Samsung PN50C450B1D

[johns1mj]

OK I have a plasma tv pn50c450 that has sound but no picture.
Tested the power supply with all boards connected, X SUS removed, Y buffer removed but x connected, and y buffer and x sus disconnected. on all 4 tests the Vs was between 203 and 205, 205 was on sticker. The Va was almost a solid 53 every time, 55 on sticker. The Vsc was supposed to be -178.
All -90
-x -83
-y buffer -101
-y buf -x -92
The Ve was supposed to be 83. I never got a solid reading. It would jump from -300 to 50 and back and forth. Also on the tag there is a 2Ve reading of 71. I could not find the 2Ve test point. I assumed this was for a different model.
I performed the quick test on the Y-buffer. Both middle connectors are shorted together on all pins.
After all this I conclude the Y-sus board is bad and the Y-buffer is bad. The X boards will need to be tested once Working y boards are installed.

Does this follow? Did I miss a step?

[ozzy214]

Re: Samsung PN50C450B1D

Theres a 99% chance buffer still good, but y sus bad. Look for pits and craters in the i/c chips on the buffer. If none. Then install y sustain and cross your fingers. I have heard of cases where buffer takes out new y sustain, but I tend to think of it as a old wives tale. I fixed 5 plasmas last 3 months. I didnt replace a buffer on any of them. Just y sustain and done!

[rccrasher65]

Re: Samsung PN50C450B1D

I have boards for this set, no y main though!

[ReeceyBurger123]

Re: Samsung PN50C450B1D

Ysus and Xsus are chained recovery in this set so bad Y can kill X and reverse, test all the main Igbt transistors on both the Y and Xmain they are on the heatsinks and surface mounted on the bottom side.

[johns1mj]

Re: Samsung PN50C450B1D

I have boards for this set, no y main though!

I may get ahold of you for boards.

[johns1mj]

Re: Samsung PN50C450B1D

Ysus and Xsus are chained recovery in this set so bad Y can kill X and reverse, test all the main Igbt transistors on both the Y and Xmain they are on the heatsinks and surface mounted on the bottom side.

For testing purposes is there a difference between mosfet and a igbt?

[ReeceyBurger123]

Re: Samsung PN50C450B1D

Have a read of this buddy, mosfets and IGBTS can be test in the same way though with a multimeter in diode mode.

http://www.differencebetween.com/dif...and-vs-mosfet/

[johns1mj]

Re: Samsung PN50C450B1D

OK, a used y-sus just arrived. The y-sus is running -196 tag says -178. I do not find a variance listed anywhere. Is this to far out?

[johns1mj]

Re: Samsung PN50C450B1D

Ok, decided to try it.
VS 203 205 sticker
Va 53 55 sticker
Vsc -198 -178 sticker
Ve 85 83 sticker
I get a flash of light and then no picture and no back lights. I still have sound. The voltages then begin to drop.
What next?

[dick_barton]

Re: Samsung PN50C450B1D

There are generally a few pots on the Ysus board for adjustment. Is there one for Vsc?

[johns1mj]

Re: Samsung PN50C450B1D

The 3 adjustable pots all say VR- scan fr and rr. The board power up for 7 seconds and then drops.

[dick_barton]

Re: Samsung PN50C450B1D

I think VR_VSCAN is Vsc but perhaps someone can confirm this before you alter it.

[ReeceyBurger123]

Re: Samsung PN50C450B1D

Yes adjust V-Vsc while monitoring the Vsc voltage. Might be best to keep it a couple volts higher as it will help remove any mal discharge in the screen quicker.

[johns1mj]

Re: Samsung PN50C450B1D

I adjusted the Vsc to -180. I have removed all connectors but the power supply to the y-sus. The board holds power steady. I connected the y-buffer and tested, holding power steady. hooked up the x board Ve was down to 70, adjusted to 78(83 sticker). I do not have the lower boards that are attached to the screen hooked to the logic. The voltage dropped after 7 seconds. I attached all boards and the same happened. I removed the ribbon between the logic and the y-sus. Everything checked normal voltage wise. However, I did not get the back light flash like when the logic was hooked up. The green light is flashing once a second on the logic board. disconnect all ribbons but the y-sus to the logic board and same results, light one second off and 4 seconds on.
This leads me to believe I also have a bad logic board. Did a quick check for shorts and didn't fine any.
Any advice for testing before I order a logic board?

[rccrasher65]

Re: Samsung PN50C450B1D

Send me Pm. I have new logic board, Xmain, and main board.

[ReeceyBurger123]

Re: Samsung PN50C450B1D

So what happens if you disconnect the Ysus or Xsus power do the voltages stay ?

[johns1mj]

Re: Samsung PN50C450B1D

Voltages only drop if tcon is connected to the ysus

[tvsteve2]

Re: Samsung PN50C450B1D

You mean Control board as Plasmas DON'T have T-cons!

[johns1mj]

Re: Samsung PN50C450B1D

Technically Samsung named it a logic board.

[rccrasher65]

Re: Samsung PN50C450B1D

Is this the board you need? main logic board.