working power board. I understand what people are saying about that 11.78v is within the 12v +/-5%, but it just seems wrong to me..

[budm]

Re: Help me troubleshoot this power supply. FSP043

What do you read on Pin 1 and Ground, Pin 3 and ground? Ground = metal chassis (board must be mounted in place)

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

What do you read on Pin 1 and Ground, Pin 3 and ground? Ground = metal chassis (board must be mounted in place)

Because the voltage regulator is surface mounted, there are no pins on the rear side of the board. So when it is in it's metal casing I have no way of connecting to the voltage regulator... Could I use connection on the power board where the big screw goes in ... (both regulator and screw hole are highlighted in yellow on the image below).

http://omg.wthax.org/17072012826_copy.jpg

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Is there anyway that I could check the main SMPS transformer first? Remember the 5v rails on the power board are reading the same as a working power board. It is only the two DC 12v rails that are reading approx 1v below the working power board. I understand what people are saying about that 11.78v is within the 12v +/-5%, but it just seems wrong to me..

I dont think so - the result would not be conclusive. Voltages vary depending on what is actually working- The inverter transformer test is easy - you do not have to take it off the board - the picture is just like that to show the pins.
You just have to translate it into where they are on your board I think they are the 4 in an oblong covered in glue on the back of the board. It is just an ohms test - no power post results as S1>S2= xxx ohms S3>S4= XXXohms

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

It is just an ohms test - no power post results as S1>S2= xxx ohms S3>S4= XXXohms

Okay, your inverter transformer seems to be the same as mine... that image is very useful actually, as I was wondering what was in that unit without taking the cover off....

With the power off and MM set to 2K ohms, I took the following measurements..

S1 - S2 reads 1.014
S3 - S4 reads 1.010

[rogfanther]

Re: Help me troubleshoot this power supply. FSP043

Because the voltage regulator is surface mounted, there are no pins on the rear side of the board. So when it is in it's metal casing I have no way of connecting to the voltage regulator... Could I use connection on the power board where the big screw goes in ... (both regulator and screw hole are highlighted in yellow on the image below).

http://omg.wthax.org/17072012826_copy.jpg

You can measure to that screw hole marked "H2". Black lead in it, red lead in the 1117 pins.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Okay voltages between LM1117L and cold ground H1.

PIN1 - GND : 2.09V
PIN2 - GND : 3.35V
PIN3 - GND : 4.55V

While I had the video board hooked up to the PS for this test, I measured the voltage across the power supply's 12V DC output which feeds the video board and it read 12.15V.. It reads as 11.78V without load. Maybe it is working and I just need a new video board..

If I could get the BL_ON signal and test the backlight it would confirm it.

[rogfanther]

Re: Help me troubleshoot this power supply. FSP043

The 1117 voltages seem to be ok. It is converting 5V to 3.3V. I agree with the idea of testing with a known good video board. Didn´t you say that you had another display of the same model ?

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Okay, your inverter transformer seems to be the same as mine... that image is very useful actually, as I was wondering what was in that unit without taking the cover off....

With the power off and MM set to 2K ohms, I took the following measurements..

S1 - S2 reads 1.014
S3 - S4 reads 1.010

Those are good -so the inverter transformer seems ok.

Budm did ask some posts back if you had it connected up to a working PC - cant see an answer
Sometimes if it is not connected the mainboard wont start the inverter.

@Budm - you did say you had a BLon trick?

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

okay managed to put the LCD monitor fully back together and nothing happens.. no light, nothing.. Just to reiterate, I've tried the video board with a known FULL WORKING power supply from a similar monitor, so I'm assuming that after the power supply caps blew, too much power went to the video board and some component on it then blew also.

I have another LCD screen displaying the same characteristics after also having the caps replaced, so I assume it's the same fault. I cant justify spending 30 dollars on a new DAOL9FMB031 video board to test the PS fully, which is annoying, but I'll keep a lookout for a second hand one.

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Hi - can you disconnect the cable that goes from the main board to the
panel, then try and switch on and report what happens.

[ben7]

Re: Help me troubleshoot this power supply. FSP043

And if what selldoor mentioned didn't work, You might want to start checking caps on the video board, sometimes if a cap goes bad in the psu, it can take out others on different boards.

You also could hook up the 5v to the BL_ON pin via a resistor (use one somewhere around 1k ohms), and see if the backlights turn on.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Checked all the caps and they look fine on the video board. But I'll whip off the cover again and try all the above suggestions..

