Help me troubleshoot this power supply. FSP043

[JonathanAnon]

Hi everybody, long time lurker here with my first post. Been trying to fix a power supply board FSP043, which is from a Fujitsu Siemens ScaleoView L-19 LCD Monitor, though it is also used in a lot of Acer screen as well...

What I have done so far.

- I have replaced most of the electrolytic caps, marked in yellow in the schematic below. I did NOT replace the main filter cap, but my voltmeter says that it is okay.
- I have checked the outputs of a working FSP043, and the 5v rail voltages on this board match those on the working board. However, the 12v rails on the working board read as 12.8v, but this board only read as 11.78v (point B in the diagram below).
- I tested the output of the Dual Schottky Diodes (point A in the diagram below) and it also reads 11.78v. This should be much higher shouldnt it? I tried testing at Dual Schottky Diode input, connecting the positive to the input and the negative to the metal case, but this reads as 0.
- I havent tested the MOSFET or the transformer. But the transformer seems to work okay for the 5v rail.



I would appreciate any help you could offer. I have a multimeter but no scope.

thank you :-)

[Khron]

Re: Help me troubleshoot this power supply. FSP043

Have you tried hooking up some loads to the outputs? Like some car lightbulbs...

Some psu's need some load on the 5v and/or 3.3v outputs, in order to regulate the 12v properly. On the other hand, 11.78v on the 12v output *IS* within spec, according to the ATX standard (12v +/-5%)...

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

I didnt have a 12v bulb, so I tried a 12v CPU fan on both of the 12v rails that feed the video board, and the fan DID work in both. But that 12v rail also serves the inverter board which does not light up the backlight of a screen that I know to be working.

[Khron]

Re: Help me troubleshoot this power supply. FSP043

Is the inverter itself definitely working ok (with another 12v supply)? Being so "touchy" about less than a quarter of a volt sounds a bit "suspicious" to me...

[budm]

Re: Help me troubleshoot this power supply. FSP043

When the inverter receives the 12V from this power supply, for the backlights to be on, it will need BL_ON command for the logic/main board to turn on the lights.
Is the monitor attached to working PC?
What is the exact voltage reading on the 5V? 5.2V as shown in the diagram?

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Screen 1 (replaced capacitors, still not working):
DC1: 11.75v
DC2: 11.75v
DC3: 5.15v
DC4: 4.85v

Screen 2 (working):
DC1: 12.79v
DC2: 12.79v
DC3: 5.15v
DC4: 4.83v

My volt meter only goes to 600VAC and thus cant read the 720VAC outputs on the inverter... nb.. the inverter is on the same board as the power supply so I cant try a separate power supply like you suggested.

When the inverter receives the 12V from this power supply, for the backlights to be on, it will need BL_ON command for the logic/main board to turn on the lights.

okay this may be important, because I'm pretty sure the video board is blown in Screen 1... I tried it with screen 2 and it would not work. So maybe that explains the backlight not coming on regardless of voltage... (I didnt want to try the good video board from screen 2 with power board from screen 1 in case I would end up with two broken monitors..)

I would actually buy a new video board if I thought that it would work with the 11.79v supply from the board, but it seems like a big discrepancy.. Any way I could test the Schottky input and the transformer output before I buy a video board?

[budm]

Re: Help me troubleshoot this power supply. FSP043

You do not want to test the output voltage of the inverter, it can put out about 2000V!, that will blow your meter input circuits easily.
Do you have the diagram for the rest of the monitor, then I can tell you how to simulate the BL_ON signal.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

I searched high and low for the service manual for the L9ZA, but I couldnt find it. However this ACER monitor has the same video board DAOL9FMB031 and almost identical power board FSP043-2PI02S.

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Any chance of some good clear pictures of the fronts and backs of the two boards.
We can help a lot more if you post good clear pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Video Board Front

https://www.badcaps.net/forum/attach...1&d=1342479087

Video Board Back

https://www.badcaps.net/forum/attach...1&d=1342479087

Power Board Front.

https://www.badcaps.net/forum/attach...1&d=1342480232

Power Board Back.

https://www.badcaps.net/forum/attach...1&d=1342480232

:-( Had a good few goes at taking the photos but this is the best I can do for tonight..

