Samsung plasma PN50C550G1F/ Sound, no picture

[rccrasher65]

Gentlemen, I have another Samsung Plasma (MY older Brother's) that I would like to save from the scrap heap. I started by turning on set. It has stand by red led on, plays a little tune for start up, sound comes on shortly after , but no video. Removed back and started checking every thing for visible damage, could not find any. I started checking the voltages on the power supply as per label. Va. 55v, Vs.211v, Vsc.-198v, and Ve.89v My readings were,Vs.9.75v, Va.3.6mv, Vsc.0v, could not find Ve voltage on board. I then checked CN802 to logic board. pin 1 05.3v, my reading 5.2v. pin 2 05.3v my reading 5.2v pins 3-4 are gnd. pin5- ps-on my reading was 0v, same with Vs-on, 0v . I then proceded to connector CN801 to main board Ps-on 0V , STBY 5.1V GRND 15v- my reading14.6 v All readings on this connector were ok except PS-on 0v. I started to disconnect one board at a time with no change to power supply voltages. I also did the test to main logic board, by shorting pins 3-4 to try and get test pattern, no luck. I'm thinking I'm stuck at this point, so any help would be appreciated on where to go from here. Pictures can be viewed on http://rccrasher65.imgur.com There are 10 pics in album. If you can't view please let me know, as I can still not load pics here for some reason, when I see everybody else having no problems. Its probably just me though. Thanks in advance for all the help. George

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

My main logic board has no blinking led lights also. Does anyone know where I can get the service or repair manual for this set. Thanks again,George

[martino]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

for test pattern,you need to unplug the big ribbon cables that goes to the mainboard as well as jumper pin 3-4.

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

You will also sometimes need to jumper PS ON signal to GND.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

for test pattern,you need to unplug the big ribbon cables that goes to the mainboard as well as jumper pin 3-4.

Martino , do you mean all of the ribbon cables going to logic main board, or just the LVDS cable.

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

In this case, it will only be the LVDS cable.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

You will also sometimes need to jumper PS ON signal to GND.

Tom, I have no PS-ON voltage, 0V On CN801 all voltage's check out, except PS-ON - 0V On CN802 i have 5.2V , 5.2V , gnd, gnd, PS-ON 0V, VS-ON 0V. On CN 804, both VS read 9.75V, they should be 211V, gnd, 15v reads 14.65V, gnd, VA. 3.5mv or 0V depending on what meter I use. one is autoranging, one is not. VA voltage should read 55V. VSC -198, and reads 0V, VE 89V could not find this on any board. I'll try test on main logic again, to see what happens. there are no led lit on this board. thanks again for all your help.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

In this case, it will only be the LVDS cable.

Tom, I did that the first time, only thing is pins are not marked, not sure what pins are 3-4. I did the bottom two looking straight at the tv, assuming pin 1 is at top left of board. I'm also using an alligator clip to short pins as they are too close together. should I try something different?

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

It's usually the top two pins. However you cannot cause any harm if they are in the wrong place - it will just switch to a different mode.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Ok, I will give that a try, how do you jumper PS-on, like you say. With the vs and va voltage's basically missing will this test work. I found a diode, giving me voltage in both directions.Its DB803 in center of PS. I also checked some fets, got OL on two on all pins, not very sure I'm doing this right but , if you could explain, I know I could do it. You can check these in circuit, can't you. My DVM is a klein MM200 ,auto ranging. I did some research on reading fets, but I still don't understand what setting to put meter on. In diode mode I can press the function key and read V or press again and read resistance, not sure what one to check fets in. Thanks again for all the help guys!

[jose6326]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

I have the same tv that I could not fix
I changed the psu, logic and x main boards

Tom even helped me test it with an o-scope
The only thing that I didn't replace wad the main board and the lower buffer boards

Hopefully you have better luck then I did

Here is my thread in case it might help

https://www.badcaps.net/forum/showthread.php?t=28943

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Thanks Jose, I did read through your thread, Why didn't you fix, was it not worth it, I don't want to throw money into this one, but I have a source for all new boards for it for $75.00, also I like to learn, so i'll try with everybody's help. My problem is a little different. I have no VA voltage, and only 9.75V on Vs. No pic, but sound. just hope it isn't the panel. Thanks for all your info. George

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

RC on the Logic board (pic4) right above the Samsung SD1 logo and arrow are 2 led's marked led2000 and led2001 with r2152 separating them. Led2000 should blink once per second when set is powered on, this indicates normal operation, once every 5 seconds indicates a fault.

I am currently trying to repair a pn60e550 set that has a different logic board than yours but has the same led2000 indicator but no led2001. When I first started T/Sing my set the led on mine would not blink, had to replace logic board.

Not sure yours has same problem as mine but just saying. I am fairly confident logic board controls VE and Vscan voltages but cannot confirm thru searching. VE voltage test point is usually on the X Main board, Vscan test point is usually found on Y Main board.

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Like Tom has indicated to get VS and Va volts on PSU to come up jumper PS-on to GND and VS-on to 5.3v. This is w/ both CN801 and CN802 cables unplugged from every thing.

If VS/VA volts don't come up or are unstable or low/high then it's safe to say PSU has a problem. The test points are indicted on the PSU

If VS/VA come on and are stable and close to panel sticker values then the problem lies elsewhere. You won't get VE or Vscan with X&Y boards unplugged though.

My set has similar problems as yours, will power on w/button/remote can hear beeps when volume pressed up/down but no display or faint glow on panel.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Magic Smoke, thanks for all the info, i'll try this on sunday evening. what connector do you use to jumper PS-ON, and VS-ON. I tried the test by disconnecting LVDS cable , and jumpering the two top pins on Main logic board, with no results. My main logic board has no visible led lights flashing at all when powered up, dead. Thanks again, George I also found a bad diode on PSU, DB803 I think, I'm not looking at my set right now. It's giving voltage in Diode mode in both directions.

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

To confirm if DB803 is bad, can you supply a photo of it, or the part #?
Try unplugging X and Y-main boards with your jumpers in place, do you get Vs & Va?

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

I cannot see the legend on the other side of CN801 and CN802 in your pic of PSU, the wires are covering.

My PSU only has 2 connectors for power, yours has 3.

On mine PS-on and VS-on are on the same connector, in my case CN804. Pin 1&2 for PS-on and GND with pin 4&6 for VS-on and 5.3v.

Yours might be different. The legends will indicate which pins to use.

Disconnect all 3 power wires from other boards for this test. This will tell you if PSU is generating the proper VA and VS voltages. Then you can proceed in testing other parts.

DB803 on my PSU reads voltage in both directions with meter in diode mode also and it is generating correct voltages when jumpered on.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Gentlemen I didn't get a chance to do anything with my set today. I will get on it Mon morning. Tom, I will get pic of diode, and try to read part # I will also load up closer photos of psu. What connector do I do all this jumpering On. Should I remove the diode and check it out of circuit, to be sure if its bad or not. I always thought diodes as having voltage flow in one direction, and if it flows both ways its bad.

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

The connector you are jumpering links the power board and the main A/V board; the main A/V board has the video inputs on it.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Thanks tom, i'll get those pics loaded, I can't see the writing on diode so I'll take it out, and check after I do this test, will post results soon.Do I have to disconnect the ribbon cables from the bottom of y,x main also to do this test or just disconnect the power to y main. My x, and y are connected together. Just want to make sure before I do this, don't want to do any more damage, Thanks All.