UE55F7000ST clicking on/off

[shandy]

Samsung led tv UE55F7000ST
having problems diagnosing this TV

The common problem that i'm having is the relay in the power supply board clicks on and off, at same time backlight goes on and off and can briefly see the smart tv logo.

At the moment I'm thinking it is a faulty tcon board and if i disconnect it the tv will power on and stay on with sound coming through as it would normally but no smart tv logo.

The strange thing I found is if I leave it turned off for a long period
of time say overnight the TV will come on as normal, then I
start thinking maybe the tcon board is ok after all but then when
I turn it off and on again I get the clicking on and off again.

the PS board will click a bit faster with the main board disconnected
and with the two backlight cables connected or disconnected so would
that indicate something wrong with the PS Board, all capacitors look
normal with no bulges.

Any help of insight greatly appreciated.

Shandy

[nomoresonys]

Re: UE55F7000ST clicking on/off

Check solder joints.

[shandy]

Re: UE55F7000ST clicking on/off

Many thanks for your reply, I did actually look at the solder joints under magnification
and touched some up, I should have mentioned that.

[Diah]

Re: UE55F7000ST clicking on/off

you have sort of test wasnt complete at explaination.
the most things now.. disconnect the main boards from PCB, and plug it in the wall see the back light come on and stay on... or not...

[shandy]

Re: UE55F7000ST clicking on/off

Many thanks for your reply!

With the main board disconnected the power supply board clicks a bit faster
and the backlights go on and off at the same time.

[nomoresonys]

Re: UE55F7000ST clicking on/off

ok, unplug everything from powerboard backlights and all, then plug power cord in, see if clicking or anything changes.

[shandy]

Re: UE55F7000ST clicking on/off

Many thanks for your reply

I think you maybe helping me get there!

I unplugged all leads from power supply first time power on no clicking
turned off and on again it clicks a bit faster still

[nomoresonys]

Re: UE55F7000ST clicking on/off

so the first time nothing no click at all? second time steady clicking? did you try it again?

[shandy]

Re: UE55F7000ST clicking on/off

yes that's correct it clicks every time, my guess is if i leave it overnight
the first power on would not click.

I took some voltage measurements across some caps
the main 400v caps were going on and off and went to 385v

one of the caps showed a stable 5v
and another I think was the 3.3 which was going on and off.

[Diah]

Re: UE55F7000ST clicking on/off

show us focused high resolution photo of yours PCB from up and down side.. also any Voltage print chart on it as well the BL socket chart.

[shandy]

Re: UE55F7000ST clicking on/off

Hears the photos as requested, thanks

oops haven't done the downside yet will do after dinner thanks

[Diah]

Re: UE55F7000ST clicking on/off

Hears the photos as requested, thanks

oops haven't done the downside yet will do after dinner thanks

how about the down side of the boards.. !!!

[shandy]

Re: UE55F7000ST clicking on/off

here's the downside and another BL as the first one was a bit hidden by the sockets

[Diah]

Re: UE55F7000ST clicking on/off

Check solder joints.

+1
first you need not only check visually .. but its should clean old solder and resolver again all Transformer and relay too. start with hot area.. and always you check yours work by only plug the 2 sockets of BL to PCB and turn on.. when you have BL on and stay on you are done.

second you need to take all standing caps at hot area and measure its ESR , some caps leaking from down side not blowing at top.

[shandy]

Re: UE55F7000ST clicking on/off

OK, many thanks, I will take a much closer look and measure the ESR of
all the caps.

[nomoresonys]

Re: UE55F7000ST clicking on/off

also check every diode, diode mode should get a reading usually 555 or so some show more some less, then switch leads, should get l or I, report any that give a reading in both directions or shows short, check the 2 legged ones first, they have the little grey stripe, not to be confused with ferrite beads that don't have the stripe.

[shandy]

Re: UE55F7000ST clicking on/off

yes, will do that also, so far I’ve found a couple of small tantalum bead caps
with in circuit ESR of 6.8 ohm while others measure 0 I will take them out and
re measure out of circuit.

thanks again!

[shandy]

Re: UE55F7000ST clicking on/off

I am still looking, original problem remains

tested all electrolytic caps out of circuit, they tested ok with the ESR within
spec, the tantalum ones tested no ESR out of circuit.
tested all power gets and the 3 schottky rectifiers out of circuit
tested all smd transistors and fets they seem ok
tested all transformers

will do resistors next

[shandy]

Re: UE55F7000ST clicking on/off

Well it took a while all resistors appear in spec, I am now suspecting something with the main board. I found a youtube vid of a tech that disconnected a similar Samsung PS board from the main
board and that one clicked in sync with the BL leds going on and off also, he bridged two of the pins with a resistor and that kept the BL on, his socket was a bit different to mine so i’m a bit reluctant to try it.

I now am getting the standby led flashing on and off 2 times with 5 repetitions every time
with one of the tcon leds off

https://www.badcaps.net/forum/showthread.php?t=84791 this chap had the same TV and same problems as me but not sure if he fixed it.

[nomoresonys]

Re: UE55F7000ST clicking on/off

well since he gave no more feedback, my guess is the new tcon solved the problem.