[ben7]

Re: Help me troubleshoot this power supply. FSP043

Video Board Front

https://www.badcaps.net/forum/attach...1&d=1342479087

Video Board Back

https://www.badcaps.net/forum/attach...1&d=1342479087

Power Board Front.

https://www.badcaps.net/forum/attach...1&d=1342480232

Power Board Back.

https://www.badcaps.net/forum/attach...1&d=1342480232

:-( Had a good few goes at taking the photos but this is the best I can do for tonight..

Hm, those links don't work for me...

I think your mainboard has a broken voltage regulator on it, since it doesn't work in either of the monitors.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Hm, those links don't work for me...

arrrgghhh, sorry.. I uploaded those and linked to them but the server seemed to remove them when I didnt keep them as attachments.. View them here.

Power Board Front
http://omg.wthax.org/powerboardfront.jpg

Power Board Back
http://omg.wthax.org/powerboardback.jpg

Video Board Front.
http://omg.wthax.org/videoboardfront.jpg

Video Board Back.
http://omg.wthax.org/videoboardback.jpg

I think your mainboard has a broken voltage regulator on it, since it doesn't work in either of the monitors.

That is what I thought initially, but there is no dedicated voltage regulator on the board.. (have a look at the schematic in my original post and see what you think) It seems that the secondary side of the SMPS transformer gives out twelve volts to the input of the dual schottky diodes? I dont know how to measure the input of the Schottky diode, if anybody could suggest how I do this I will confirm the input voltage at this point.

[ben7]

Re: Help me troubleshoot this power supply. FSP043

[QUOTE=JonathanAnon;251882]

Hm, those links don't work for me...

arrrgghhh, sorry.. I uploaded those and linked to them but the server seemed to remove them when I didnt keep them as attachments.. View them here.

Power Board Front
http://omg.wthax.org/powerboardfront.jpg

Power Board Back
http://omg.wthax.org/powerboardback.jpg

Video Board Front.
http://omg.wthax.org/powerboardfront.jpg

Video Board Back.
http://omg.wthax.org/powerboardback.jpg




That is what I thought initially, but there is no dedicated voltage regulator on the board.. (have a look at the schematic in my original post and see what you think) It seems that the secondary side of the SMPS transformer gives out twelve volts to the input of the dual schottky diodes? I dont know how to measure the input of the Schottky diode, if anybody could suggest how I do this I will confirm the input voltage at this point.

The power board is not the video board

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

The power board is not the video board

Not having a good day today :-( (it's fixed now, I think)..

[ben7]

Re: Help me troubleshoot this power supply. FSP043

Not having a good day today :-( (it's fixed now, I think)..

Yep its fixed.

The mainboard does have a voltage regulator on it. Can you tell us what is written on it?

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Sorry ben, I was talking about the power board. I havent tackled fixing the video board, I was really just trying to get the broken power board to where it's DC outputs read the same as the working power board's DC output... and then take it from there.

I posted the image of the video board as one of the guys above was gonna tell me how to see if I could trigger the backlight to turn on by emulating the command sent from the video board... but this was just to test the power board. (but to answer your question the number the video board regulator is 6F8L 1117L, searched it but cant find a datasheet ).

[rogfanther]

Re: Help me troubleshoot this power supply. FSP043

It is a LM1117. If no other numbers, and from the look of the two resistors near its leg, seems to be a -ADJ version, with the resistors used to configure it.

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Hi - what was fixed? the pictures or one of the boards?

This is how to test Voltage Regulators (from retiredcaps guide)

Voltage regulators (U designation) can be bad. They can be shorted or output the incorrect voltage. The test described below only tests the former.

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test voltage regulators "in circuit" for shorts by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted voltage regulator. Remove from circuit and repeat the tests to verify.

[JonathanAnon]

Re: Help me troubleshoot this power supply. FSP043

Hi selldoor. again it was the power board that I am focussing on.. (as I think the video board looks a lot more complex, and more than I'm capable of fixing).. But to answer your question.. The measurements for the LM1117 voltage regulator on the video board.

a) black on pin 1- red on pin 2 - 0.198 K ohms
b) black on pin 1- red on pin 3 - 1.237 K ohms
c) black on pin 2- red on pin 3 - 0.968 K ohm

(I had to change to the K ohms scale)

[selldoor]

Re: Help me troubleshoot this power supply. FSP043

Ok - that looks good - next time its all fitted up check the voltage on the
three legs - ignore the fat tab.
Someone has suggested that the power supply may be within spec so 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.
I attach a pic and with the power off meter on ohms 2000 check s1>S2 and S3 >S4