Broken Samsung 2493HM - blinking LED

[budm]

Re: Broken Samsung 2493HM - blinking LED

That is going to be tough to trace out the PFC circuits then.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

Budm, I'm thinking it isn't. I looked no further when I saw that my board has two fuses next to the AC plug and the schematic only shows one.

[budm]

Re: Broken Samsung 2493HM - blinking LED

Notes:Please verify that the sch I posted matches your board.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

And yes, black cap is a Panasonic FR series.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

Thanks retiredcaps. The next couple of days are pretty hectic but should be able to investigate all of the above Saturday.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Looking at the back of the pcb, I notice there may be some solder crack rings in LP801S. As a longshot, you might want to reflow that entire PFC area with some fresh 60/40 solder on anything that looks remotely bad.

Anyway, that should be enough ideas for now.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Is that black cap just above the 00195A a Panasonic?

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

What is part number ICP801S? It is on the backside 8 pin IC.

Using the schematic that budm provided, ICP801S is TDA4863G which is the PFC IC as per

https://cdn.badcaps-static.com/pdfs/...17ea6ca5bc.pdf

Refer to figure 2 in the datasheet. Using pin 6 as ground, CAREFULLY report all the DCV readings for pins 1-8 wrt to pin 6 (GND). Any slip of the probe will cause

For stuff like this, I get my sharpest probes out and wear safety glasses.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Hmm, I failed to notice earlier that the power board is a BN44-00195A. There are several "usual suspects", I believe, for this board. I'll have to review the threads to see what they are.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

My guess is that BM801 is a bead from the picture? I'm not sure what the M stands for. A bead would measure around 0.1 ohms or less.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

Can identify what sort of device BM801 is? It is right next to the big 82uf cap on the power board. It is reading .2 ohms, about the same as the meter's probe resistance. Perhaps I'm back in the game??

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Datasheet is attached...can someone provide pointers on how I can test them?

You can see if pins are shorted using every possible combination.

In the PFC section, I think there has been a handful of cases where the 431 was bad causing the PFC not to work properly.

PS. I believe 431 = KIA431 = TL431.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

It looks like there are a fair amount of KIA431A diodes on the power board. Might be a good exercise to test them all.

Datasheet is attached...can someone provide pointers on how I can test them?

Thanks all.

[newbie1]

Re: Broken Samsung 2493HM - blinking LED

Long shot. How about removing TM801 from the board and check whether the 'glue' is still stuck on the board? I had previously had that ONCE. The 'glue' shorted the path of the pins below that TM801 and after removing (scraping) it, the monitor came back to live.

However, i am still having 3 of these board which i have given up trouble shooting. This is because all three of them are having TM801 'fused' (burnt). So i ended up buying the whole board but of compatible model. I am having nightmare whenever i receive this particular power board to repair.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Additionally, before you spend too much time and money trying to fix this monitor, try to see with a flashlight if the screen is cracked or broken. It would be a shame to get everything working only to find out the screen is cracked. Sometimes, the "flashlight trick" doesn't work and maybe some good old California sunshine might reveal more?

If the power supply is working via PS_ON (or we supply the 5V DC an 24V DC externally - though I'm not sure how to bypass the PFC), then "jumping" BL_ON (backlight on) will force the backlights on.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

If the main board is indeed bad due to a proprietary component (like IC300), then it is pretty much impossible to get a replacement part. Or if the eeprom/firmware is corrupt, then it would be difficult to reprogram?

You can trying tracing the PS_ON pin on the main board to see where the circuit path goes and check each component. The continuity feature on the Fluke 12B will help you track down which components are in the circuit.

It might be a transistor that is responsible for switching on PS_ON isn't working or shorted?

[jetadm123]

Re: Broken Samsung 2493HM - blinking LED

Looks like the voltage regulator output is correct. To summarize, the main board does not seem to output the 3V required for PS_ON. Even if it did, based on you applying the jumper to PS_ON without the PFC starting up, I would agree with retiredcaps that it appears you have problems with both the main board and power supply.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

F601 tested ok
IC113: 3.4v, 0v on the short leg, 2.5v.

I put the jumper back on to test just once more, with similar results. 5v on standby, 3v on pson, and 0v up on the 24v pin.

I'd believe multiple problems on this monitor. I wasn't the first to crack it open, and who knows what went on before it came to me.

In the meantime, thanks all for the suggestions.

[jetadm123]

Re: Broken Samsung 2493HM - blinking LED

Also, try checking fuse F601 at the top of your mainboard.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

You may have multiple problems.

1) Jumping 5V standby to PS_ON with main board disconnected should have brought up the other power supply rails. There may be a problem with the PFC section?

2) Getting a reading of between 0 and 1V DC on the PS_ON pin with the main board connected suggests there is something could be wrong with the main board. The main board, if working correctly, should be sending out > 3V DC (typically).

3) IC113 on the main board looks like a fixed 2.5V regulator. Measure the 3 pins (including the cut pin) with respect to ground. Report your readings.

4) Measuring the big cap and PFC section can involve DCV in the 400V range. BE CAREFUL.