Samsung UA60EH600 weird startup

[The_Todd]

Hello guys,


So this issue has really got my head scratching...

So this came in no picture and blinking red led. (Wow much original)

Anyway all caps are fine, 5v standby is fine, and from what I can mesure the power transistors are also working fine, but nothing..... Anyway...

I was doing some voltage checks on the power cable that goes to the main board (disconected from mainboard) and upon testing the power on/on cable is just turns on as far as back light and voltages are concerned..... And stays on???

Plug it back in to mainbaord and it working semi ok, apart from staggered startup.

So my logic is this.
A normal board is normally off unless otherwise said
This appears to be on unless otherwise said....wtf

So Q1. What the hell did i do?
Q2. How does the power pins work? Is it to ground or to 5v? And with a resistor
Q3. Whats the difference between "power on/off" and " BLU_on/off"

Q4 on a slighly diffrent topic there is a smd resistor looking thing with a marking "30C" and is labled RQ864 what is it?

Cheers, thanks.

[The_Todd]

Re: Samsung UA60EH600 weird startup

And here is the pin layout for the cable.

Oh also my guess for this problem is a dodgy transistor, before it was stuck close and now it is stuck open?

I also forgot to mention that i was "TOLD" this tv would turn off and on randomly, (caps i thought) but no, not that easy

[The_Todd]

Re: Samsung UA60EH600 weird startup

Hey sorry to ask 9001 questions,
But regaurding the back light curcuit, as the is essentially 4 outputs ( what goes into 6 wires) all controlled by 4 mosfets. Is it controling 2 lots of leds curcuits with a positive and a negative gate? Or am i way off and need to check myself?

Cheers

[budm]

Re: Samsung UA60EH600 weird startup

So let me get this straight, if you disconnect the cable between the power supply/LED driver board BN44-00500A and the main board then apply AC you will the get the backlights to come on right away and backlights stay on as long as the TV is plugged into the AC outlet?
If that is the case then your power supply board is OK, this power supply probably has pull-up resistors for doing the self test.
We also need good clear pictures of the whole back side of the TV so we can see how all the boards are connected together.

"power on/off" = PS-ON/OFF
" BLU_on/off" = BL-ON/OFF = Backlights ON/OFF
You have two set of LED strings so it has two MOSFETs for two Boost converter circuits, two PWM Controlled MOSFET for controlling the current through each string of the LED.

[The_Todd]

Re: Samsung UA60EH600 weird startup

Yes, with power connected, but mainboard left unconected it "turns on"
Also in this setup the only thing connected is the backlight. This is very weird everyother board i have worked on is always off unless activated.

What is the purpose of this pullup resistor to turn it on? Does this mean the main board keeps it "off" in other words the powerboard is always on, unless it has been told to stay off?


Picture included

[budm]

Re: Samsung UA60EH600 weird startup

Yes, with power connected, but mainboard left unconected it "turns on"
Also in this setup the only thing connected is the backlight. This is very weird everyother board i have worked on is always off unless activated.

What is the purpose of this pullup resistor to turn it on? Does this mean the main board keeps it "off" in other words the powerboard is always on, unless it has been told to stay off?


Picture included

The pull-up resistors are for simulating the ON command signal from the main board so the tech can easily isolate the problem in the field instead of using resistor between STBY power supply and the PS-ON pin and the BL-ON pin while trying to service the TV. They did not do that in the earlier version of the TVs so you have to do the force on yourself with the resistors.
Sounds like you have problem in the main board. You can record the DC V on the PWR ON/OFF pin and the BLU-ON/OFF pins as they are right now without the main board connected and the compare them to the readings when all boards are connected and the TV is not working so you can see what are missing.

[The_Todd]

Re: Samsung UA60EH600 weird startup

Oh wow, I didnt know that, thanks for the advice,

Well as I said originally this was not working, even when disconected, then after slightly grounding pwr on, its now working normmally, doesnt make sense to me...

So is are the to power pins meant to be shorted to ground to turn on or conect to 5v to turn on?

Cheers.

[The_Todd]

Re: Samsung UA60EH600 weird startup

Ok so these are the test results

No main board
Pwr - around 3v but keeps jumping around anthing down to 1.5v also makes the psu make a soft buzz noise everytime conected to the multimeter...weird
BLU - 3v exactly

With main board conected (and tv on)
Pwr - same as above
Blu - 5.9v

Main board (standby mode)
Pwr 0.4 jumping occasionally to 0
Blu - 0v

Why is pwr acting so strange....


Cheers

[The_Todd]

Re: Samsung UA60EH600 weird startup

Well, I did resolder a couple of startup capacitors on the primamry side of the main transformer curcuit, and its been running 2 hours non stop. Still i have my doubts..... Guess it was a dry join, Time will tell.

The overal power pins cucuit still leaves me a bit confused. Ive also realised this actually has dynamic backlighting, is this what the BLU curcuit is for? Variance to pin voltage variances the out put voltage to the leds?

[vinceroger69]

Re: Samsung UA60EH600 weird startup

when re soldering the capacitors on the power supply the heat may of lowered the esr on them hence the set is now starting up ok if it fails too start again just replace the capacitors with Panasonic brand

[budm]

Re: Samsung UA60EH600 weird startup

I would also re-solder all the transformer legs and all the legs of the components that are mounted to the heatsink, especially the one with through rivets.