Samsung HP-S4233 Picture going out

[TimT]

Tv turns on fine but the picture will go out( black screen) in a few seconds. sometime longer. when picture is out sound works fine. seems everything works fine except loosing the picture.

if I remove the fuse from the x-main the Tv stays on. put that fuse back in and pull the fuse from Y main " fuse closest to power board " it also stays on. I notice some pink color near center of screen.

and theres a slight humm from transformer located at top center of power board.

[tom66]

Re: Samsung HP-S4233 Picture going out

You notice pink colour when the X-main is removed or when it is functioning?
Test the Vs voltage while it is running and check if this drops out.
Also check if panel glows in dark while running.
And does a bright white picture (e.g. snow) cut out quicker than a dark image?

This is an interesting plasma display which doesn't use a power factor correction circuit; if those big caps on top left are failed it could cause this issue.

[TimT]

Re: Samsung HP-S4233 Picture going out

I only noticed the pink when there's a white screen. or perhaps a certain shade of gray.. other than that it's not noticeable. I did not notice any glow.

there are two Vs on the power board. the top one was 177.1v then when the picture went out it droped to 2.237v then I tried the second vs the TV ran for about 20 minutes and then it powered off and then power back on. it's done this a few times tonight. first time that it has done it. so the second Vs is at 178.5v I got the TV going right now waiting for the screen to go out with the volume still working to take another reading.

[tom66]

Re: Samsung HP-S4233 Picture going out

The Vs supplies are the same, just maybe have a little less resistance in one path. No problem.

177V is too low, the rating for this panel is on the sticker but looks to be Vs=197V. Try adjusting the VS-ADJ potentiometer and see if you can get it to go to 197V.

[TimT]

Re: Samsung HP-S4233 Picture going out

I got the Vs set. i noticed it's at 197v when first powered on then when the picture is on screen it drops to around 177v and it does fluctuate. today it's just running for a few seconds then picture drops out. I also noticed two of the large caps on power board has a slight bulge

[tom66]

Re: Samsung HP-S4233 Picture going out

Yeah, I have seen this before. Try using a bit of contact cleaner on the adjustment potentiometer and turn it back a few times. If that doesn't fix it, remove the power supply and inspect the solder joints on the large power transistors -- common fault with this model is the solder joints crack.

[TimT]

Re: Samsung HP-S4233 Picture going out

so the problem is the drop from 197v to about 177v? if I need to remove power board any percauction I need to take?

[tom66]

Re: Samsung HP-S4233 Picture going out

Yes, plasma panels are very sensitive, good picture only from about +/-5V of Vs rating, and nothing visible below about 150V. Just leave the board unplugged for 5 minutes before removing it so there is minimal chance of being shocked. Like most LCD TV power boards...

[TimT]

Re: Samsung HP-S4233 Picture going out

did not see any cracks but there was a " gray powder " see picture. I cleaned this off and heated up the joints. checked the voltage " remaining " in large caps. cluster of 4 at top left. if i remember correct 2 were at 300v and the bottom 2 were at 5v. put board back and it would run at 197v " fluctuate " even with picture on, but would drop back down near 180v then picture would go out but sound still working.

[tom66]

Re: Samsung HP-S4233 Picture going out

For all devices on the heatsinks on the primary side retouch the solder.

[TimT]

Re: Samsung HP-S4233 Picture going out

got that done but still no change.

[tom66]

Re: Samsung HP-S4233 Picture going out

OK, does Va drop as well?

[TimT]

Re: Samsung HP-S4233 Picture going out

va is steady 65.5v even when picture goes out.

[tom66]

Re: Samsung HP-S4233 Picture going out

OK, do you have a can of freeze spray available? (You can also use compressed air can -- simply invert it to get freeze spray.)

When it is beginning to malfunction cool these caps down. If Vs returns then replace them, they are the fault.

[TimT]

Re: Samsung HP-S4233 Picture going out

I don't have any free spray but could get some compressed air tomorrow. or are there any other kind of capacitors I could use in its place? also would freezing them be an option?

[TimT]

Re: Samsung HP-S4233 Picture going out

pick up some compressed air and froze the caps when voltage droped. still no change

[tom66]

Re: Samsung HP-S4233 Picture going out

Can you try just before it goes to see if it runs longer?

[TimT]

Re: Samsung HP-S4233 Picture going out

I tried before the voltage dropped. That did not seem to help

[tom66]

Re: Samsung HP-S4233 Picture going out

OK, let's try another thing. Set up TV with a dim picture (like no signal screen.) Does it run longer than e.g. on snow or with bright picture?

[TimT]

Re: Samsung HP-S4233 Picture going out

it seems to run fine with the " no signal screen ". but when a picture does comes on screen thats when it has the problem. also when a picture comes on thats when the transformers get a little noisy