You also could hook up the 5v to the BL_ON pin via a resistor (use one somewhere around 1k ohms), and see if the backlights turn on.

I've found the pin on the Scalar chip, but the pins are TINY. I'm not sure I can jump from the regulator to the chip with a resistor without damaging something.

I wasnt gonna troubleshoot the Video board, but I've found the service manual for the DAOL9FMB031, so I'll give it a shot .. This is the board layout
http://omg.wthax.org/DAOL9FMB031_Schematic.jpg

And this is the flowchart of troubleshooting the board.
http://omg.wthax.org/DAOL9FMB031_Troubleshooting.jpg

[ben7]

Re: Help me troubleshoot this power supply. FSP043

Checked all the caps and they look fine on the video board. But I'll whip off the cover again and try all the above suggestions..


I've found the pin on the Scalar chip, but the pins are TINY. I'm not sure I can jump from the regulator to the chip with a resistor without damaging something.

I wasnt gonna troubleshoot the Video board, but I've found the service manual for the DAOL9FMB031, so I'll give it a shot .. This is the board layout
http://omg.wthax.org/DAOL9FMB031_Schematic.jpg

And this is the flowchart of troubleshooting the board.
http://omg.wthax.org/DAOL9FMB031_Troubleshooting.jpg

What I meant was doing it without the video card plugged in, only the power supply itself. You might have to do the same with the PS_ON connection, if there is one on this power supply.

And be careful, the high voltage for the ccfls will hurt if you touch it!

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

What I meant was doing it without the video card plugged in, only the power supply itself.

I've found the datasheet on the inverter chip and read through what all the pins do... tbh, it's a hard read, but I reckon pin 13 ENSYNC is the pin to switch the backlight on...

https://www.badcaps.net/forum/attach...9&d=1300019903

[ben7]

Re: Help me troubleshoot this power supply. FSP043

I've found the datasheet on the inverter chip and read through what all the pins do... tbh, it's a hard read, but I reckon pin 13 ENSYNC is the pin to switch the backlight on...

https://www.badcaps.net/forum/attach...9&d=1300019903

Nonono, I mean on the connector that connects the video card to the power supply. The pins should be labeled.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

I thought those 8 pins were just for providing power to the VGA board, I didnt realise the backlight on signal was sent through here..

This is a capture of the pins from above
http://omg.wthax.org/powerconnections.jpg

And the voltages I measured across those pins earlier with the MM.
http://omg.wthax.org/measured_voltages.jpg

I see the words ADJ and ON/OFF beside the 5v rails, I'm assuming that it's the ON/OFF which seems to be the bottom pins.

[ben7]

Re: Help me troubleshoot this power supply. FSP043

I thought those 8 pins were just for providing power to the VGA board, I didnt realise the backlight on signal was sent through here..

This is a capture of the pins from above
http://omg.wthax.org/powerconnections.jpg

And the voltages I measured across those pins earlier with the MM.
http://omg.wthax.org/measured_voltages.jpg

I see the words ADJ and ON/OFF beside the 5v rails, I'm assuming that it's the ON/OFF which seems to be the bottom pins.

Connect pin 4 to +12v through a 1k resistor, and see if the psu turns on.

When you do it, keep the video board disconnected from the psu, but keep the ccfls connected. See if the ccfls will light up.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Okay ben (and thanks for your help so far, really learning a lot) I've created a 1k circuit on my breadboard and connected two jump wires from it to the two pins mentioned above. The backlight flicks on for a fraction of a second (while the pins touch) and then goes off.

I'm unsure as to whether you meant to connect them or to just jump the pins give a 1 to switch on? (trying to be careful)

[ben7]

Re: Help me troubleshoot this power supply. FSP043

Okay ben (and thanks for your help so far, really learning a lot) I've created a 1k circuit on my breadboard and connected two jump wires from it to the two pins mentioned above. The backlight flicks on for a fraction of a second (while the pins touch) and then goes off.

Ah, it appears there is a problem in the backlight inverter.

Does the power supply turn off too(measure its output voltage(s) if your not sure)? Or, does the backlight not work until you disconnect and reconnect the resistor to the BL_ON pin?

Yes, we are sending it a '1', to tell it to turn on the backlight. The resistor will limit the current when [if] you touch the wrong pin.