Samsung Syncmaster 244T - fixed but not.

[Erwin0265]

Hi all,
OK, I'll be honest, I registered to get help with my monitor......
A few days ago, it started flickering (and, from what I have been able to ascertain from numerous searches; this is a rather common problem. However, mine ends with a little twist...).
I discovered after about 5 minutes of searching online that the probable culprit was bad caps (so now I'm finally on the right site... hopefully).
Anyway, I found this nicely written PDF file that had 6 pages that pretty much told me to replace capacitors C110 and C111. So I ordered a few of these capacitors online, waited til they arrived and then disassembled the monitor to discover mine was different (the guide described 2 x 820uF & 25V capacitors; mine had 3 x 1000uF & 35V).
So I decided to go to my local (32 km away) electronics store and purchased 4 x Brand:- S.I., 1000uF, 35V, 105ᵒC, Low ESR capacitors; the original capacitors were Brand:- CapXon, 1000uF, 35V, 105ᵒC capacitors (I purchased 4 rather than 3 in case of the inevitable F.U.).
Whist at the electronics store, the guy who served me pointed out that the large capacitor was also bulging slightly at the top; so I purchased a replacement for that one also.
Large Capacitor
Brand of original capacitor:- CapXon, 100 uF, 450V (GL108ᵒC, C630, VENT was written on the other side of the capacitor). The replacement I purchased is shown in one of the attached photos (sorry, my eyes can't read it now that it's installed). One thing I did notice was that the replacement was rated at 400V whilst the original was rated at 450V; which has me a bit confused as to whether I was sold a suitable component........

After replacing these capacitors and reassembling the monitor; to my absolute delight (and slight amazement as I had never done this sort of work before); the monitor was working and no longer flickering!
The repair lasted for 7 minutes and then the screen went black. I could turn the monitor off, leave for 10 seconds or so and then turn it back on to have it work for another 7 minutes.
So, yeah, I've "fixed" one problem but now I have another..........
Any suggestions as to what I did wrong?
Just one last point; the replacement capacitors (except for the large one) are physically larger than the originals and 2 sit hard up against each other so I placed a "pad" of folded up insulation tape inbetween the two touching capacitors (as seen in " Smaller Caps replaced.jpg").
Thanks for taking the time to read all of this...........

[attainteddragon]

Re: Samsung Syncmaster 244T - fixed but not.

you really need to redo the soldering on the secondary caps. looks like you had some trace damage. just lightly scratch away a little bit of the coating to reveal the trace underneath, tin it and then resolder the caps back in.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

What are secondary caps (I am assuming that these are the smaller replacements. ie. all except for the big one?)?
What's the trace?
Sorry - but I'm totally oblivious to the terminology.
Thanks for responding, btw; appreciate it........

[attainteddragon]

Re: Samsung Syncmaster 244T - fixed but not.

do all 3 of the smaller caps, next to where the cap legs are, under the green surface, you will have more copper tracks to work with. you are lucky that you have lots of area to play with on this board. if you don't have enough leg length, you can extend the legs with a little piece of wire, but i think you should be ok with what you have.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

OK, I'll give it another go - think I'll dig out my magnifying light. My eyes aren't what they used to be.
I'll report back once I know more.
Thanks again.

[dskall]

Re: Samsung Syncmaster 244T - fixed but not.

Measure the voltage across the big cap and see what dc voltage it is. 400 v replacement is probably marginal

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

Hey, dskall,
I assume that I do this whilst the monitor is powered up?
I know I need to take care not to randomly touch any old thing on the board, but I'm not sure here; do I plug it in, unplug and then measure or leave it plugged in whilst measuring or measure without powering up at all (to measure what the cap is holding without having been discharged)?
As mentioned; I've never done this before.
Replacing boards, print-heads, belts and alike, I have done but going to the point of attempting to repair a PCB is a first......................

[dskall]

Re: Samsung Syncmaster 244T - fixed but not.

Measure across it while it is on. I suspect it has around 390vdc so a 400 v cap is not enough margin and is working at it's limits.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

That's something I was thinking; the 400V is not enough to replace the 450V that was there.
But is this a reasonable symptom of an "overworked" (?) capacitor? To work for a short time and then just stop, but not blow at all and be able to continue its "job" after a 30 second break.....
Either way; I'm bloody annoyed that I was sold a cap that wasn't the specs comparable to the original. If I understand correctly (?), it's OK if the Voltage is rated a bit higher (say 500V or so), but lower is unacceptable?
Thanks for your time and knowledge, btw..........

[attainteddragon]

Re: Samsung Syncmaster 244T - fixed but not.

just out of curiosity, where did you get them. looks like altronics stock to me.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

Jaycar Electronics (pretty much the largest electronics store network here); I'm in Australia...........

