Samsung T200 constant on-and-off

[spenki]

Hi everyone, seems I have a monitor with an attitude It's a Samsung SynchMaster T200 bought in 2009 but worked very little.

Symptoms are almost periodical (every 5 seconds) picture on off behaviour with the power led doing the same.

Here is the video youtube.

First repair made was replacing all 11 of electrolytic capacitors, picture stabilized for 3 - 4 hours and then the problem came back.

Made DC output voltage readings (stable through the whole on off cycle):
PIN -> VOLTAGE
1 -> 0
2 -> 17.5 //this one is way off
3 -> 0
4 -> 0
5 -> 5.15
6 -> 5.15
7 -> 0
8 -> 2.8
9 -> 3.3
10 -> 3
11 -> 3
12 -> 1.3

Thank You in advance for ideas/suggestions!

[1supertech]

Re: Samsung T200 constant on-and-off

Solder joints c203,c202,c204 doesn't look good looks like + side of tabs are gone.

[spenki]

Re: Samsung T200 constant on-and-off

looks like + side of tabs are gone

By this You mean, + side of electrolytic capacitors on solder joints c203,c202,c204? I'm afraid i don't understand the tabs part...

I will try to fix the solder joints today (with just adding more solder).

[1supertech]

Re: Samsung T200 constant on-and-off

Tab is the silver circle you solder the leg of the capacitor to. if tab comes off you can scratch part of the coating down to copper then solder the cap leg to the copper trace.

[spenki]

Re: Samsung T200 constant on-and-off

Tab is the silver circle you solder the leg of the capacitor to. if tab comes off you can scratch part of the coating down to copper then solder the cap leg to the copper trace.

Thank You for an explanation @1supertech, after removing the solder I've found that about a half of the tab remained so I reapplied the solder again covering more surface. Couldn't make myself do the "scratching" part, I'm afraid to damage the board to the point of no return. But if this is mandatory and a safety precaution I'll repeat the procedure.

After those repairs the problem remained - 5 seconds of stable picture and an instant switch off and back on.

Then I've re-flowed bigger solder joints on the board and all 5 pins of the power switch connector (CN202), also redid the "wide" solders near U2 & U3 square chips.

The picture is currently stable and has been like that for the last 5 hours, monitor was turned on immediately after re-flowing.

I've also included another picture of the back of power board for another inspection, please do not hesitate to point out any mayor soldering faults.

[spenki]

Re: Samsung T200 constant on-and-off

The picture is currently stable and has been like that for the last 5 hours, monitor was turned on immediately after re-flowing.

Unfortunately monitor has returned to previous behavior after being unplugged for 24 hours.

It's the same 5 second picture and quick reset but now it shows sporadic analog/digital connection search after several resets.

[1supertech]

Re: Samsung T200 constant on-and-off

Check for more solder cracks recap all capacitors Sam Young aren't the best reputation.
I use Panasonic FM,FR series.