Samsung 226bw dead. No power

[selldoor]

Re: Samsung 226bw dead. No power

I have been reading this https://www.badcaps.net/forum/showthread.php?t=13149
Its a 223BW but seems to have the same main board.
Really only leads to more questions than answers.
One suggestion is that Q290 is some sort of reset controller but I dont know how you would test it.
Looking at your board Q401 looks a bit odd is it just the picture or has it been resoldered? does it need done again.

Next time its all connected up you could test and report the voltages on the test points on the back of the main board.


Finally more of a query for retiredcaps. If CN200 is the button board socket could they have used zero resistorsas fuses. R275 in particular I think seems to be in the area where on the back of the board it says LED_ GREEN.

[alexanna]

Re: Samsung 226bw dead. No power

Actually pin 9 is your on/off (see CN2). It should read over 3V when the lcd is on.

I may have missed something in one of the posts, but the monitor looks for on/off switch to momentarily change states to either turn the monitor on or off. IE: if the on/off pin normally has 3 volts it will toggle to 0 volts as long as the power switch is pressed, when the button is released it will go back to 3 volts.
So you will always read 3 volts unless the power button is pushed.

[retiredcaps]

Re: Samsung 226bw dead. No power

Pin 1 reads 0.18V and Pin 9 reads 3.38V in both states

Pin 9 (on/off) is "high" which is what I would expect when the lcd is turned on.

Pictures are attached. I'm not really sure how to measure the button. I took the grounded screw and measured the pins in the plug, which gave me a reading of 0 V.

Try this.

Plug in lcd. Put your black probe to a ground screw. Measure each color which pressing the on/off button. See if the voltage changes at all. On my test monitor, the on/off switch has 3.300V DC. When I press on/off, it drops momentarily to 0.029 and then goes to 3.290V DC.

[retiredcaps]

Re: Samsung 226bw dead. No power

I
Finally more of a query for retiredcaps. If CN200 is the button board socket could they have used zero resistorsas fuses. R275 in particular I think seems to be in the area where on the back of the board it says LED_ GREEN.

Wow, didn't even see page 3 of this until now.

My understanding of 0 ohm smd resistors is that they are used for the following:

1) place holder so that if something changes, they don't have to respin the pcb (oops, we need a 100 ohm resistor here for whatever reason)

2) it joins 2 different planes of the pcb (much like a jumper)

3) it is cheaper to use a 0 ohm smd resistor than a jumper wire because the automated machine can just be loaded up with one type of component versus multiple components

I don't ever recall seeing a 0 ohm resistor being used as a fuse. I know there are fusible resistors, but not usually in smd packages?

[retiredcaps]

Re: Samsung 226bw dead. No power

I may have missed something in one of the posts, but the monitor looks for on/off switch to momentarily change states to either turn the monitor on or off. IE: if the on/off pin normally has 3 volts it will toggle to 0 volts as long as the power switch is pressed, when the button is released it will go back to 3 volts.
So you will always read 3 volts unless the power button is pushed.

Again, I didn't even see page 3 until now. Yes, I realized after I posted my initial response it may have been confusing, but had to run off for a few hours before I could clarify as per post #43.

[selldoor]

Re: Samsung 226bw dead. No power

I don't ever recall seeing a 0 ohm resistor being used as a fuse. I know there are fusible resistors, but not usually in smd packages?

I only asked this as I raised a query regarding a 0 ohm resistor a few months back (having not seen one before) and 999999999 answered with:
Re: Zero Resistance resistor ?
No do not replace with a wire link. It could be acting as a mere jumper but 0 ohm resistors are often used as a form of cheap fuse. Given its dislodged state it is likely the fault caused an overcurrent condition which burnt the area and melted the solder joints (hard to tell exactly from the picture, with no info for all we know another person could have taken a soldering iron to it already) and if possible you should find the fault before applying power to the circuit as it "might" prevent further damage to do so.