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

dskall,
I put the board back in, screwed in the earth screw, turned on the monitor, measured between the poles of the big cap and got nothing.
I tried several times (it's kinda nerve racking as I'm trying not to touch anything else), on different settings (1000volt DC scale, 250, 50) and also tried reversing my multimeter probes as I couldn't remember which pole was negative, which positive; still nothing.
I'm wondering whether the cap has already shat itself; even though I still get the on screen message of "no signal detected, check input cable" (paraphrased) - it's not connected to a PC as it's in my workroom..............

[R_J]

Re: Samsung Syncmaster 244T - fixed but not.

If you get the "No Signal Detected" message then the power supply is working, like others mentioned, the soldering job on the caps you replaced is very bad and needs to be re-done also check that the copper traces where the caps are soldered are not torn, if they are you will need to repair them by scrapping some of the gren paint of the trace to expose the copper, then resolder the caps lead to it.
The connections circled in red are bad, You may need to add a wire as marked in green.
Also post a picture of the original large 450v cap. It may not be bad if its only the plastic top that is bulged and not the cap itself.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

The copper traces; are these the lines I marked in pink and does that mean all parts within that trace are electrically connected to each other?
Unfortunately, when I removed the large 450v cap, the pole came out of the cap before it came out of the circuitboard; so it's of no use.
Do you think it likely to be an issue or should I attempt a resolder of all replaced components and how things go?
I ask because you can only take one of these apart so many time before problems arise (Such as the plug that goes to the monitor's external controls which is only held in place by being squeezed between the screen and the front plastic bezel; this, and the fact that the video card and the power supply circuitboard lie loose on the back of the screen before the metal cover is replaced, which makes testing of the unit unassembled problematic. All I can think of is to tape pieces in place before testing; and returning the earth screw for the power supply circuitboard back where it belongs).
Another question; I was told to tin the wires coming out of each cap; I know how to tin a soldering iron, but how do you tin the capacitor wires? I think some new glasses may also help with this issue - I only realised the solder joints were so bad after you pointed it out and we had an enlarged photo to refer to..............

[kiko1]

Re: Samsung Syncmaster 244T - fixed but not.

Looking to PCB and doing some eye reverse engineering ...I would change 400V dcbus cap. to 450V soon as possible.
PS have PFC and is raising DCBUS voltage very close, or over 400V when you turn it on...That would be my first move.
Kristian

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

OK, I'm a total newbie to all of the terminology, let alone the acronyms...
DCBUS =
PS =
PFC =
For me, PC means post script, DCBUS is a bus that runs onm direct current; as for PFC - I only know of KFC..............

I understand that Jaycar sold me the wrong capacitor and as they are 40 odd kms away from me, I'd rather buy online than waste more fuel (I thought I'd go and see "the experts"; I was wrong).
Other than getting a 450V, 100uF Capacitor, what else should I be looking for (the original had GL108ᵒC, C630, VENT printed on the other side; is that relevant/important?).
This has become a learning experience for me now (I have a new replacement on its way to me by next Monday, hopefully); I only mention this to let people know there's no rush; I'm happy to take my time and hopefully learn something in the process (other than not all employees at Jaycar know what they are doing)............
Thanks to all for your time. I still need help - so please don't desert me.....

[R_J]

Re: Samsung Syncmaster 244T - fixed but not.

What you marked in pink is a copper circuit trace, under that thin green coating (paint) is the copper, If you use something like a small flat blade screwdriver, you can easily scrape away the green paint, exposing the copper and then solder to it if required.
I don't think that the positive (+) side of the 450 volt cap. is even making a connection to the trace, if its not that would explain why when you try and measure the voltage on the cap leads there was no voltage there.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

So you can still get a "No Signal Detected" message even if the large cap is not making proper contact in the circuit?
Also; how do you tin the capacitor wires?
I've gone online to an electronic company recommended on this forum (DigiKey) and ordered all of the capacitors again as well as a solder sucker and flux paste.
As this has become a learning activity, I want to really do it properly - even if it is a bit more expensive than originally planned.
But I wold still like to know about the cap wire tinning in the meantime. Thanks.

[Erwin0265]

Re: Samsung Syncmaster 244T - fixed but not.

I appear to have double-posted but I can't work out how to delete the second one.
Perhaps one of the "powers that be" can delete it?............

[attainteddragon]

Re: Samsung Syncmaster 244T - fixed but not.

tinning is just pre loading a lead, or pad, or whatever you are soldering, with some solder, to make sure that when you make your final connection, it all sticks together properly.