Samsung LE32B350F No backlights & Flashing LED

[Davy]

Have Samsung LE32B350F telly with no backlights and flashing LED.... Ok could be the CCFL's I know.

All voltages are up and running except the 'fault detect pin' at pin 14,  am I right in thinking this should be 5 Volts when running, from standby it rises from about  0.01V to only 0.1V or so - should it not kick up to 5V then trip and the die down othewise the CCFL's are never going to ignite?

Strange thing is that I was told it made a funny noise as it tried to switch on - the only noise I could hear was the Samsung chime. I'm wondering if this funny noise could be the inverter transformers 'singing'... or the CCFL's arcing - seen that a time or two where the tubes crack at the ends and then arc away.

The power supply also carry's the inverter and make's it harder get at the tubes as the board slides into the tube's HV connectors.... knocking on a bit I suppose so could well be the tubes but 5V don't seem to kick up on the fault detect pin.

Dave

[downunder]

Hi Dave, depends on design, I guess, but I'd expect the error detect pin would go high in the event of a CCFL failure being detected. Have you checked the "fingers" on the inverter board where they connect with the ccfls for arcing. Also check the secondary windings of the inverter transformers - usually in the order of 1.5 to 2 k.ohms. If one differs markedly from the others, it is deemed as being faulty. Otherwise it's a strip job to check the actual CCFL tubes.            Bruce.

[Davy]

Hi Bruce,
Yes thats one of the thing's I checked.... I do think "a funny noise at switch on" is a clue - sounds something like that doesn't it? Certainly makes no noise for me except for Samsung chime tellig me dinner is ready.

I'll take another look..... since I just been told it's a 'scrapper' I'll bisect the 5Volt fault detect supply on  pin 14  and shove something up via 220 Ohm resistor or so.... if ya' see the moon with two faces give us a wave!

Somethings not adding up in my book here in standby I get about 10mV and it rises to about 150mV no signs of excess voltage, it should be 5V one way or the other.

Made in Hungary it said on the back, the power board in question is a Hanaro3

If it is the transfomers..... is it worth it I ask because the CCFL's won't be in their prime, looking at the serial number the set was made in 2009?

How to decode Samsung serial numbers https://technastic.com/samsung-tv-serial-number-explained/

Dave

[michael first]

hi, Dave
did you check up the voltage of the PFC stage?is it up to 385V?if not the culprit could be right there.just a thought   

[Davy]

I was told to scrap it, so I did. Yes the PFC voltage was there.
Thanks and sorry for late response

Dave