Samsung Syncmaster 245BW

[Dyingsoul]

Re: Samsung Syncmaster 245BW

This is a DOUBLE POST !!

His bridge rectifier is hanging loose on the board and he doesnt seem to want to try and fix it
to see if that is cause of the buzz.

I dont know how to fix it. Instead of telling that "I dont want to fix it" you could tell me that how to fix it because i have no idea... Im afraid of breaking the circuit, thats why im not touching it and looking for advice.

[selldoor]

Re: Samsung Syncmaster 245BW

If you are not going to touch it you cant fix it so you might as well give up
- -I have.

[Dyingsoul]

Re: Samsung Syncmaster 245BW

You really cant understand? How else should I explain? I dont know what to do with it and I am looking for advice.

Anyway I see that you can't help me with it so I did it on my own. Took some photos of the result.

Also I made a new video to demonstrate the strange noise coming out of the monitor.

http://www.youtube.com/watch?v=d4O8zvG4wTw

Anybody could help me beside selldoor?

[selldoor]

Re: Samsung Syncmaster 245BW

I dont know how to fix it. Instead of telling that "I dont want to fix it" you could tell me that how to fix it because i have no idea... Im afraid of breaking the circuit, thats why im not touching it and looking for advice.

What did you think this was, if not how to fix it?

https://www.badcaps.net/forum/showpo...5&postcount=27

If you didnt run double threads you would manage better.

[californiak]

Re: Samsung Syncmaster 245BW

First of all thank you all for posting and thank you operators of this site... marvelous job everyone... I have 3 of these 245BWs with 173A PS, one stopped working with same symptoms as OP described... I changed all the caps, except the big one, and the 3 resistors as described by some of you and no success.... so I took it apart again removed all the caps, except the big one, LOL and measured the values, they all checked fine on the plus side (slightly over posted values)... then I checked the big cahuna CP803 82uP 450V and it read low so I removed it and measured again, showed 71uF so I figured that could be it...

ordered new one and while waiting I looked closely on the PCB around the area of the CP803 an noticed some gray traces coming from under the RM801... measured it and it is blown open... had I not removed the big CP803 I could not see the damage so I got lucky by being persistent... that area between the resistor and big cap is impossible to see without removing the resistor or the cap... attaching photos of the area... and the hidden damage... the resistor looked fine from the top, only after removing it you can see the blowout... LOL

I do have a questions however, this .22 ohm resistor is fusible? meaning it will blow to prevent more damage to surrounding components? function sort of like a fuse with assigned resistance? what should I replace it with if I can't find exact replacement, since I do not know the wattage? and what other components could have been damaged by the blowout if anyone knows? thank you

so as they say, you never know which little 50c part will fail, best to look real good all around and test as much as possible all the components, may save you a bit of time and headache in long run... good luck all...

[californiak]

Re: Samsung Syncmaster 245BW

Greeting everyone, seems I was a bit too optimistic while replacing damaged parts...

My monitor is 245BW, PS boars BN44-00173A is bad… replaced the 3 resistors and all caps including 82uF CP803 and the blown fusible resistor RM801 but when I plugged the monitor into outlet I heard a big pop and few small pops... RM801 .22ohm 1w resistor blew again.... what I need help with is - what other parts should I check to find the short thats causing the RM801 to blow...

I am not good at all reading the schematic diagrams... so if anyone has experience with how to trace the components and finding what parts are in line that need checking please let me know... I am good at some testing if guided properly and in replacing parts, just don't want to replace all parts, only the part(s) that is(are) shorted... or should I just buy a new(repaired) PS?... BTW, I read this thread and many others but could not find just the right answers...

I am attaching pictures, really could use help with this one

thanks

[budm]

Re: Samsung Syncmaster 245BW

Look for shorted out MOSFET inside ICM801.

[californiak]

Re: Samsung Syncmaster 245BW

Thank you budm, I will test it but I need to know few things:
right now I have the board out of monitor

1. can I test it without plugging in main board and inverter board or do I have to plug them in?
2. assuming power on (should I remove the RM801so it will not spark anymore before I connect the power in, I unplugged it when it started popping so ther may be some residual shorts)?
3. I need to know which pins to test and what to expect?

