Samsung PN58C550 Blank Screen with sound

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Unfortunately, I think you would need an oscilloscope to test the X-main and Y-main boards.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Thank you for all your help Tom66. I have replaced the X-main and Y-main boards with used ones with no change. So I think I’m down to deciding if I want to spend the money to have a pro tell me the TV is dead or repairable or just go buy a new one. I have narrowed it down to either a Panasonic or a LG both are mid level plasma’s with both of them having a good picture. Nether have any special features but my blue ray player does, and I have a good surround sound so all I want the TV to have is a great picture. Once again thank you for your help.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Panasonic is better. LG do produce decent plasmas, better than Samsung, but don't expect the same build quality as Panasonic. Especially as Panasonic are often price competitive with LG, I'd go for the Panasonic.

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

I have the PN58C550G1FXZA, with similar issues. The TV is less than three years old. I was watching my plasma and herd a fairly audible "pop" noise. Then a second later the screen went black. I mean black, no back light. I watched and executed the startup test from samsung on youtube and no self test started when I jumped pins 3 and 4 on the logic board and jumped the ps_on to ground. My logic board led flashes the top led once very quickly and then hold steady on the second led for 5 seconds on and 1 second off. I have replaced the power supply hoping a cheap and fast fix was in my future and same thing happens. I have been able to get the logic board top led to flash steady only when I have disconnected the Y board's ribbon cable from the logic board. That is the about inch wide cable that runs from the Y main straight to the logic board. Still no picture or backlight but I think maybe I have narrowed down the source? All my voltages stay good and steady when this ribbon cable is disconnected. Otherwise I have a brief good VS and VA voltages that quickly drop.

Any help would be great, and please let me know if I am looking in the wrong area for a troubleshoot. I have visually inspected my x main, y main, logic, and Main boards with no visible blown components or char marks. Caps all seem nice and hard with no swelling. My goal is to trace the bad component on the board and replace that. (I work with electrical engineers and would like to show then I have some skills

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

Here are my tv's parts:

From what I described above, can the failure be with any where else or with any other board other than the Y Main?

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

I found the bad part on the upper Y buffer. It was a resistor marked 470. Anyone know where this exact part is sold and the actual part number?
http://screencast.com/t/RGkQx9H0ps

[capkid]

Re: Samsung PN58C550 Blank Screen with sound

I found the bad part on the upper Y buffer. It was a resistor marked 470. Anyone know where this exact part is sold and the actual part number?
http://screencast.com/t/RGkQx9H0ps

That's a 47 ohm resistor. You should be able to find it on mouser.com or digikey.com. You'll need to measure the length and width to determine the correct size (normally in millimeters or inches). You could solder on a through-hole resistor; I'm guessing it's a 1/2-watt resistor, but you may want to go with a larger wattage resistor just in case.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

If that resistor is bad, it is likely the buffer chip near it is bad, or the panel is bad (shorted scan to sustain electrode) though the last is quite rare.

[capkid]

Re: Samsung PN58C550 Blank Screen with sound

If that resistor is bad, it is likely the buffer chip near it is bad, or the panel is bad (shorted scan to sustain electrode) though the last is quite rare.

Yeah, I've never seen a resistor fail alone on a buffer board.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Here's what happens when ShopJimmy doesn't test a buffer board pulled from a cracked screen:
http://assets.shopjimmy.com/media/ca...16519a-top.jpg

(Burned 47 ohm resistors.)

[capkid]

Re: Samsung PN58C550 Blank Screen with sound

Here's what happens when ShopJimmy doesn't test a buffer board pulled from a cracked screen:
http://assets.shopjimmy.com/media/ca...16519a-top.jpg

(Burned 47 ohm resistors.)

Hmm. Thanks for the word of warning

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

After further inspection and peeling back the glue over the components, I noticed a current regulator at the very end of the board was blackened and blown. Where can I find the schematic for this board? I am going to have to replaced that component also!

[capkid]

Re: Samsung PN58C550 Blank Screen with sound

I doubt that you'll find a schematic for that particular board. Do any of your buffer chips have visible damage such as pinholes or small burns?

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

The chips all have the black heat sinks on them. Should i pry those off and check?

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

Ok here is a pic of what I have found. Can I easily get these parts? Does anyone know what they are exactly? Also one chip has two pin holes on the underside of the board.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

The diode will be a 1 amp, 300V or higher rated schottky or fast silicon. The capacitor I'm not sure, but if you have a capacitance meter you can measure the others in the same position (out of circuit), and then select any 300V or higher 1206 ceramic X5R/X7R/NP0/C0G capacitor of that capacitance or near abouts.

The unfilled holes are unlikely to be a fault, what is more likely is the buffer chip is bad. Can you provide a closer shot of the chip? (top side)

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

Attacher are the pics. I was not sure what the buffer chip is. Hopefully it is in one of these:

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Buffer chips are the black/grey squares. Can we see a picture under this chip?

https://www.badcaps.net/forum/attach...2&d=1375288571

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

Here ya go! Any way to test the chips with the blown cap and diode? Please let me know what the verdict is and if I should just buy a new upper board.

[bucash]

Re: Samsung PN58C550 Blank Screen with sound

Any thoughts my friends? I am getting antsy to fix this or buy a new board? Thanks!