Samsung ln40d550k1fxza

[triplefour]

got this TV for 10 bux because it doesnt turn on. no standby light, no standby voltage.
i noticed that one of the big ceramic fuses tests as open.
so i replaced it with another ceramic fuse from a dead PC power supply i had lying around. when i plugged in the TV, not even a second later i heard a loud pop and thought i saw spark even at the fuse i just replaced. also it looked like the fuse got cracked or damaged in some way.
i assumed the TV had blown the fuse just like it blew the one before it but when i checked with my meter, the fuse is still OK!
so what popped then?
the original fuse says T3.15AH250V but the one i replaced with just says 250V on it. what does the 3.15AH mean? is it possible i used the wrong fuse and blew something else up?
also i notice now that it takes forever for the main filter cap on the right to discharge itself. the one on the left discharges in a couple minutes but the one on the right takes a really long time! i didnt really test this before changing the fuse though so im not sure. but i think i remember it draining pretty fast because i was able to change the fuse without waiting forever.

[tom66]

Re: Samsung ln40d550k1fxza

3.15A is the current rating of the fuse. You MUST replace the fuse with a 3.15A fuse or damage/further problems could occur.

[triplefour]

Re: Samsung ln40d550k1fxza

ah dang well the one i replaced it with said 10A on it...live and learn.. i thought all those ceramic fuses were the same for some reason. guess ill have to get a 3.15A to see if i did any other damage...

[tom66]

Re: Samsung ln40d550k1fxza

Well, if the fuse didn't blow, and you haven't put any craters in any devices... you should be OK. However you MUST NOT run the board with that fuse, until you get the new one.

[Neelix]

Re: Samsung ln40d550k1fxza

BTW, the AH after the current rating of the fuse means that the body of the fuse is of ceramic type. If AL then it means glass type

[triplefour]

Re: Samsung ln40d550k1fxza

thanks, i was wondering about that. yeah the fuse didnt blow but something else made a loud pop noise and sparked. i tried testing diodes around that area and they seem fine. but i guess i wont know till i find one of these fuses...radioshack or ebay??
on ebay i see slow blow and fast blow fuses that have these same values. where on my fuse does it tell if its slow or fast blowing?

[tom66]

Re: Samsung ln40d550k1fxza

You have probably caused a lot more damage to the power board. Maybe best just to replace it. You should not just replace a mains fuse without identifying original failure... too much risk of damage.

[triplefour]

Re: Samsung ln40d550k1fxza

how do i go about identifying the original failure if i cant see any obvious damage? dont i need to get the tv at least powered on to see voltages? i would like to learn about the SMPS in detail by trying to fix this one... and fuses are cheap so i dont have much to lose. ive gotta at least try. i cant even find a replacement PSU on ebay...

[elviramjw]

Re: Samsung ln40d550k1fxza

T3.15AH250V

The T means its a time delay fuse (Slow Blow)

[budm]

Re: Samsung ln40d550k1fxza

You should make one of this to put the lamp in series with the load.
http://s807.photobucket.com/user/bud...tml?sort=3&o=0
http://s807.photobucket.com/user/bud...tml?sort=3&o=1
http://s807.photobucket.com/user/bud...tml?sort=3&o=3
And GFCI outlet for safety:
http://s807.photobucket.com/user/bud...tml?sort=3&o=7
And Isolation transformer for safety.

[triplefour]

Re: Samsung ln40d550k1fxza

looks cool but its a bit over my head. is there anywhere that explains what this is, what it does, and how to make it? not sure i can figure it all out just from those pictures :/

[budm]

Re: Samsung ln40d550k1fxza

It basically put the light bulb in series with the load, if the load has shorted circuit or draw too much current, the lamp will light up and limit the current flowing through the load without blowing up the new parts you just installed, and it will also tell you that you still have shorted or bad circuits if the lamp stay on and brightly lit, Or you can keep popping in the new fuses and hope that there is no shorts or active shorts in the circuits.

[triplefour]

Re: Samsung ln40d550k1fxza

so its a thing to save my fuses...i am definitely interested but at this stage in my education i need detailed instructions to build something like that. so much to learn!

[budm]

Re: Samsung ln40d550k1fxza

"so its a thing to save my fuses" that is not the main reason, it is to safe the circuits from further damages, and the new part you put in, for example, you found power MOSFET that shorted out or blown up, and you just going to put the new one in without changing or the IC that drive the MOSFET, if the IC is also damaged, you will just blow up the new MOSFET, the lamp will light up brightly and stay bright, that means you still have bad parts on the board, in this case, the output of the bad IC that you did not replace is stuck high instead of switching on and off at high frequency.
If you understand how the circuits function then you will know what to expect and what will happen. I am learning and try to understand how the circuits and components function everyday, there is no end in learning electronics, there are new circuits and components being designed every day.

[triplefour]

Re: Samsung ln40d550k1fxza

oh ok...so you install the lamp tester thing (what do you call this device?) in place of where the new part would go? is there any chance the bulb will blow up?

[budm]

Re: Samsung ln40d550k1fxza

You plug what you are working on into the outlet on the box.

[triplefour]

Re: Samsung ln40d550k1fxza

ok so u install the new part, and then plug the tv into this magic outlet with some bulbs on it, and instead of your part blowing up, the bulbs blow up...or glow brightly? sorry i know thats probly not what happens but im having trouble following exactly...

if the tv is working properly, the bulb will not light up at all?

after reading ur words and staring at the pictures its starting to make some sense

[budm]

Re: Samsung ln40d550k1fxza

Lamp does not blow up, it is 120V lamp, if the circuit is good, the lamp will light up brightly for section during the main filter cap being charged, then the lamp will dim down if there is not current over load or shorts circuit. The Wattage of the lamp is selected based on the power consumption of the unit you are working on.
There are many info out there.

http://www.repairfaq.org/samnew/tvfaq/tvtslbt.htm
http://www.radiomuseum.org/forum/cur...lb_tester.html
http://pontoppidan.info/lars/index.p...stories&page=5

[triplefour]

Re: Samsung ln40d550k1fxza

thanks budm, i think i understand now.
i will try to make this device. in the meantime though, i might just find another fuse and try my luck

[triplefour]

Re: Samsung ln40d550k1fxza

well i managed to find one of the correct fuses laying around so i put it in. it didnt spark this time, and now when i plug in the set i get the standby light blinking 5 times then going off. when i push power the standby light comes on and stays on but i have no backlights. the voltages to the inverter are really low. probably because the tv isnt actually able to turn on, its just stuck in 5v standby. i really think by putting in that wrong fuse i may have damaged something else. to think i might have had a fully working tv with just replacing the fuse if i had got it right! never again will i make this mistake! but since i did... can anyone help me trace down what might have blown? i already checked all the diodes in that area and they seem fine... maybe the transformer, or the mosfets that have the heatsinks on them?