Samsung plasma PN50C550G1F/ Sound, no picture

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Tom, Magic smoke, I jumpered PS-ON to gnd, and VS-ON to 5.3V, and disconnected Both x,y main +LVDS cable, Both VS and VA voltages came up to normal steady voltage. VS now reads 212.5V, and VA 48.9V Panel label says VS should be 211V, and VA should be 55V. Both voltages are steady. No test patterns were visible, nothing, even checked in a dark room. I would assume that PSU is OK, and Main logic board is bad. New pics are in album on Imgur, there are 15 in total. Tom I did try to get a close pic of that Diode, best I can get for now. Other pics are of all the cables that I disconnected. Where do I go from here, any other tests, thanks a million for your Patience, I enjoy learning about these tv's. Excuse the crude method of jumpering, I used a thin piece of copper wire, worked like a charm. http://rccrasher65.imgur.com

[mmartell]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

You cannot disconnect XMain and YMain and expect a picture. Plug them back in.

[mmartell]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Err nevermind that I see now you were checking the psu for vs and va.

[rccrasher65]

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.

Tom I got both VA and VS voltages to come up to normal, safe to assume bad main logic board, no test pattern at all. PSU is good then, correct.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Gentlemen, are there any other tests I can do now, or should I just replace bad Main logic board first, and go from there. Can I connect the x,y main boards back, to check if I get proper voltages when they are connected, or will that damage something. (while the connector is still jumpered) that is, because I get proper voltage with them jumpered. Thanks again, George

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Tom, should I check that diode out of circuit to make sure its bad?

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

If PSU is making the correct voltage the diode should be fine. The diode on my PSU at DB803 reads as bad in circuit and it makes the correct voltages. If it's bugging you desolder one end and retest.

You can adjust the trim pots to get the VA & VS adjusted to sticker spec. Your VA is a little low.

Do not reconnect anything with PSU powered up, unplug and wait at least 2 min before connecting. It takes a bit for the residual VS & VA voltage to bleed off with no load on it.

I believe it is safe to say that no led blinking on logic board means it is not functioning (when it is all connected).

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Can I plug in x and y main to see if voltages are correct, while I have every thing jumpered, or will it do more damage.

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

You can leave the jumpers in but unplug the power cord and wait a few min for residual power to dissipate before making any other connections.

You should at least disconnect the buffer boards from X&Y to prevent panel damage if they overvoltage from no logic control connected.

I did this test to my set trying to see if X & Y were making the correct volts, but I think logic board controls the circuitry for Vscan and VE voltages. I did not get any Vscan or VE volts when I tried it.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Magic Smoke, thanks, I think I'll just get the replacement first, then go from there.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Magic Smoke, thanks, I think I'll just get the replacement first, then go from there.

i removed the main logic board today and started looking at it closer, and decided to check the fuse, since board was completely dead, no led's lit at all, and i didn't get a reading at all on fuse. do you have to have power supplied to board to get a reading to check surface mounted fuse. It's labeled F2000 on my board.

[vinceroger69]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

are you testing it in ohm mode on your multi meter? if you are then the fuse could be open circuit

[MagicSmoke]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

If your meter has a tone mode and you get no tone then fuse is bad, if just OHM settings it should read 0 if good, 1 or no meter change means it's blown.

^ This is w/no power on it, if it was powered on it should have 3-5 volts on both sides.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

are you testing it in ohm mode on your multi meter? if you are then the fuse could be open circuit

yes I am. My meter is a Klein MM200 auto ranging digital Multimeter.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

If your meter has a tone mode and you get no tone then fuse is bad, if just OHM settings it should read 0 if good, 1 or no meter change means it's blown.

^ This is w/no power on it, if it was powered on it should have 3-5 volts on both sides.

ok , thanks I'll check again. I have several meters. some plain digital, others more advanced, with function keys for each setting. I also pulled the PSU, to check that Diode. My eyes are not what they used to be, but the number on it is 4007, 0A06 from what i can make out . Tom I know you asked me for some Part number, does this make sense to you. From what I picked up on research and here, a diode acts like a one way gate, giving voltage in one direction, this one gives voltage in both directions, even though all voltages are correct on PSU, after jumpering PS-ON, and VS-ON. Magic smoke, I made a mistake on the reading of VA, a few post back. VA voltage should read 55V my reading was 54.8V not 48V as posted earlier, so no need to adjust the pots. Maybe the 212.5V down a little to panel label of 211V.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

up date, fuse is blown, it has a 5a on it, where can i get them. Will Digikey, or mouser sell one or do I need to buy more.

[tom66]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Can you show us a picture of it?

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Tom, Thanks I'll show pic of fuse, and Diode. fuse is Little brand 5A SMF 125V.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Sorry, Gentlemen I had a wedding too attend so I'll get those pics up on Monday , new logic board should be here soon, thanks for your patience.

[rccrasher65]

Re: Samsung plasma PN50C550G1F/ Sound, no picture

Gents, sorry for the delay with the pics, they are at http://rccrasher65.imgur.com Tom would this blown fuse cause the logic board to fail like it did? I ordered some off of ebay to try.$3.00. would this blown fuse protect the rest of the board or is it shot. I got a replacement coming anyway just in case I need it. I wanted to try a component level repair, instead of being a board swapper. thanks again for all the help guy's.