Samsung 2253LW

[jahjhai]

Re: Samsung 2253LW

here are the pictures you have requested...

thanks and advance happy new year...

[budm]

Re: Samsung 2253LW

The power supply is working, otherwise you will not be getting the good 5V, and the 16VDC. The problem is in the inverter circuit or it is not getting the BL_ON from the main board. No need to concentrate on the power supply section, that is not the problem.
I need good clear pictures of the top and bottom side of your board so I can give you the test points to test.

[jahjhai]

Re: Samsung 2253LW

greetings... holidays make me busy fixing my things.. now i have the voltage reading for the components needed.. the 5V voltages are in good condition, yes i do understand logic circuits, they need 5 volts to operate to get low or high signals.

anyway the MBR20100CT has two terminals with 1 common cathode. the first i test has voltage reading of 5.33V on each anode.. while the other MBR20100CT has a higher voltage which is 18.88V and i tested this without the fuse resistor to determine whats goin on...

also i have some voltage data for the DM0565R
Pins in Order:
1. Drain = 302V
2. GND
3. Vcc = 14.82V
4. FB = 0.647V
5. NC
6. Vstr = 296V

AC supply is 220V

with a fuse resistor voltage is 16V
without it becomes 18V

backlight nevers lights up..

[Davi.p]

Re: Samsung 2253LW

Sorry for my last post, i have read for error only the first page..

[budm]

Re: Samsung 2253LW

The reason I ask if the 5V is OK or not is that both voltages are generated by the same transformer, if the one goes up, another one will be up also since it is driven by the same transformer, the regulation feedback is doen most of the time by monitoring the 5V output because the logic circuits require good steady 5V to run properly, the 13/16V for the backlights inverter circuit does not require regulated voltage to run.
The green fuse is fed by the B+ (13~16V) power supply to run the backlights circuit. See pictures in post 10. Since there is no load on the 13-16V line, the volage will be higher until the inverter circuits are running.

[Davi.p]

Re: Samsung 2253LW

i understand very few, why don't you post the voltage readings on the output connector? is the double diode ok? Is the main mosfet on primary ok? Where is the green fuse resistor?

[budm]

Re: Samsung 2253LW

Since you are reading 16V instead of 13v, what do you read on the 5V out put?

[jahjhai]

Re: Samsung 2253LW

@budm, i'll give it a try anyways, can you provide me some voltage reading on the MBR20100CT, its hard to guess with the correct voltages for this power supply, im kinda lost since i dont have schematic diagram for this.,

by the way i got some concern with the supply voltage for the 13V, i checked the voltage on it and gives me a 16V reading.. were should i start checking and also the other component with the 6pins, im not sure if that also is damage..

thanks in advance
happy holidays to everyone...

[budm]

Re: Samsung 2253LW

@JAHJHI: leave that green fuse out off the circuits, then power up the power supply board by itself and see if you are getting any voltages on those caps you have replaced, if you do, then the MBR20100CT is not the problem.
Does the MBR20100 checked out as shorted out?
https://cdn.badcaps-static.com/pdfs/...d01a5d055f.pdf

[jahjhai]

Re: Samsung 2253LW

greetings everyone...

i manage to replace the fuse resistor and happens to check and suspect that the mbr20100ct which is a switch mode power rectifiers could be faulty. i am not aware about the proper voltage data on these components and needs assistance from everyone, since i dont have any clue on what will be their voltage reading. if only i have a schematic diagram for the mckinley 22 power supply of the 2253lw samsung monitor i can fix this with no problem at all..

regards to everyone out there...

[budm]

Re: Samsung 2253LW

That green fuse is for feeding the B+ to the inverter circuits, so if is blown then more likely that you do have shorted out MOSFETs that drive the Inverter transformer.
Need to get the P/N of the SMD Mosfets to get the pin out then check for low resistance readings between S and D pins of the MOSFET.

[selldoor]

Re: Samsung 2253LW

and oh by the way I used 1000uF/25V since its hard to find 820uF here.. will that hurt the power supply??

That is ok you are safe to go one step higher. Low ESR would be good but I guess you have to use what you can get.

If the Fuse you mention is in the circuit to power the back lights then obviously they will not come on. This may also distort some readings on other voltages

[jahjhai]

Re: Samsung 2253LW

yes the same problem..

did check some critical components... like the fuse resistor which i believe is open since there is no continuity.

i did replace the caps also same problem with ab101

[jahjhai]

Re: Samsung 2253LW

best thing is provide some test points were in i can compare the voltage data for each critical components.. one of my observation is that the 13.0V gives me 16V which is for the LCD video controller area. im not sure if there is problem on that part. tomorrow i'll do a lot of testing and check the flow of each voltage pathway..

and oh by the way I used 1000uF/25V since its hard to find 820uF here.. will that hurt the power supply??

[jahjhai]

Re: Samsung 2253LW

yup i just did replaced the 820uF/25V caps near the output area for the ccfl, high pitch noise is heard and tested some components, problem is the green fuse resistor has no continuity using the tester with beep continuity.. trying to find out if the mbr20100ct is bad, led indicates power which is the blue led. almost the same problem with ab101

[budm]

Re: Samsung 2253LW

@JAHJHAI: Does your board have bad caps as shown by ab101?

[jahjhai]

Re: Samsung 2253LW

ab101 what was your conclusion and findings? were you able to fix the problem,. i got the same problem that is why im asking about this problem.. if your able to fix it it would be of great help... thanks in advance..

[ab101]

Re: Samsung 2253LW

OK going to try and replace all other caps except the big one - will report back.

thanks for the help!

[selldoor]

Re: Samsung 2253LW

Sam young caps do not have a great reputation.
Without a meter it is pointless to continue £3 on ebay - not brilliant but
would suffice for a one off job. ( Been using my similar for years)
http://www.ebay.co.uk/itm/Digital-Vo...item3a73e80494

You cannot tell how good caps are by looking.

These caps are all same make , a similar age, in a similar situation. How long do you think before they need replacing? - Ignore the big one - its situation is a bit different.

Cheesy analogy - Buy 6 packs of cheese at the same time, same use by date (two weeks ago) all kept in same place in fridge you notice one has gone off. The other five LOOK ok - How long for? eat it - I dont think so.

[ab101]

Re: Samsung 2253LW

board markings are

B-DIM
13.0v
GND
GND
5.1V
5.1V
A-DIM
on/off
3.3v
LED
KEY1
KEY2