So would ICM 801 be the first in line to be possible cause or most likely one?

thanks again

[budm]

Re: Samsung Syncmaster 245BW

You do resistance testing without power applied or plugged in, we are looking for really low resistance reading in both direction of the probes.
Shorted ICM801 will be the most likely component that shorted out. If you remove the IC, the resistor will not be blowing up any more.
pin 19 & 23
pin 19 & 4
The pin out of this IC is little difficult to count since some of the pins are trimmed off.
RM803 (0.39 Ohms) connected to the pin 4 may be damaged also.

[californiak]

Re: Samsung Syncmaster 245BW

First 3 are trimmed off, correct?
Readings with ICM801 soldered to the board:

both 19-23 and 19-4 read very low resistance, I need to get better MM but its in the neighborhood of 0.1 to 0.3 ohms

same across RM803, somewhere around .2ohms

I have no 0 adjust on my cheap meter so it reads 1.2 ohms when I just touch the probes together... there is definitely some room for error +- few tents of ohm...

need to get better MM, will look for one today for sure

BTW CP803 that I replaced before the RM blew reads 73uF attached to the board so its still good I think?

Thanks

[budm]

Re: Samsung Syncmaster 245BW

Well, you do have shorted out MOSFET, need new module at least at this point.

[californiak]

Re: Samsung Syncmaster 245BW

Just ordered one on ebay, now I have to for it to get here...

Thank you budm, hope this will fix the problem... if not we'll take it to the next step...

[californiak]

Re: Samsung Syncmaster 245BW

One more question, should I order fusible resistor for the RM801 or is any .22ohm resistor considered fusible... markings are the same - Red Red Silver Gold...

thanks

[budm]

Re: Samsung Syncmaster 245BW

MOX (Metal Oxide) Flame proof power resistor can be used, when 0.22 Ohms connected across 380VDC due to shorted load, it will go open for sure without flame, so consider it as fusible, main key point is that it is flame proof.

[californiak]

Re: Samsung Syncmaster 245BW

Hello again, got the f9222L today and I am ready to replace it but... does anyone has a safe way to remove the old one without damaging the board... one leg at the time may not work too good on this one...

I have SAIKE SMD Rework Station with either hot air (temp + flow control) or soldering iron option (precision temp control)... was thinking using the hot air option on very low flow as not to disturb the adjacent components... anyone done it this way and can share some info would be appreciated... what temp solder is used on these boards? anyone knows?

don't have a tiny snips to just snip of the top side legs and then remove the stumps one by one, maybe this would be best? Maybe I should go and buy tiny snips...

[jetadm123]

Re: Samsung Syncmaster 245BW

I would say to try your rework station out on a scrap circuit board. That way, you can try different heat settings and get a better feel for using the unit itself. If you're new to repair, trying to learn how to use a new piece of hardware while trying to repair a circuit board at the same time is usually a bad combination.

Of course option B will work, but cutting all the leads will make the F9222L useless. That is, if the original was still good, this option will automatically make it bad.

Option C would be to use something like solder wick, which is essentially a braided copper wick that is used to soak up the molten solder.

[californiak]

Re: Samsung Syncmaster 245BW

I used option D, wiggled it until the legs broke off at the base of the chip and then desoldered them individually...

Brute force!!! LOL... but effective

I have experience with hot air desoldering (very tricky not to affect the surrounding components and/or ruin the board) some good, some bad...
Just didn't know what is the proper solder temperature for this particular board...

[jetadm123]

Re: Samsung Syncmaster 245BW

Ah, the "brute force" method! Just be careful though, too much pressure on those pins can transfer down to the copper pads they're soldered and can cause them to lift off the circuit board.

[californiak]

Re: Samsung Syncmaster 245BW

Finally had the chance to go back to fixing this thing, I checked the .39R 5w (RM803) resistor and it was good, soldered everything back in including new .22R 1w (RM801) and the F922L (ICM801S) and now I am ready to test it.

One question, can I just plug the PS board and turn it on independently from the other boards just to see if the RM801 will blow again or do I have to have the main and inverter connected to the PS board

And let me tell you, I am a bit scared to try it because if it blows again I may just go back to being an artist and leave this electronic stuff to you guys, and order rebuild one from china... LOL

[jetadm123]

Re: Samsung Syncmaster 245BW

Have you tried taking the same resistance measurements as you did in post #610?