At the time I checked what he said on the internet and from what I read was
happy that he was correct. Having said that I cannot quickly find the article
I read.

[enigmach]

Re: Samsung 226bw dead. No power

I´ve been a bit busy, but I just got round to measuring again.
With the power button, something weird seems to be going on. For starters, there was no proper grounding screw so I took the frame to which the button normally is grounded.
That aside, the voltages were very erratic. The only reading I got was on the one with the blue circle, which jumped around from 0 to 1.8V.

After this, I took the advice of measuring some testpoints on the back of the mainboard. The ones circled in red gave some odd readings and were typically off by at least 0.1 - 0.2 V from the specification. The further I got to the connector to the power button, the more the voltages seemed to drop.

My guess as to what the main issue is, is definitely the mainboard.
@selldoor: I haven't soldered on the logicboard/mainboard so it's at least the same for 3.5 years.

If you guys have some more suggestions to try I'm open to it, but it would appear that a new mainboard might be necessary.

Thanks for all the help so far

[retiredcaps]

Re: Samsung 226bw dead. No power

What are the DC voltages for CN200 (logic board)? You should have 4 readings.

[enigmach]

Re: Samsung 226bw dead. No power

what are the dc voltages for cn200 (logic board)? You should have 4 readings.

cn200
#1 : 0.01v
#2 : 1.82v
#3 : 1.83v
#4 : 1.82v

[enigmach]

Re: Samsung 226bw dead. No power

Any other tips on what I could try? I'm currently in doubt whether it's worth it to replace the logic board in a monitor that's been used quite intensively for 4.5 years, especially when it's uncertain if it'll fix the problem..

Thanks for your replies so far

[selldoor]

Re: Samsung 226bw dead. No power

Hi - running out of ideas here

Can you check a couple more parts on the main board Diodes D 701 D600 & D603
and Resistor R275. (Near CN200)
Then with it all connected up again can you check the voltages on the top of the main board where they are indicated
Should be 14 v on BD800
1v8 on C639
5 v on the pins on cn400

Please also check the voltage on each side of R275

[retiredcaps]

Re: Samsung 226bw dead. No power

One suggestion is that Q290 is some sort of reset controller but I dont know how you would test it.

If there is nothing left to try, you can try shorting out the two bottom pins to see if that causes the lcd to turn on. Use a screwdriver with a blade wide enough to touch both bottom pins.

[selldoor]

Re: Samsung 226bw dead. No power

Originally Posted by selldoor View Post
One suggestion is that Q290 is some sort of reset controller but I dont know how you would test it.

If there is nothing left to try, you can try shorting out the two bottom pins to see if that causes the lcd to turn on. Use a screwdriver with a blade wide enough to touch both bottom pins.

That should read U290 I got it wrong in my post -sorry no Q290 on the board.

There is another thread running where they are trying removing the reset controller - We can see how that turns out.

[enigmach]

Re: Samsung 226bw dead. No power

Hi - running out of ideas here

Can you check a couple more parts on the main board Diodes D 701 D600 & D603

D701: 2.5 kOhm
D600: 154 kOhm
D603: 142 kOhm

and Resistor R275. (Near CN200)

This one was hard to get a reading on: 1.4 kOhm

[QUOTE=selldoor;230136
Then with it all connected up again can you check the voltages on the top of the main board where they are indicated
Should be 14 v on BD800
1v8 on C639
5 v on the pins on cn400[/QUOTE]

I think you mean the BD600: 15.6 V
C639: 1.82V
The pins on CN400 read about 0.18V

Please also check the voltage on each side of R275

I couldn't get a Voltage over this..

Again, thanks for the suggestions

Would replacing the logic board be a good fix then? I've read that the CCFL could easily give me another year's worth of use out of it..

[selldoor]

Re: Samsung 226bw dead. No power

Diodes- You need to test in both directions should have a high resistance one way and low the other. Ideally To test properly you need to unsolder one end and lift slightly.This cuts out input from other components.

