Samsung 912N Problem

[LAS]

Re: Samsung 912N Problem

Perhaps something here: on post #1, the heatsink on the bottom of the left hand photo is energized with about 70v. Is this normal?

[LAS]

Re: Samsung 912N Problem

Front and back of the logic board:

[LAS]

Re: Samsung 912N Problem

Thank you for your response retiredcaps. Those are good questions and I will answer them this holiday weekend. As to Nothing, the screen goes dark, ie the backlights switch off. Blue power light also goes out at that time too. Then I unplug the VGA cable and then I can turn it back on again and get the screen saver. And I have tried a couple different VGA cables. And I will post logic board photos as well.

[retiredcaps]

Re: Samsung 912N Problem

The screen saver, however, does go out as soon as I plug in the signal cable. And then I get nothing.

What do you mean by nothing?

1) What color is the power LED when nothing happens?

2) If you shine a flashlight on the screen, can you see your desktop?

3) Are the backlights on or off during nothing?

4) Is the screen white or black during nothing?

5) Have you tried a different VGA cable?

[retiredcaps]

Re: Samsung 912N Problem

Post a picture of the logic/main board.

[LAS]

Re: Samsung 912N Problem

So Digikey arrived today, and all caps have been replaced, but my monitor is still up to its same old tricks. The good news, however, is that I am getting quite procifient at changing caps, and can now do it in record time, and the board looks cleaner than ever too. Too bad it didn't fix the problem though.

I have attached a photo of the 'Check Signal Cable' screen saver that comes up as soon as I power on the monitor with no cable attached. It shifts all over the monitor every few minutes, so the ccfls are working, and not shutting down, but the rectangle doesn't look quite right. Has anyone ever seen a Samsung screen saver look this odd before?

I'm also thinking I don't have the '2 seconds to black' phenomenon. The screen saver, however, does go out as soon as I plug in the signal cable. And then I get nothing.

So at this time I once again appeal to the collective wisdom to ask if anyone has ever seen such a situation before.

Thanks all.

[LAS]

Re: Samsung 912N Problem

A little OT, but last week I bought some capacitors for my guitar amplifier from Newark element14, and since it was my first purchase, they emailed me with a 15% off voucher code to either use or share with friends. I would rather not post it onto the internet, but have no problems passing long in a PM if anyone would like it. It can be used multiple times until 4/30.

[LAS]

Re: Samsung 912N Problem

Project on hold for a few days while I salvage some ccfls from a broken monitor at work...

A minor problem is at hand, and I am hoping some BadCaps person can help. I have dissected a dead Dell monitor so I can use the ccfl for testing in my Samsung, but I immediately saw that the Dell connectors are different.

Does anyone have an unwanted bad Samsung ccfl wire and connector? If I can get ahold of one, then I can cut the Dell wires and splice on the Samsung wires.

I have a PayPal account and would gladly send $ for postage and whatever you think it is worth. I live in California.

PM me if you can help. Thanks.

[vinceroger69]

Re: Samsung 912N Problem

thanks for the link will have to invest in a esr meter then or build one.

[retiredcaps]

Re: Samsung 912N Problem

A cap can still be within its capacitance tolerance, but be totally out on ESR.

Here is evidence from my fellow Canadian smason ...

https://www.badcaps.net/forum/showth...on+newbies+esr

[vinceroger69]

Re: Samsung 912N Problem

QUOTE retiredcaps post
I reuse unbloated old caps if they measure up to their capacitance for side projects. I don't have an ESR meter though.

sorry for hijacking the thread i also dont have a esr meter but have a good vc6013 capacitance meter which i use
http://www.victorelectronics.com/spe...6013_specs.htm
so as long as there are within in correct uf etc ranges with no signs of bulging etc they should still be ok to re use in other projects and if still in use and read the correct capacitence they should be ok?

[retiredcaps]

Re: Samsung 912N Problem

I figure that the caps should be done anyhow, as long as it is apart and may indeed be the problem. $7 from DigiKey, all in, is a true bargain.

Save the old Samxon GF caps. They may come in handy for other projects where you need to stick in a cap for testing purposes.

I reuse unbloated old caps if they measure up to their capacitance for side projects. I don't have an ESR meter though.

For example, I have a couple of no name ATX power supplies that have bloated caps. I would never use them in a system and I would recap them with used caps and use them as a variable power supply for testing purposes.

$7 doesn't even cover the shipping costs to Canada ($8 s/h).

[LAS]

Re: Samsung 912N Problem

Project on hold for a few days while I salvage some ccfls from a broken monitor at work, and also for my caps to arrive. I figure that the caps should be done anyhow, as long as it is apart and may indeed be the problem. $7 from DigiKey, all in, is a true bargain.

I'll post next week after I move forward. Thanks again all.

[Jasgriff]

Re: Samsung 912N Problem

Same as retired caps comment..... I would also say if you have more than 1 spare ccfl then bring that test also. I have pent a few wasted hours looking for other faults when in fact I had 2 broken ccfl cables

[retiredcaps]

Re: Samsung 912N Problem

When only one ccfl is attached at a time, all lead to two seconds to black;

That is expected. The pwm inverter IC operates as "all or nothing". Either all ccfls work or none at all.

Testing one ccfl at a time only verifies that the ccfl itself isn't cracked or completely broken. The problem still could be that the ccfl is getting old and drawing too much currrent and/or the return wiring is internally frayed.

The only way to completely rule out the ccfls is to use a good spare one.

[LAS]

Re: Samsung 912N Problem

<<<2) What is the part number of T602 and T603?>>
TMP90199CT
0424E

I also have been able to verify that each tube lights up briefly when only one is plugged in at a time, ie I get two seconds to black with each one in turn.

An interesting observation is that the roving 'Check Signal Cable' rectangle is not uniform along its edges.

I have also measured 156 volts across the large cap.

Sounds like it might be time to order the caps unless anything in this comment leads anyone to think of anything else to check.

So, to recap (ha ha, no pun intended)
When turned on with no video cable attached, I get the roving 'Check Signal' rectangle, but with erratic edges;
Attaching a video cable and computer leads to two seconds to black;
inverters check out ok;
When only one ccfl is attached at a time, all lead to two seconds to black;
Caps look ok but are all original Samxon;
The two round fuses have continuity (am I missing any others?)
Connectors have been reseated;
155v across the big cap.

New caps time?

Thanks all as always.

[LAS]

Re: Samsung 912N Problem

I had read earlier about the use of an 1157 auto bulb - but I was mistaken. I have a spare ccfl bulb available at my office, and I can fully test it Monday.

In the meantime, I keep thinking about how I don't get the two seconds to black when there is no video cable attached. Makes me think it might indeed be a caps problem.

[Jasgriff]

Re: Samsung 912N Problem

I'm sure you don't mean to replace the ccfl with a low voltage bulb? The ccfl runs at a much higher voltage and a normal bulb would just blow.

[retiredcaps]

Re: Samsung 912N Problem

Am I able to substitute an 1157 auto bulb in place of a ccfl?

I'm thinking this monitor may have been dropped, as the base is broken where it is secured to the monitor with the four screws.

I never tried with an auto bulb.

If the monitor has been dropped, then you may have a broken ccfl?

You can try the test in post #20 section 5b.

[LAS]

Re: Samsung 912N Problem

Also - I only get the two seconds to black after the video cable is attached. Maybe low voltages due to bad caps?