Samsung LN40A500T1F

[dietzcj]

Re: Samsung LN40A500T1F

I got the main board replacement today from amazon, but it still didn't work.
Not sure what I should do now, except ebay the boards and get my cash back out of it.

[mmartell]

Re: Samsung LN40A500T1F

Did you test for switched 5v from the psu when you jumped it ? Bad caps or other problem in the output section ??

Maybe test all voltages when you jumper the ps especially those going to the main board.

[dietzcj]

Re: Samsung LN40A500T1F

I thought that when the backlights came on that the PSU was okay. Also I did not have the main board plugged in when I "Jumped" it with the 1k resistors.
Should I try that with it plugged in ?

[johnboy1313]

Re: Samsung LN40A500T1F

Unplug the tcon, leave the main plugged into the power supply, and and see if the set will power up.

[dietzcj]

Re: Samsung LN40A500T1F

Yes, I tried just unplugging the Tcon board and it just blinks red light by the power switch.

[mmartell]

Re: Samsung LN40A500T1F

Hmm.. you have a good standby voltage which should provide you with a solid light (no errors) if the main was good. Try unplugging speakers and aux input board even button assembly from the main board and see if light stops flashing.

[dietzcj]

Re: Samsung LN40A500T1F

okay, mmartell.
Tried that also. Unplugged the speakers and then the power switch.
Should I still have the 1k resistors still jumped in at this point? Right now I have them removed from the previous experiment.

[mmartell]

Re: Samsung LN40A500T1F

No jumpers. Just trying to figure out if some peripheral is pulling down the mainboard and hampering it from operating normally.

There was a thread around here where a guy found a fault on the powerswitch/ir daughterboard that prevented the set from working at all. Anything is possible.

[dietzcj]

Re: Samsung LN40A500T1F

So maybe try to bypass the on switch using the same technique ?
Btw, the main board is a BN94-02257A. and I have posted previous pics.
The connector from the power switch is (Pin 1-IR)(Pin 2-gnd) (Pin 3-stb3.3) (Pin 6 Key1) (Pin 7-Key2) (Pin 8-stb5v). So maybe try Pjn2 and Pin 8 with the 1k resistor ?

[mmartell]

Re: Samsung LN40A500T1F

No I'm not suggesting that. But I see now the ir receiver is on the same plug as the power switch so it's kind of deaf and dumb without it.

An easy thing to try first is to unplug that connector and listen for any relay clicks and such when you plug it in. Does it sound any different ?

You would have to make sure which pins to jump to simulate the power button before moving forward with that idea.

[dietzcj]

Re: Samsung LN40A500T1F

no relay clicks. But without the power button how is it turning on ?

[mmartell]

Re: Samsung LN40A500T1F

It's not turning on but if it sounded different in any way when plugged to mains could indicate the power switch/ir board causing the set difficulties.

Trace the powerswitch wires to jump it manually - after that it would seem you have inserted another bad main board.

[dietzcj]

Re: Samsung LN40A500T1F

try jumping the 2 solder points for the power button ? With a resistor or straight alligator clips ?

[dietzcj]

Re: Samsung LN40A500T1F

the 2 points in red ?

[dietzcj]

Re: Samsung LN40A500T1F

okay, I just tried it and it did not work.
I think I will try testing each bulb individually. If it is shutting down a broken bulb could be the issue, or the inverter card.

[dietzcj]

Re: Samsung LN40A500T1F

I saw a you-tube video where someone was jumping 2 points together because the ccfl bulb was bad.
http://www.youtube.com/watch?v=oE6K4xBVweA
What if I made a harness to plug in instead of the CCFL closing the circuit. That would bypass the light itself to just test each light individually.

[dietzcj]

Re: Samsung LN40A500T1F

Okay final post, I got my replacement power supply board and it is now working.
Thanks to all who helped me, I really appreciate it very much. BADCAPS Rules !!!!

[ned1]

Re: Samsung LN40A500T1F

Okay final post, I got my replacement power supply board and it is now working.
Thanks to all who helped me, I really appreciate it very much. BADCAPS Rules !!!!

I know this is all post but wanted to share some information about what I did to fix problem on same TV model. Mine had high pitch noise and sometimes will not turn on, also vertical lines. I traced it to the bad main board. Since I could not find replacement for reasonable price I fixed old board. I washed the back of the board with DI water, scrubbed with old toothbrush. Dried it in the convection oven for 2 hours at 80 C. Also used solder iron to touch up few solder connections that looked bad and got tv working.