Samsung 204B LCD has slow refresh, even after recapping

[PaperEngineer]

Hi,

I just replaced 5 capacitors (three 330uF 25V, two 820uF 25V, skipped the 47uF 50V since it looked ok and seemed harder to replace) on the power supply in a Samsung 204B LCD monitor. The screen still displays vertical lines and is very slow to refresh: the cursor shows the trail of where it has been and windows stay on screen even after they're closed.

Has anyone heard of this? I'm open to ideas.

Thanks.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

I just replaced 5 capacitors (three 330uF 25V, two 820uF 25V, skipped the 47uF 50V since it looked ok and seemed harder to replace) on the power supply in a Samsung 204B LCD monitor.

1) The 47uF 50V cap is an important cap (i.e. startup cap) and must be replaced if you want to monitor to last. Use something like (to support this site)

https://www.badcaps.net/store/produc...roducts_id=179

or

http://www.digikey.com/product-detai...0321-ND/266330

2) Post clear focused top down pictures of all your boards following my sig file below exactly. We want the picture compositions like so

https://www.badcaps.net/forum/showpo...94&postcount=1

3) Do you have a multimeter and know how to measure DC voltage? The problem may lie with a bad voltage regulator on the logic board.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

Thanks for the fast reply.

1) The 47uF 50V cap is an important cap (i.e. startup cap) and must be replaced if you want to monitor to last. Use something like (to support this site)

https://www.badcaps.net/store/produc...roducts_id=179

or

http://www.digikey.com/product-detai...0321-ND/266330

Thanks, I've already obtained the part locally. At any rate, from what I read, it sounds like it would not cause the symptoms that I'm seeing?

2) Post clear focused top down pictures of all your boards following my sig file below exactly. We want the picture compositions like so

https://www.badcaps.net/forum/showpo...94&postcount=1

Ok, I will take the pictures tomorrow in the daytime.

3) Do you have a multimeter and know how to measure DC voltage? The problem may lie with a bad voltage regulator on the logic board.

I haven't done this recently, but I'm guessing that it would require measuring while the device is plugged in and powered? That is something that I'm reluctant to do, being a newbie. Let me know if it's the only course of action and I will reconsider.

Thanks again, I'll get those pics tomorrow.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

I haven't done this recently, but I'm guessing that it would require measuring while the device is plugged in and powered? That is something that I'm reluctant to do, being a newbie. Let me know if it's the only course of action and I will reconsider.

Taking DC voltage readings will require the lcd to be plugged in and powered on.

The voltage readings that you will be taking are less than 5V DC (less than your standard 9V battery) on the logic board. No readings are required from the power board. If you don't touch the power board, you will be fine.

If you are worried about getting shocked, you should know that when you recapped the power supply, the largest capacitor MAY have been charged to 165V or 380V DC.

Most modern lcds have a bleeder resistor that discharges the largest capacitor in a few minutes, but as I discovered in a LG 22 inch 2009 made monitor, that is NOT always the case. This largest capacitor held its full charge (165V DC) overnight and would have indefinitely until I discharged it.

In addition, if a voltage regulator is bad on the logic board, then replacing it requires a soldering iron, solder, etc. If you don't have these tools and are hesitant about taking the voltage reading, then you might as well look for a replacement board on ebay.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

Attached are the pictures. Thanks.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

You have 2 voltage regulators. If you want to measure the DC voltage, then

1) Set your multimeter (if manual range) to 20V DC.

2) Put your black probe on a ground screw (circled in black). Leave it there the entire time. This is your ground.

3) Put your red probe on each of the pins including the "cut" pin, but ignore the "fat" tab.

4) You should have 3 readings per regulator.

5) Report them like so along with the part number of the IC.

U100
AS1117-33
pin 1 = 0.0
pin 2 = 3.3
pin 3 = 5.0

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

Thanks, I've already obtained the part locally. At any rate, from what I read, it sounds like it would not cause the symptoms that I'm seeing?

Though unlikely, it possibly can. If the startup cap voltage is fluctuating, it may cause unstable voltage on the logic board.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

retiredcaps, thanks for the fast reply (and marking up my picture, wow!).

Let me see if I can recap the 47uF 50V capacitor. If that doesn't work, I'll try to get the voltages you suggested and reply back.

BTW, my problem sounds somewhat similar to this thread, though I'm not having exactly the same symptoms.

BTW2, I wondered if I was having the "tab bond" issue, but it doesn't seem to be that.

I'll be back. Thanks.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

Make sure you read post #4. It got in before your picture post and you may have missed it.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

Make sure you read post #4. It got in before your picture post and you may have missed it.

Thanks, yeah, I saw it. I actually didn't recap the 450V capacitor since most repair kits didn't include it and based on an old post of yours. So I was pretty careful not to mess with it when recapping the others.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

Other suggestions include

a) cleaning and reseating every cable whether you touched it or not
b) trying another VGA or DVI cable
c) trying a different computer
d) doublecheck your OS refresh display settings
e) if the monitor supports it, set it back to factory defaults

[tom66]

Re: Samsung 204B LCD has slow refresh, even after recapping

It looks like a T-con problem - a loss of Voff or Von voltage.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

I recapped the 47uF 50V capacitor and there was no change, it still has the slow refresh, cursor trails, etc.

I tried reseating every cable, I tried another VGA cable, the problem occurs without a computer connected, and I also reset to factory defaults by holding [enter] for 5-10 sec in any menu. Still, no improvement.

What could cause a T-con problem? What is a T-con exactly? From searching the web, it sounds like it refers to the logic board... Is it fixable?

I haven't yet gotten the voltage regulator measurements -- I'm currently thinking, trying to decide what to do.

Thanks.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

What could cause a T-con problem? What is a T-con exactly? From searching the web, it sounds like it refers to the logic board... Is it fixable?

I haven't yet gotten the voltage regulator measurements -- I'm currently thinking, trying to decide what to do.

A t-con is board that is timing control. Measuring voltages on a t-con also requires power on.

No sense talking about taking measurements if you are not going to do them.

[PaperEngineer]

Re: Samsung 204B LCD has slow refresh, even after recapping

To close on this thread: I decided to call it quits for now and I bought a new monitor.

Thanks retiredcaps and tom66 for your time and energy.

[retiredcaps]

Re: Samsung 204B LCD has slow refresh, even after recapping

To close on this thread: I decided to call it quits for now and I bought a new monitor.

Sell, give away, or recycle your old one. Someone else will probably take a shot of repairing it.