Samsung LE40B652T4WXXU Screnn flicker now black screen

[london-freddie]

Hi All
new to this site asking for help or advice
got a Samsung LE40B652T4WXXU HD TV
power board fitted is BN44-00264A
TV worked fine, however was suffering from very bad screen flickering
If backlight was set high ie 10 screen would flicker bad until backlight/ picture would go off after a while, sound was still ok
If backlight was set low ie 1 to 5 screen was fine however dark tv would stay on all day
Last night whilst watching tv screen went black, backlights off, sound working ok, all other functions seem to work.
when switching tv on now screen sometimes lights for maybe 1 second then goes off
I am convinced this is a power board/inverter problem, and have replaced all caps on the power board, result still the same.
need help now anyone any ideas what to look for and check now
have googled this seems to be a common fault on this set but found nothing as to what is the problem with it

thanks in anticipation

[newtothis]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Pictures of boards and chassis.

I am going to take a guess at the LED's being bad, We see it all to often these days

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Trying to upload some pictures now
However prior to black screen picture was very good with no shadows suggesting to me one or more of the backlight tubes was not working, I may be wrong though

[newtothis]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

These are LED and not FL Tubes.

We see so often that an LED on the strips goes bad and causes this fault

[flocko]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

These power board do suffer with bad inverter transformers resistance check each one and compare? Flocko

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

trying to find where my pictures I have posted have gone to

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

can anyone point me how to test these transformers 4 of them and what to look for please

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

anyone???

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Check the DCV between the two legs of the main filter cap to see if it has >360VDC when TV is turned on.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

yes got dcv at main filter cap
also changed fan7530
still backlight switching off after 1-2 seconds

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

anyone know how to disable the protection on this power board BN44-00264A, to force backlights to stay on to see if all backlight lamps are lit

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

inverter transformers appear to check out ok

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

yes got dcv at main filter cap
also changed fan7530
still backlight switching off after 1-2 seconds

I am sure you are getting the DCV on the main cap, But are you getting the boosted Voltage above 360VDC?

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

SEM2006 spec sheet.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

thanks for the reply, however not sure what you mean, am I measuring voltage at legs of CP815 & 816, large blue caps

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

thanks for the reply, however not sure what you mean, am I measuring voltage at legs of CP815 & 816, large blue caps

Those are the two caps, they are connected in parallel, so what is the Voltage reading between the two legs of the CP815 when TV is off and when TV's power switch is activated?
Post #10: "yes got dcv at main filter cap" You never tell us what the Voltage reading is.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

401v at cp815 with set switched on

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

Good the PFC Voltage booster is working.
Check the capacitance of cap CI892 (0.47uf 400V, SCH page 2).
We also need to check the resistance of the High Voltage windings of the inverter transformers.

[london-freddie]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

how do I test c1892 I do not have a cap tester

[budm]

Re: Samsung LE40B652T4WXXU Screnn flicker now black screen

You need capacitance meter to check its capacitance, but for now you can check the resistance of the inverter transformer high Voltage windings.