42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

[vinceroger69]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

ive had a quick look for a replacement board but cant seem to find one to match so not sure what too suggest now i dont know if these sets suffer from bad bga soldering on the chip thats under the black heatsink, i wonder if its worth removing the heat sink and reflowing that ic with some heat? the only other option i guess is to phone around and see if theres a repair service available? A question though have you saw this tv working? is the panel fine no lines etc as if so it may not be worth spending too much cash on this tv.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

It's all explained in post # 1.
how do I get that finned heat sink off the chip? Just heat everything and try to get it to flow?

[vinceroger69]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

see what other peoples thoughts on it possibly being a bga issue first as you could do damage trying to remove the heatsink (glued on i think but usually come of quite easily) i have a hot air station but in the past have used a heat gun on them but its quite risky as too much heat can damage them too. basically you just want to melt/reflow the solder balls under the ic (but this sometimes only last a short while) but that may not be the issue it could be a lot of diffrent things

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Thanks for the reply VR. I'll see what I can find out.

[martino]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Did you measure the voltage regulators on the mainboard? Did you try to freeze sections of the mainboard to see if it has effect?(can of air up side down,short prays on target area).
Did you try and heat up sections of the mainboard to see if it has effect?(hair dryer,paint stripper)

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Hi Martino, Thanks for the reply. As I stated in post # 1 this is an intermittent problem that only occurs on start-up. I don't know if this can be caused by bad connection? bad cap?bad chip? out of spec component? I think I need someone with experience in testing samsung main boards to chip in and help. If your that person fire away. I know how to use a VOM. and a soldering iron but not so much about electronics except for what I learned as a Mercedes Tech 20 years ago.

[martino]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

often problems that occur on start up are components that are on the edge of failure.
When they are cold they have a different value then when warm.Might be just enough to work or not work.
The freeze them,heat them can very nicely give away their secret so to speak.
A voltage regulator that let's say has a output voltage of 1.8 volts,but when cold only gets to 1.65 volt can already be enough for a failed start.But when trying to turn on the tv a few times the temp inside that regulator has risen enough that it now gives 1.8 volt again and oh my,the tv works again.
What i'm trying to say is that with freezing and or heating,you can sometimes find the area on a board where the bad guy is,and therefore close in on it.
I have had boards that I froze first in the reactive areas and with solder iron touched each component one by one to find the bad guy. It sometimes helps,not always.In this case where it's hard to find a replacement this might be something to try,dunno.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Ok, thanks, I'll try that.Finally found samsung parts and while they couldn't find my exact board a similar replacement is $539.00 lol, that's what I paid for the tv 8 years ago.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Back to square 1 now only stand by light, won't turn on blue light...sigh..

[vinceroger69]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

ok as it now wont turn on try heating each board see if heat makes it turn on start with power supply then the main board i use a hair dryer for roughly three minutes not to close or to hot as capacitors can explode with too much heat

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

ok as it now wont turn on try heating each board see if heat makes it turn on start with power supply then the main board i use a hair dryer for roughly three minutes not to close or to hot as capacitors can explode with too much heat

Thanks for the reply.I tried heating the big ic with the heat sink on top and no joy and I got it pretty hot but no change never tried any others but will give it a shot and also the power supply. MAYBE A LOAD BANG MAY BE A BLESSING.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Ah, the saga continues...... I finally got a main board from a gentleman who said it was fully tested and so it appears to me as the heat sink on the large chip in the center is askew and several caps have been marked with a black dot, so I installed this board plugged the tv in and VOILA,, I'm still at the same problem.
I have replaced the PSU, the logic board and the Main board, still have no picture,can get the test pattern screen when pins 3 and 4 are jumped on the logic board. What I find stange is that when plugged in the stand-by light comes on and then a couple of clicks and I can turn on the blue light with it's accompaning couple clicks and the screen will flash a bit, I think it gets slightly lighter, but no picture and the remote no longer will do anything. I sincerely hope someone has some help for this problem. Thanks.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Bump

[ReeceyBurger123]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

The boards your getting must be faulty, or you have something like a broken wire.

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

thanks for the reply Reecey, DO YOU THINK IT'S THE main board thats the problem and is there a way to test it before I return it. (sorry about the caps)
PS the boards all from different suppliers..

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

I'm going to try to test the voltage regulators (7) on the main board . I found a great video on the site, as it seems to me like a reg slightly out of wack could be the cause.
I'll try to get it done tomorow.

[vinceroger69]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

sorry to hear the replacement mainboard hasnt fixed the issue was the new board a exact match all numbers etc? also what boards have you swapped now in this set?
could the board you run the test patterns on be at fault? hopefully a more experienced member will know.
also as this set did work at times do it still work sometimes now or not at all?

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Hi VR , main board was a exact mach an d had previously replaced power board and logic board.Will not get pic any more.
So I've tested the v/regs voltages and I think 2 are suspect but I need a more experienced opinion so please speak up (TOM66) :-)
The no's are AIC
1084PM
397H1 Vout 3.3 Vin 5v
There are 3 of these, my readings are as follow useing the left pin as pin 1.

First reg. 1=0.57 2=1.81 3=3.29
Second reg 1=2.04 2=3.29 3.29
Third reg 1=1.26 2=0 3=5.14
Help?

[vinceroger69]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

can you put your old mainboard back in and take the readings on the same 3 voltage regs whilst your waiting for a answer budm may have a idea if these voltages are in spec or bad

[rich-t]

Re: 42"Fluid plasma tv Mod#(Samsung)pn50b550t2f

Yeah, but I have to go shopping first, my dog is hungry. :-)