Samsung 46" LED Ua46C6900 : power on prob

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

So, i have been watching heaps of videos, and is this correct..

the Standby is constant 5.3 v, when u press the power button, it sends a signal over the PWM 3.3 to tell the mainboard to trigger power on the PS which then kicks the power supply to turn on its backlight and other functions?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

The Standby power supply is an always on power supply to run the main board, they run 24/7 the minute you plug the TV into the outlet. When you hit the power switch or PWR button on the remote, the main board then sends out the PS-ON signal (not PWM, it is >2.5VDC for ON, <1V = OFF) to turn on the switched power supply sections, after a slight delay, the board then sends out the BL-ON signal to turn on the backlights circuit, the main board also sends out the DIMMING signal (it can be analog level between 0~5VDC (5VDC = MAX LAMP LEVEL), or PWM (Pulse Width Modulation, about 200~300 Hz, 10% pulse width = min lamp level, 90% = Max lamps level).
The main board also send the ON signal to turn the electronics switch to supply the B+ to the T-CON board. For all these to function, you must start with solid STANDBY Voltage. Read my basic LCD TV/Monitor Troubleshooting guide.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

hmm, i had a look through your guide... im not sure what i should be doing im sorry.
the return signal from the mainboard PSon is at 3v when its trying to powerup, and then just clicks, and drops off again.. should i remove the mainboard plug and jumper the standby and PS0n pins to try to turn it on without the mainboard in the loop ?
I have tried isolating the problem by trying to turn on with each plug disconnected but nothing seems consistent. it looks like all the power supply pins are doing what they are supposed to when its attempting to poweron.

With it turned on, I checked the BL and that was showing 4.9 and the DET too showing 5.3 and the PWM will move from .3v (backlight setting on 0) to 5.3 (backlight setting to 20 (max)

Im wondering if i leave the backlight setting either higher or lower than it was on, and see if that makes a difference to the reliability of it turning on or off?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

"the standby and PS0n pins to try to turn it on without the mainboard in the loop ? " Yes but us the 470~1K resistor instead of direct connection in case you have accident so the current will be limit, but you MUST disconnect that PS-PON wire going back to the main board first. Try that and see if the TV will stay on with backlights and images on the screen.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok, so i will disconnect the 18 pin cable form the mainboard,
put a resister between pins 16 and 18
try turn it on, see if it stays on without clicking and get backlights turn on etc.

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

You will have that connector put back in place without pin 18 wire in place (the wire on pin 18 that you removed will then be connected to pin 16 through the resistor, so the main board will get the SB Voltage to run and also for the main board to be able to send the bl-on an di signals to turn on the backlight.
If you do not have the connector plug in, then all you are doing is to force the power supply on only and the main board will be dead due to no power, if you want the backlights to be on also, then you will need another resistor to force on the BL PIN.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

Hmmm, but in the other thread, the guy did the jumper between pins 16 and 18

https://www.badcaps.net/forum/showpo...7&postcount=26

Going off their theorys, if i do that, i could turn the tv on, and the power supply should click but would it stay on, ? or would it do what its doing now, cycle on and off clicking its head off?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

"Hmmm, but in the other thread, the guy did the jumper between pins 16 and 18" That is to turn the power supply on, he did not show how to turn on the backlights did he? Unless the BL-ON line is already has the pull-up resistor to make BL-ON pin HIGH. Try it as shown in that link and see if you will get the backlights.
When you force the power supply on by using the resistor, then the power supply should stay on as long as the resistor is in place to simulate the PS-ON signal.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

yep, i guess that will give us more information.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

ok when i got home tonight, i put a peice of wire between 16 and 18, stood back, plugged the power cable in. power supply clicked on, stayed on, backlights were on and it was showing blue on the screen. So is this telling us its somthing on the mainboard that might be the problem ?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

It is telling you that the main board is not sending the proper PS-on to turn on the power supply, and the BL-ON line has built-in pull-up resistor so it does not need the resistor for forcing on the backlights.
So you need main board.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

It is telling you that the main board is not sending the proper PS-on to turn on the power supply, and the BL-ON line has built-in pull-up resistor so it does not need the resistor for forcing on the backlights.
So you need main board.

damn, Is there anything i can check on the main board?
any common faults ?

[budm]

Re: Samsung 46" LED Ua46C6900 : power on prob

You can try pushing on the board to see if it may have bad connections, also try cooling and heating to see what it does.

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

hmm, yea...
Ive been reading over at the sammygo forums, and would an EEPROM reset help here?
Even tho, i have done a full service menu reset in the past with no real change.

Also, those guys over there are talking a lot about replacing mainboards from same generation TV's with success. eg. Replace a C6000 with a C6500 mainboard.

Im having trouble finding my particular mainboard on shopjimmy or the web.
Im wondering if the UA / UE is important or not, and that only the Cxxxxx needs to be similar (or newer than the model you are upgrading) ?

[Geniee33]

Re: Samsung 46" LED Ua46C6900 : power on prob

Bit of an update.
I took the mainboard off last night, took off the 3x stone heatsinks from the processors, pre-heated the oven for 10mins at 200degC
Then put board in the oven for 10 mins at 200degC.
I then turned oven off, opened the door and let it cool for 30mins.
Once i put it back in the TV, it powered on immediately when pressing power.
This wasnt too suprizing, as i had found unplugging it for an hour or so would generally work the first time after replugging it in.
Whats new is that, i was able to turn it off and on throughout the rest of the night without any issues.
I left it plugged in overnight (standby) and first thing this morning, it powered right up like its supposed to.
So, i wont get too excited untill its behaving itself for a few more days, but its looking promising that this may have fixed it.

FYI, i was talking over at the samygo forums and they say the following regarding using different mainboards.

--
The C6800 board should be ok for you, its also ok to take boards from different panel sizes. Just check that the baord has the right tuner (DVB-C / S2 /Dual...)
the 6800 / 6900 can be set in advanced service menu, i dont exactly know the difference.
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