Samsung Syncmaster 225BW

[retiredcaps]

Re: Samsung Syncmaster 225BW

In this same megathread, this picture

https://www.badcaps.net/forum/attach...3&d=1260133724

shows 3 lines of letters. I think I can make out OZ964. See if yours is the same. Or it could OZ9938.

[retiredcaps]

Re: Samsung Syncmaster 225BW

that stamping is real hard to read...from what I can make out it is 64GN T005322p.

I'm not having luck finding such a part?

Can you clean up the chip with a bit of isopropyl alcohol and try reading it again?

Do you have a magnifying glass or jewelers loupe?

Or use a camera with a good macro mode?

Meter is just a fluke 87.

I'm jealous.

[nmjwolf]

Re: Samsung Syncmaster 225BW

that stamping is real hard to read...from what I can make out it is 64GN T005322p.

Meter is just a fluke 87.

Thanks for your help so far!

[retiredcaps]

Re: Samsung Syncmaster 225BW

voltage levels don't bother me I deal with 4160V AC on a daily basis.

On this forum, I have no clue about people's background or experience so I always side with caution. We had some people doing scary things with their multimeter. Black probe in Amps jack, measuring the high voltage side with meter set on resistance, measuring resistance with power on, etc.

The last thing to check is on the back of the pcb. There is a 20 pin IC. What is the part number?

This is the inverter pwm chip. It controls whether the backlights come or not.

If the pwm checks out, then I think you can rule out the inverter part of the board as being bad and check the ccfls. With the ccfls, you are looking for stuff like these pictures.

http://s807.photobucket.com/albums/y...klight%20lamp/

PS. What type of multimeter?

[nmjwolf]

Re: Samsung Syncmaster 225BW

those both measure 13.16VDC

voltage levels don't bother me I deal with 4160V AC on a daily basis.

[retiredcaps]

Re: Samsung Syncmaster 225BW

C305 and C306 0VDC measurement made on either side of caps to GND
C303 and C304 0VDC measurement made on either side of caps to GND

NO, not the blue caps. Stay away from those caps, they are high voltage.

The Panasonic electrolytic caps (circled in red). Measure the DC voltage across the legs of the caps. Black probe to negative and red probe to positive.

[nmjwolf]

Re: Samsung Syncmaster 225BW

F301 13.1VDC - 13.1VDC => fuse good
C305 and C306 0VDC measurement made on either side of caps to GND
C303 and C304 0VDC measurement made on either side of caps to GND

[retiredcaps]

Re: Samsung Syncmaster 225BW

do the CCFLs have to be plugged in for the measurements?

Yes. We want everything plugged in. Use cardboard if necessary to prevent boards from shorting.

[nmjwolf]

Re: Samsung Syncmaster 225BW

do the CCFLs have to be plugged in for the measurements?

[retiredcaps]

Re: Samsung Syncmaster 225BW

t301=1096
t302=1091

Both the secondary windings look good.

With power on and lcd plugged in ...

1) What is the DC voltage on either side of F301? You should have 2 measurements.

2) What is the DC voltage across the two Panasonic caps flanking U302 and U303? You should have 2 measurements.

[nmjwolf]

Re: Samsung Syncmaster 225BW

t301=1096
t302=1091

[nmjwolf]

Re: Samsung Syncmaster 225BW

No I do not believe the backlights are coming on and that is why i can barley make out my desktop.

I have not found any shorts on u301.

[retiredcaps]

Re: Samsung Syncmaster 225BW

4) T301 and T302 are your inverter transformers. It looks like the pins that connect to the blue caps (C303/C304 and C305/306) are the secondary winding pins.

Measure the resistance between the secondary pins on T301. Report reading. Do the same for T302.

They should be within 3% of each other.

[retiredcaps]

Re: Samsung Syncmaster 225BW

1) Please answer if the backlights come on or not?

2) U301 is some sort of transistor. Check it for a short.

3) The readings for the mosfets suggest they are good.

[nmjwolf]

Re: Samsung Syncmaster 225BW

F301 is good 0.1 ohms.

Using the datasheet found here:

I got:
U302
a) black on pin S1- red on pin G1 - record ohms => 3.68M ohm
b) black on pin S1- red on pin D1 - record ohms => .3M ohm
c) black on pin G1- red on pin D1 - record ohms => 3.88M ohm
a) black on pin S2- red on pin G2 - record ohms => 4.1M ohm
b) black on pin S2- red on pin D2 - record ohms => .3M ohm
c) black on pin G2- red on pin D2 - record ohms => 2.95M ohm


U301
a) black on pin S1- red on pin G1 - record ohms => 3.65M ohm
b) black on pin S1- red on pin D1 - record ohms => .3M ohm
c) black on pin G1- red on pin D1 - record ohms => 3.87M ohm
a) black on pin S2- red on pin G2 - record ohms => 4.05M ohm
b) black on pin S2- red on pin D2 - record ohms => .3M ohm
c) black on pin G2- red on pin D2 - record ohms => 2.98M ohm

Thanks for the help so far!

[retiredcaps]

Re: Samsung Syncmaster 225BW

Also check the mosfets U302 and U303. A procedure for testing is at (under section mosfet)

https://www.badcaps.net/forum/showpo...4&postcount=19

[retiredcaps]

Re: Samsung Syncmaster 225BW

Are the backlights on? If not, check F301. A good fuse should measure less than 1.0 ohms.

[nmjwolf]

Re: Samsung Syncmaster 225BW

The screen does stay on...for hours just very dim.
The power LED does stay on (blue).

I do have a multimeter, but no other CCFL's to try out. I will read those posts and see what voltages to check hopefully that will point me in the direction of the part to replace next.

Thanks

[selldoor]

Re: Samsung Syncmaster 225BW

Hi Caps are panasonic -Fm so should be good .They appear to be in right way around. Im assuming you changed like for like value wise- When it gets fixed you
should really change the ( from memory 47uf 50v) one
Does the screen stay on but dark for some time - (more than 5 mins).
Does the power led stay lit ( I would guess it does but best to ask)
It appears to be the ccfls or the inverter board at fault - If you read the posts by Gammaray starting at post404 in this thread there is quite a bit of information and tests you can do mainly suggested by Alexanna. The one on the inverter transformer and the fuses are probably the first to try.
Have you got a multimeter you can use and either a spare ccfl or another monitor
or laptop screen that you can connect to the inverter board ( It doesnt need to be working as long as it has one ccfl that is good.

[Konesky]

Re: Samsung Syncmaster 225BW

Nmjwolf,

I'm not sure if this will solve the issue or not but as Selldoor mentioned, the surgery typically involves replacing 6 caps, not 5. Having done it 3x myself, I can see "C107" on your board is original. (It's the small one at the very bottom of the first picture, dead center)

I can confirm you've got the correct polarity for the caps you've replaced although double check the properties of your caps against the list in this thread to ensure they are the correct voltage and type (ESR) in addition to being the correct capacitance.