Samsung 46" LED Ua46C6900 : power on prob

[Geniee33]

I have a Ua46C6900 which has a strange problem.
If i try to turn it on, it will attempt, click, click, flashing red standby light, then click off without showing anything on the screen.
I have checked the PSU caps and they appear ok, i pulled them all out and did ESR tests and most were ok, however i did buy a new PSU board from online (new one still has SamWha caps tho) and it worked once, then same problem.
If i unplug the TV for 10mins-1hour then plug in, and turn on, it will work. but if i turn off, it will require me to unplug again, leave it off, before plugging back in and turning on.
I have tried isolating the board by removing Tcon, speakers, re-seated tcon cable, clenaed it all, still same prob.

All fuses are ok.

I have done factory reset using service menu, same prob.

Im a little lost at the moment, i have a whole bunch of rubycon caps coming from ebay so i can replace all caps on the first board, but i dont know where to go now?

Can anyone help?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

You need to check the standby Voltage to see if it is steady, need to check the PS-ON signal to see if it is present and steady when the TV is not working.
You also need to upload good clear pictures of the whole back side of the TV so we can see all the boards.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, yea i checked the standby a long time ago and it was steady, i also should mention i have checked all fuses and they are also fine.
I will get some detailed pics tonight and upload them.
I did see another Samsung video on YT where the guy unplugged what seemed like a small data cable off his main board which went to some form of Wifi/RF receiver and the his turned on with no problems, i had a look on mine and didnt have this cable/module.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

Ive added some pics.
While i was trying to get some voltage readings tonight, it turned on and i couldnt reproduce the problem.
But tomorrow if i leave it plugged in, i will be able to get some readings.
While it was on, i was getting correct readings on the vamps, 12v standby etc.
But the fact its on, that's expected.

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

What you need to find is what is missing on the connector between the main board and the power supply baord when it is not working.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

Yep, hopefully when i go home tonight it will not want to play ball and i can get some readings.
I will measure all of the 18x pins when in standby, then what pin should i be watching when pressing the power on?

-vamps
-vamps
-PS
-SB (im guessing standby?)
-H-Sy
-PWM
-BL
-DET

Could you please help me understand what each of the abbreviations on the board means?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

What is the power supply board P/N BN??-?????
Is it BN44-00357B or 00367b?
Pictures are too blurry for my eyes.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

Its a BN44-00357B

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

https://www.badcaps.net/forum/showpo...3&postcount=22
As you can see, there is a chart for the pins of the connector, the pictures did not show ALL the pin numbers and the pin names, we need them ,and the pictures of the charts on the power supply board.
You may want to read the thread also.
https://www.badcaps.net/forum/showth...ht=BN44-00357B

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, ill get a closeup tonight. (that looks like the same key on my board.)
I will try some of the work in that thread and come back with some info.
thanks for the links,.

oh wow, that link you gave me looks almost exactly the same from the back,

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, i got some readings tonight on those 18 pins.
I also took a picture of the key on my second board (they are the same).

It was a little tricky, because as it was cycling, i was seeing voltages jump and drop, and then it started working... Grrrr

Half way through my testing as it came on, it kind of ruined my test results...
I will try get a full reading when its on Vs off (standby light) Vs cycling.

Here are mostly the results from it being on

Anyways, here are the details while it was cycling.

Vamp - 17v -> 0 (cycling) solid 17v when on
Vamp - 17v -> 0 (cycling) solid 17v when on
5.3 - 5.3 -> 0 (cycling) solid 5.3 when on
5.3 - 5.3 -> 0 (cycling) solid 5.3 when on
Gnd - yes its fine
Gnd - fine
12v - 12.5
12v - 12.5
12v - 12.v
PS - 3.1
SB - 0
5.3 - 5.2
H-Sy - i missed this one
PWM - 3.3
BL - 4.8
DET - 5.2

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

So 'SB' is just sitting at '0' and not cycling up and down?

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

i believe when it was turned on, it was then @ 0.
I will check tonight what SB has when the set is off, but red LED on front.
Does that make sense that the Standby would drop to 0 when the tv is on ?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

OK, SB is the STANDBY 5.3V for running the main board, this SB is fed into MOSFET switch for producing the D5.3V which is turned on when PS-ON is present on pin 18.
You also indicated that the D12V is solid but the VAMP is cycling, these two Voltages are generated by the same circuit and from the same power transformer so to have one solid one going up and down is not possible.
You also indicated that the SB (STANDBY 5.3V) on pin 16 is 0 Volt, that is impossible because the main board needs this SB Voltage to run so it can send out the PS-ON (you indicated 3.1V) to pin 18 of the power supply board.
So there must be error in your measurement some where because it is impossible to have standby SB of 0 Volt! and yet the D5.3V is cycling.
Bottom line, no SB then there will be no other Voltages.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, i just checked with the plug disconnected from the mainboard (for easier multimeter access) and the TV plugged in, but not switched on. (red LED on front).
The only 2 pins i got 5.3 voltatages off were
SB and PWM

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

I then went and tried turning it on. and you are right, my multimeter was a little slow, the PS is only at 3.1v while its trying to come on then drops to 0 when it clicks off.
all the 17v and 5.3 drop to 0 before back up to 17 / 5.3

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

PS (PS-ON) >2.5V = ON = OK, <1V= OFF.
So what we are interested in the SB (STANDBY 5.3V) it should be there and steady the minute you plug the TV into the outlet and with all the board connected, if it is not then you need to check the SB section first.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, i just went and checked the standby volts, and its solid at 5.3 when tv is off, and when i turn it on, it stays at 5.3
PS is on 0 when TV off, then when turning on, it goes to 3.1, clicks, PS drops to 0, tries turning on again, backup to 3.1 and in this test, the tv stayed on, and the PS stayed stable at 3.1
Its hard to get consistent info, because it will turn on randomly when trying, other times, i can be at it for 5 mins, unplugging from wall, letting it sit, plugging back in and it will turn off.

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

The main key is that we need to have STEADY SB Voltage feeding the main board, if we but the PS Control signal does not stay >2.5VDC or going up and down but the SB is steady, that will indicate the problem in the main board.
So is SB stay at solid 5.3? If it is, then we need find out why the PS does not stay HIGH when power switch is activated.
We can also force on the PS line for testing.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

is that with unplugging the cable from the power supply board to the mainboard and jumpering the pins SB and PS ?