Samsung plasma wont power on pn50a550

[dick_barton]

Re: Samsung plasma wont power on pn50a550

Do i disconnect power cable to main or just the lvds?

And where are pins 3-4 on logic?

Disconnect the ribbon going to the main board and short the pins mentioned then power up.
If you have the test patterns displayed then it generally indicates a mainboard problem.

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Well i replaced c102 with an alum low esr cap and it did not fix issue

Tv still cycles on and off indefinitely

The general repair kit for this model tv main board is actualyy 2 ics and 1 cap ...i wonder if i need the ics also

Which pins do i short on which board.....i included a pic of logic board few posts earler

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Are pins 1/3 on the bottom right of logic ...top 2 pins?....in the group of 4 pins?

See photo i posted earlier

[shelby5041]

Re: Samsung plasma wont power on pn50a550

I mean pins 3/4.....

I dont see a pin marked 4 but i do see 123....i can assume the other pin is 4?

[shelby5041]

Re: Samsung plasma wont power on pn50a550

And which cable do i disconnect?

The lvds or power ribbon cables going to main?

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Ok i removed the lvds cable from logic to main and jumpered pins 3/4 on logic and tv still cycles on and off and repeats indefinitely

Tv screen does not actually power on at all....no samsung jingle...nothing

But i do get good voltages coming from ps

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Correction....i do get some type of test pattern....i forgot to hook up buffer cables back..

I get red blue green solid display when i did what u said so that probably isolates to main board issue as you guys stated?

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Update....for the heck of it i let tv cycle on and off for over 1 hr and tv finally got the samsung jingle and tv turned on with good picture

Im hoping to get this issue fixed...at least i know display panel is good lol.....

[attainteddragon]

Re: Samsung plasma wont power on pn50a550

if you got your test patterns with the control board jumped, then you should be on the right track looking at the main.

just remember that tantalum caps have the anode marked and electrolytics have the cathode marked. easy to put it in backwards.

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Yes i put in the electrlytic opposite...i get good 3.3 volts......cap wasnt the issue

Still searching for issue hope someone can help

[shelby5041]

Re: Samsung plasma wont power on pn50a550

The surface mount cap had band positive so i installed the electro cap with band opposite of band where old cap was.....it was done correct

[shelby5041]

Re: Samsung plasma wont power on pn50a550

My opinion is its a grahpics or memory chip issue....seems very similar to a hp laptop issue very common that laptop only powers on aftercseveral tries and stays on sometimes when on....after reflowing gpu chip it temporarily fixes issue

should i try reflowing again?...or will this stress board too much

[kc8adu]

Re: Samsung plasma wont power on pn50a550

there are 2 47uf tantalum/poly caps in 2 seperate dc-dc bucks in that area.
replace both.
never had to replace ic.its always those 2 caps.
3.3 usually dies first.
iirc the other is 2.5.
i have some 100/16 polys i use.
a bit big but still fit with a bit of care.

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Thanks i donget 3.3 volts at cpu

So my c102 is good

Dno u know the other cap location?.....since im getting good 3.3 v not surecwhat changing it would do

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Sorry didnt see the 2.5v.....do u know location...or test points for the 2.5v?

[shelby5041]

Re: Samsung plasma wont power on pn50a550

I mean i do get 3.3 v......i hate touchscreens lol

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Hi here is a photo of bottom of board...can u tell me where the 2.5v output cap is....i already replaced c102 the 3.3v output cap....didnt fix issue

[shelby5041]

Re: Samsung plasma wont power on pn50a550

I found c131 it was on top side of board not bottom like c102 is on

They are both same spec caps....i will try to replace c131

To test voltage on c131 would i just meter both ends of cap and should be 2.5v?

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Top of board photo

[shelby5041]

Re: Samsung plasma wont power on pn50a550

Hi kc8adu

I replaced both caps c102 c131 tv still cycling on and off

Any ideas?