Broken Samsung 2493HM - blinking LED

[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.

[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?

[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.

[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.

[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.

[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

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

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.

[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

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

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

[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.

[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.

[LAS]

Re: Broken Samsung 2493HM - blinking LED

And yes, black cap is a Panasonic FR series.

[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

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

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

[LAS]

Re: Broken Samsung 2493HM - blinking LED

A quick question about ICP801S...mine has no marking on it whatsoever. Is the ground pin on the top row, second from the right? I'm thinking of soldering a wire to the ground and then clip onto it to simplify voltage measurements.

My chip looks like it became hot once upon a time.

[retiredcaps]

Re: Broken Samsung 2493HM - blinking LED

Is the ground pin on the top row, second from the right? I'm thinking of soldering a wire to the ground and then clip onto it to simplify voltage measurements.

I can't tell from the photo where the notch is to indicate pin 1 (see datasheet, figure 2). I also neglected to mention, as I always usually do, that the negative leg of the big capacitor is also your hot side ground. Therefore, if you measure the resistance of the negative big cap to pin 6 of the IC, it should read around 0.2 ohms.

When I measure high voltage I like to use aligator clips so I can probe using only one hand. Unfortunately on this board, the big filter cap is not laying down on its side like most so you cannot clip onto the negative cap leg. If you solder a wire, solder it onto the negative leg of the big filter capacitor.

One other test you can do before getting the DC voltage measurements is to measure the resistance between pin 8 (VCC) and pin 6 (GND). Report your reading. If it is shorted, remove the IC and see if it is shorted out of circuit and measure the resistance of the pcb pads.

[euromatlox]

Re: Broken Samsung 2493HM - blinking LED

For power board BN44-00195A you will probably need some smd components: 100ohm resistor, BZX84C27 zener diode, MMBT2222A transistor. Possibly also Sanken 8008hfe buck regulator, you can easily see if 8008hfe is ok by measuring ohms on the component legs. I have also read somewhere, that replacing 12nF/630v capacitor has helped.

More info is available in the forum:

https://www.badcaps.net/forum/showthread.php?t=18966

Easiest way, if possible and cost not too much, is to get Samsung 245b power board, BN44-00173A. It's much better board, usually easily fixed by just replacing caps and three 68ohm resistors.

I tried to repair BN44-00195A, got it to work somehow but soon problems begun again. That board had a broken 8008hfe, so it might be a bit more damaged than usual. I remember that 24v line showed 22.3v or something when I last measured it. I decided just to use BN44-00173A instead, and it works perfectly on Samsung 245b plus (only difference to 245b is different design inverter board).