Samsung tv blows fuse.un55eh6000f

[ronl]

Hi Members.I have this flat screen in for repair hopefully. The Power supply fuse is blown.i found out that the switching transistor is shorted so far.not sure if I can get parts for the power supply but a replacement board is available.usually at this point ,i pull out the schematic(don't have) and find out if something else overloaded the power supply before I replace anything.one common cause iirc, is the backlight arrays. Anybody know what voltage is needed and the current drawn by the backlights?. Power supply # is bn44-00499a.Thanks for any help. RonL

[ronl]

Hi Members.I just noticed tiny printing on the power supply board that give voltage outputs and current draw.im just wondering what does the forum think about my next step? I'm gonna use my external power supplys to check current loads to see of there is any problems with the rest of the set.( I did this with solid state crt tvs using switching power supplys,fly back derived voltages..etc.) Any tips on other troubleshooting efforts? If things check out,then I can order another power supply knowing that nothing else blew the supply. Thanks for any tips. RonL

[kf4rca]

My experience with a LG 50pg plasma RSF (roadside find). Had a blown fuse on the AC line input. Started checking around and both switcher MOSFETs were shorted.
I was able to get replacements locally for about $7 each. NOW, what else is blown?
Went thru the board with an ohmmeter and could find no other shorts.
BUT, what about the switcher chip? It was a strange Chinese number. The only source was Ebay and from China.
SO, I desoldered it and checked it all the way around for shorts. Couldn't find any.
Put it back in with the assumption it was OK.
Powered it up and it worked! Sometimes you get lucky.
Good luck!

[ronl]

Hi Members.getting ready to test the led backlights.Power board (bn44-00499a) states leds take 331volts,289ma.the plug(cn802) for the leds is labeled pin1,2=d1+,pin4=d1-,pin6=d2-+' and pin8,9=d2-. Are these led arrays wired in series?should the external power supply be connected to them in series( power supply negative connected to pin8,9 d2-- and positive be connected to pin1,2 d1 + with pin4,6 connected together?I have to check if pin4,6 are already connected through led array. I will use a variable supply ,monitoring current draw. Thanks for any input. RonL

[kf4rca]

Did you replace the shorted switching transistor?
I have never seen backlights blow a fuse.

[ronl]

Hi kf4rca. I made a mistake following the traces on the power board. The part that is shorted is a diode with 3 connections.( with some research i found the actual number of the part is byv25d600). I checked the switching transistors ( part # sanded off) and they are ok. This is a good buddy's set so ill talk to him about getting the part since I feel there is still a risk of other problems.I'm sure he will go for it since its not a lot of money.If more problems then he will buy a replacement set. https://www.amazon.ca/Fast-Recovery-...s%2C624&sr=8-1 RonL

[kf4rca]

Did you check that diode in-circuit or out-of-circuit?
If it read short in-circuit, you are reading thru the secondary winding of the transformer.

[ronl]

Hi kf4rca.diode was checked out of Circuit and is definitely shorted.just wondering if some other problem took it out? Didnt find any burnt resistors or signs of overheating/ excessive current.gonna do a check of electrolytic caps with my esr meter. RonL

[ronl]

Hi Kf4rca.I found more shorted fets and diodes. I tested the backlight led array.applied 331 vdc,monitored current and it drew less than the 284 ma stated in the power board.looks like power board blew on its own.I'm gonna advise my buddy that a replacement board should get his tv working again.can't find any other faults other than the power board. Its up to my buddy to decide if he wants to spend the money. Thanks for all your advice. RonL

[kf4rca]

Its a 55" so its probably worth fixing. How old is it? I'd be cautious about buying an Ebay board. It may be no better than the one you have. I looked around and could find no schematics for it.

[ronl]

Its a 2012 model.I found a few power supply boards ranging from $35 Canadian to $100. Some used( not the best choice imho) and new( more money).All were from parts companys in Canada.no ebay.Its up to my buddy to decide now.RonL

[ronl]

My Buddy decided on a used replacement power board available at a supplier in Canada.total price including shipping was $78 Canadian.2 transformers on the board smelled like they were stressed.talked to supplier and another board was shipped free of charge.unfortunately,same smell.I'm guessing most used power boards of this model smell after a few years of operation. Power board has a 6 month guarantee so my buddy decided "good enough". Installed and tested tv for a few days with no problems. Tv was picked up and my buddy is happy so it worked out. RonL