Samsung LN55C750 PSB

[gusalot]

Hi everybody. One of the capacitors on the PSB, BN44-00342b, for my TV recently went up in smoke. Usually the electrolytic caps go on these boards, but this was a ceramic cap, 220pf 1kv. I checked the diodes, checked the other caps. Everything was good. The display went dark; still the audio was working. I replaced the defective cap for $.38; thanks Digi-key. TV is back up and running. Has anybody seen anything like this. Thanks

[Techbill]

Re: Samsung LN55C750 PSB

I have seen these go in the inverter section, shutting down the inverter, sometimes blowing fuse or transistor, diode. Not seen as often in the primary of the power supply as in your case. If I am interpreting your picture correctly.

[billybob1944]

Re: Samsung LN55C750 PSB

i just had the exact capacitor blow in my 55" samsung was looking around trying to find what the exact capacitor to order to try fixing it

im glad i found your post and im glad to hear that it worked for you

mine was burnt out so bad i could read the rating on it so i was going to guess based on the other ratings on the rest of the board

[budm]

Re: Samsung LN55C750 PSB

Common failure, it is high voltage snubber cap, I replace them with higher voltage.

[lexo]

Re: Samsung LN55C750 PSB

Hi everybody. One of the capacitors on the PSB, BN44-00342b, for my TV recently went up in smoke. Usually the electrolytic caps go on these boards, but this was a ceramic cap, 220pf 1kv. I checked the diodes, checked the other caps. Everything was good. The display went dark; still the audio was working. I replaced the defective cap for $.38; thanks Digi-key. TV is back up and running. Has anybody seen anything like this. Thanks

I have a similar issue but with the bigger green cap as attached, i am not sure about the ratings though, can you help?

[budm]

Re: Samsung LN55C750 PSB

That is not the cap, that is the Thermistor to limit the inrush current when TV is turned on, it may have failed by itself or there is shorted circuit which is more likely is the case for it to blow up like that. You need to check the Bridge rectifier and all those 3-pin devices mounted on the heatsink to see if any one of them shows very low resistance.
Thermistor NT801S P/N WTR15D050, 5 Ohms @25c.

[lexo]

Re: Samsung LN55C750 PSB

That is not the cap, that is the Thermistor to limit the inrush current when TV is turned on, it may have failed by itself or there is shorted circuit which is more likely is the case for it to blow up like that. You need to check the Bridge rectifier and all those 3-pin devices mounted on the heatsink to see if any one of them shows very low resistance.
Thermistor NT801S P/N WTR15D050, 5 Ohms @25c.

Tx Budm,
It seems that thermistor had hard time on that board as you c.
I will de-solder the bridge and check it now.
Regards,

[budm]

Re: Samsung LN55C750 PSB

Check the bridge and all the devices attached to the heatsink.

[lexo]

Re: Samsung LN55C750 PSB

Tx Budm,
It seems that thermistor had hard time on that board as you c.
I will de-solder the bridge and check it now.
Regards,

I just checked the bridge, it seems fine.
from the other hand which ever component was there is labeled HS805 and not NT801S. are we on the same wavelength here?
Tx Budm

[lexo]

Re: Samsung LN55C750 PSB

Hi everybody. One of the capacitors on the PSB, BN44-00342b, for my TV recently went up in smoke. Usually the electrolytic caps go on these boards, but this was a ceramic cap, 220pf 1kv. I checked the diodes, checked the other caps. Everything was good. The display went dark; still the audio was working. I replaced the defective cap for $.38; thanks Digi-key. TV is back up and running. Has anybody seen anything like this. Thanks

Hello Gusalot,
do you still have the TV? i have a thermistor that jumped, would you be able to find the rating on it?
Tx

[budm]

Re: Samsung LN55C750 PSB

I just checked the bridge, it seems fine.
from the other hand which ever component was there is labeled HS805 and not NT801S. are we on the same wavelength here?
Tx Budm

You ned to remove that white glue to see the designator on the board. HS805 is the designator for the heatsink.

[lexo]

Re: Samsung LN55C750 PSB

You ned to remove that white glue to see the designator on the board. HS805 is the designator for the heatsink.

Dear Budm,
Thank you very much for your help, i followed your instructions after checking all the components on the heatsink, it turned out only the thermistor is dead, replaced it with a new one and now i am watching TV.
Tx guys,
keep up the good work and know-how transfer