R275 That looks ok ( Its ok as long as it has measures more than 1 ohm.)

Yes I meant BD600

Clearly we are short of the 5v.

A new logic board might fix it - perhaps you can get one from somewhere that accepts returns if it doesnt work,then it will only cost the postage. If you do that perhaps you could still try the reset controller shorting with a screwdriver as a last ditch and let us know the result.
Sorry we couldnt fix it, you read of so many just changing the caps and its off then for some there just doesnt seem an answer.Still I suppose we have only tested a small percentage of the components on both boards.

[retiredcaps]

Re: Samsung 226bw dead. No power

If the screwdriver doesn't work, list the part numbers for IC202, IC603, IC203, IC201. For bonus points, provide the datasheet links.

[enigmach]

Re: Samsung 226bw dead. No power

Just wanted to pop in and say thanks. I ran out of time for troubleshooting, so I ordered a logic board which came in today. Except for a slight flicker and a short buzz the first cold start it seems to work fine now.

Thanks for all your help, I´m less afraid to repair my own electronics now

[sixstringartist]

Re: Samsung 226bw dead. No power

Hey all, Looks like some really good information in this thread. Unfortunately I am embarking on my own 226BW repair today. Would it be beneficial to use this thread since the previous two cases are resolved, or should I start a separate one?

[retiredcaps]

Re: Samsung 226bw dead. No power

Would it be beneficial to use this thread since the previous two cases are resolved, or should I start a separate one?

It doesn't matter. The regulars read all the threads (new or old).

Start by posting clear focused top down view pictures of all your boards following the instructions in my sig file in post #43 exactly.

[sixstringartist]

Re: Samsung 226bw dead. No power

Ok here it goes.

The story starts a couple years ago when my 226bw would not display anything. The blue light came on but just flashed. At the time it was within warranty so I shipped it in and it came back working, citing the power supply at the problem.

Fast forward to today. After having absolutely no issues with the monitor since, it flatlines on me. This time there is absolutely no indication of power. No blue light, no backlights, no display.

So I popped it open (pleasantly surprised at how easy it was to access), and immediately I see one slightly bulging cap (C113), but also there is some monstrosity on the back of the power board. It looks like some inline fixup possibly from when I RMA'd it (any insight into this would be greatly appreciated).

Ive taken some preliminary measurements but havent really encountered anything too suspect, yet.

Logic board ribbon (CN2)
1 - ON/OFF - 0V (Button board disconnected)
2 - A-DIM - 0V
3 - 13.5V - 14.45V
4 - 13.5V - 14.45V
5 - 13.5V - 14.45V
6 - GND - 0V
7 - GND - 0V
8 - GND - 0V
9 - B-DIM - 0V

Voltage Regulators (Logic Board)

IC602
D11 17-18
1. - GND - 0V
2. - OUT - 1.80V
3. - IN - 3.78V

IC204
6P 739 (not 738 as in previous posts)
1. ?? - 5.19V
2. GND? - 0V
3. ?? - 5.19V

IC601
17-33
1. GND - 0V
2. OUT - 3.32V
3. IN - 5.19V

IC702
1501-05
1. +13.5V - 14.45V
2. +5V - 5.17V
3. GND - 0V
4. +5V - 5.19V
5. GND - 0V

I thought the reading was strange on IC204 because I was expecting a vreg from reading this thread but it is a low voltage IR receiver.

I apologize for the photo quality but it is the best I can do for a whole board image with the equipment I have. I can take close-ups of subsections if necessary. Any layout or component location questions you're probably better off looking at the better quality images the previous posters have provided.

Feel free to not spend much time on this. I realize there is much else to do to trouble shoot the issue. This post is more for my personal benefit of record and future searchers than it is asking for advice (although any provided would be greatly appreciated). My next step will be to include the button board and rule out a bad switch.